Antidepressant fluoxetine enhances glucocorticoid receptor function in vitro by modulating membrane steroid transporters

The efficacy of citalopram or escitalopram in patients with asthma and major depressive disorder

BACKGROUND

Major depressive disorder is common in people with asthma. Yet, few studies have evaluated depression treatment in those with asthma.

OBJECTIVE

To explore the relationship between antidepressant use, depressive symptoms, and asthma control, pooled data from 3 randomized trials of either citalopram or escitalopram were assessed.

METHODS

Linear fixed effects and binary logistic regression analyses were conducted with between-subject covariates including treatment group, (original) study, and demographics. The within-subject effect of visit, and a treatment group-visit (between-within) interaction effect, were also evaluated. Analyses were repeated in a high asthma exacerbation subgroup having at least 3 oral corticosteroid bursts in the previous 12 months. Outcomes included the Hamilton rating scale for depression (HAM-D17), the 7-item asthma control questionnaire (ACQ), and oral corticosteroid use (yes or no).

RESULTS

In the pooled sample (n = 255), the antidepressant treatment group exhibited lower HAM-D17 overall (P ≤ .001) and a lower likelihood for oral corticosteroid use (P ≤ .001) relative to the placebo group. In the high-exacerbation subgroup (n = 96), treatment group participants had lower overall asthma control questionnaire (P = .004) and HAM-D17 scores (P ≤ .001), and a lower likelihood of oral corticosteroid use (P = .003), relative to placebo participants. All treatment group interaction effects were not significant.

CONCLUSION

Citalopram or escitalopram exhibited efficacy in reducing depressive symptoms and the need for rescue oral corticosteroids in patients with asthma and major depressive disorder. Future work should determine whether selective serotonin reuptake inhibitors are effective at improving asthma outcomes in those with asthma who are not depressed.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT00621946 and NCT01324700 (one study was conducted before ClinicalTrials.gov requirements).

Selective Targeting of Lung Cancer Cells with Methylparaben-Tethered-Quinidine Cocrystals in 3D Spheroid Models

The development and design of pharmaceutical cocrystals for various biological applications has garnered significant interest. In this study, we have established methodologies for the growth of the methylparaben-quinidine cocrystal (MP-QU), which exhibits a well-defined order that favors structure-property correlation. To confirm the cocrystal formation, we subjected the cocrystals to various physicochemical analyses such as powder X-ray diffraction (PXRD), single-crystal X-ray diffraction (SCXRD), Raman, and IR spectroscopy. The results of the XRD pattern comparisons indicated no polymorphisms, and density functional theory (DFT) studies in both gaseous and liquid phases revealed enhanced stability. Our in silico docking studies demonstrated the cocrystal's high-affinity binding towards cancer-specific epidermal growth factor receptor (EGFR), Janus kinase (JAK), and other receptors. Furthermore, in vitro testing against three-dimensional (3D) spheroids of lung cancer (A549) and normal fibroblast cells (L929) demonstrated the cocrystal's higher anticancer potential, supported by cell viability measurements and live/dead assays. Interestingly, the cocrystal showed selectivity between cancerous and normal 3D spheroids. We found that the MP-QU cocrystal inhibited migration and invadopodia formation of cancer spheroids in a favorable 3D microenvironment.

Therapeutic treatment with fluoxetine using the chronic unpredictable stress model induces changes in neurotransmitters and circulating miRNAs in extracellular vesicles

The most widely prescribed antidepressant, fluoxetine (FLX), is known for its antioxidant and anti-inflammatory effects when administered post-stress. Few studies have evaluated the effects of FLX treatment when chronic stress has induced deleterious effects in patients. Our objective was to evaluate FLX treatment (20 mg/kg/day, i.v.) once these effects are manifested, and the drug's relation to extracellular circulating microRNAs associated with inflammation, a hedonic response (sucrose intake), the forced swim test (FST), and corticosterone levels (CORT) and monoamine concentrations in limbic areas. A group of Wistar rats was divided into groups: Control; FLX; CUMS (for six weeks of exposure to chronic, unpredictable mild stress); and CUMS + FLX, a mixed group. After CUMS, the rats performed the FST, and serum levels of CORT and six microRNAs (miR-16, -21, -144, -155, -146a, -223) were analyzed, as were levels of dopamine, noradrenaline, and serotonin in the prefrontal cortex, hippocampus, and hypothalamus. CUMS reduced body weight, sucrose intake, and hippocampal noradrenaline levels, but increased CORT, immobility behavior on the FST, dopamine concentrations in the prefrontal cortex, and all miRNAs except miR-146a expression. Administering FLX during CUMS reduced CORT levels and immobility behavior on the FST and increased the expression of miR-16, -21, -146a, -223, and dopamine. FLX protects against the deleterious effects of stress by reducing CORT and has an antidepressant effect on the FST, with minimally-modified neurotransmitter levels. FLX increased the expression of miRNAs as part of the antidepressant effect. It also regulates both neuroinflammation and serotoninergic neurotransmission through miRNAs, such as the miR-16.

Effect of lurasidone treatment on chronic mild stress-induced behavioural deficits in male rats: The potential role for glucocorticoid receptor signalling

BACKGROUND

Stress represents one of the main precipitating factors for psychiatric diseases, characterised by an altered function of glucocorticoid receptors (GR), known to play a role in mood and cognitive function. We investigated the ability of the antipsychotic lurasidone to modulate the involvement of genomic and non-genomic GR signalling in the behavioural alterations due to chronic stress exposure.

METHODS

Male Wistar rats were exposed to seven weeks of chronic mild stress (CMS) and treated with lurasidone (3 mg/kg/day) starting from the second week of stress for more five weeks. Gene expression and protein analyses were conducted in dorsal hippocampus.

RESULTS

Seven weeks of CMS induced anhedonia and cognitive impairment, which were normalised by lurasidone. At molecular level, CMS rats showed an increase of GR protein levels by 60% (p<0.001 vs. CTRL/VEH) in the membrane compartment, which was paralleled by an up-regulation of phosphoSINAPSYN Ia/b by 88% (p<0.01 vs. CTRL/VEH) and of the mitochondrial marker Cox3 by 21% (p<0.05 vs. CTRL/VEH). Moreover, while exposure to the novel object recognition test increased the nuclear translocation of GRs by 96% (p<0.01 vs. CTRL/VEH/Naïve) and their transcriptional activity in non-stressed rats, such mechanisms were impaired in CMS rats. Interestingly, the genomic and non-genomic alterations of GR, induced by CMS, were normalised by lurasidone.

CONCLUSION

Our results further support the role of glucocorticoid signalling in the dysfunction associated with stress exposure. We provide novel insights on the mechanism of lurasidone, suggesting its effectiveness on different domains associated with psychiatric disorders.

Desipramine restores the alterations in circadian entrainment induced by prenatal exposure to glucocorticoids

Alterations in circadian rhythms are closely linked to depression, and we have shown earlier that progressive alterations in circadian entrainment precede the onset of depression in mice exposed in utero to excess glucocorticoids. The aim of this study was to investigate whether treatment with the noradrenaline reuptake inhibitor desipramine (DMI) could restore the alterations in circadian entrainment and prevent the onset of depression-like behavior. C57Bl/6 mice were exposed to dexamethasone (DEX-synthetic glucocorticoid analog, 0.05 mg/kg/day) between gestational day 14 and delivery. Male offspring aged 6 months (mo) were treated with DMI (10 mg/kg/day in drinking water) for at least 21 days before behavioral testing. We recorded spontaneous activity using the TraffiCage™ system and found that DEX mice re-entrained faster than controls after an abrupt advance in light-dark cycle by 6 h, while DMI treatment significantly delayed re-entrainment. Next we assessed the synchronization of peripheral oscillators with the central clock (located in the suprachiasmatic nucleus-SCN), as well as the mechanisms required for entrainment. We found that photic entrainment of the SCN was apparently preserved in DEX mice, but the expression of clock genes in the hippocampus was not synchronized with the light-dark cycle. This was associated with downregulated mRNA expression for arginine vasopressin (AVP; the main molecular output entraining peripheral clocks) in the SCN, and for glucocorticoid receptor (GR; required for the negative feedback loop regulating glucocorticoid secretion) in the hippocampus. DMI treatment restored the mRNA expression of AVP in the SCN and enhanced GR-mediated signaling by upregulating GR expression and nuclear translocation in the hippocampus. Furthermore, DMI treatment at 6 mo prevented the onset of depression-like behavior and the associated alterations in neurogenesis in 12-mo-old DEX mice. Taken together, our data indicate that DMI treatment enhances GR-mediated signaling and restores the synchronization of peripheral clocks with the SCN and support the hypothesis that altered circadian entrainment is a modifiable risk factor for depression.

Chronic Glucocorticoid Exposure Induces Depression-Like Phenotype in Rhesus Macaque (Macaca Mulatta)

It has long been observed in humans that the occurrence of depressive symptoms is often accompanied by the dysfunction of hypothalamic-pituitary-adrenal (HPA) axis. The rodent experiments also showed that chronic corticosterone exposure could induce depression-like phenotype. However, rodents are phylogenetically distant from humans. In contrast, non-human primates bear stronger similarities with humans, suggesting research on primates would provide an important complement. For the first time, we investigated the effects of chronic glucocorticoid exposure on rhesus macaques. Seven male macaques were selected and randomized to glucocorticoid or vehicle groups, which were subjected to either prednisolone acetate or saline injections, respectively. The depression-like behaviors were assessed weekly, and the body weights, HPA axis reactivity, sucrose solution consumption and monoaminergic neurotransmitters were further compared between these two groups. The glucocorticoid group was not found to display more depression-like behaviors than the vehicle group until 7 weeks after treatment. Chronic glucocorticoid exposure significantly decreased the levels of cortisol determined from blood (a biomarker for acute HPA axis reactivity) but increased the hair cortisol concentrations (a reliable indicator of chronic HPA axis reactivity) compared with controls. The glucocorticoid group was also found to consume less sucrose solution than controls, a good manifestation of anhedonia. This could be possibly explained by lower dopamine (DA) levels in cerebrospinal fluid induced by chronic glucocorticoid treatment. The results presented here indicate that chronic glucocorticoid exposure could disturb both the acute and chronic HPA axis reactivity, which eventually disturbed the neurotransmitter system and led monkeys to display depression-like phenotype.

Ketamine improved depressive-like behaviors via hippocampal glucocorticoid receptor in chronic stress induced- susceptible mice

Chronic stress is an important factor for depression. Most individuals recover from stress, while some develop into depression. The pathogenesis of resilience or susceptibility remains unclear. Stress activates the hypothalamic-pituitary-adrenal (HPA) axis and releases stress hormones to regulate individual response to stress. Hence, we assessed the effects of chronic social defeat stress (CSDS) on susceptible behaviors, plasma corticosterone (CORT) concentration, glucocorticoid receptor (GR) expressions in hippocampus and medial prefrontal cortex (mPFC). Mice that plasma CORT concentration is increased 2 h after single social defeat stress developed into susceptible mice after 10 d social defeat stress. The plasma CORT concentration was still higher than that of resilient mice 48 h after the last defeat stress. Mice administered CORT via drinking water showed susceptibility. Mifepristone, a GR antagonist improved susceptibility to chronic stress. Single dose ketamine treatment improved depressive-like behaviors, decreased plasma CORT concentration, rescued GR expression and nuclear translocation in the hippocampus of susceptible mice. These results suggested that abnormal CORT concentration after stress may predict susceptibility to depression in clinic. Ketamine may exert the antidepressant effect via normalizing HPA axis response and have significance in the clinic.

Checks and balances: The glucocorticoid receptor and NFĸB in good times and bad

Mutual regulation and balance between the endocrine and immune systems facilitate an organism's stress response and are impaired following chronic stress or prolonged immune activation. Concurrent alterations in stress physiology and immunity are increasingly recognized as contributing factors to several stress-linked neuropsychiatric disorders including depression, anxiety, and post-traumatic stress disorder. Accumulating evidence suggests that impaired balance and crosstalk between the glucocorticoid receptor (GR) and nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) - effectors of the stress and immune axes, respectively - may play a key role in mediating the harmful effects of chronic stress on mood and behavior. Here, we first review the molecular mechanisms of GR and NFκB interactions in health, then describe potential shifts in the GR-NFκB dynamics in chronic stress conditions within the context of brain circuitry relevant to neuropsychiatric diseases. Furthermore, we discuss developmental influences and sex differences in the regulation of these two transcription factors.

Why are depressed patients inflamed? A reflection on 20 years of research on depression, glucocorticoid resistance and inflammation

Studies over the last 20 years have demonstrated that increased inflammation and hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis are two of the most consistent biological findings in major depression and are often associated: but the molecular and clinical mechanisms underlying these abnormalities are still unclear. These findings are particularly enigmatic, especially considering the accepted notion that high levels of cortisol have an anti-inflammatory action, and therefore the coexistence of inflammation and hypercortisolemia in the same diagnostic group appears counter-intuitive. To celebrate the 2015 Anna-Monika Foundation Award to our laboratory, this review will discuss our own 20 years of research on the clinical and molecular evidence underlying the increased inflammation in depression, especially in the context of a hyperactive HPA axis, and discuss its implications for the pathogenesis and treatment of this disorder.

Chronic distress and the vulnerable host: a new target for HIV treatment and prevention?

Pathologic stress (distress) disturbs immune, cardiovascular, metabolic, and behavioral homeostasis. Individuals living with HIV and those at risk are vulnerable to stress disorders. Corticotropin-releasing hormone (CRH) is critical in neuroendocrine immune regulation. CRH, a neuropeptide, is distributed in the central and peripheral nervous systems and acts principally on CRH receptor type 1 (CRHR1). CRH in the brain modulates neuropsychiatric disorders. CRH and stress modulation of immunity is two-pronged; there is a direct action on hypothalamic-pituitary-adrenal secretion of glucocorticoids and through immune organ sympathetic innervation. CRH is a central and systemic proinflammatory cytokine. Glucocorticoids and their receptors have gene regulatory actions on viral replication and cause central and systemic immune suppression. CRH and stress activation contributes to central nervous system (CNS) viral entry important in HIV-associated neurocognitive disorders and HIV-associated dementia. CNS CRH overproduction short-circuits reward, executive, and emotional control, leading to addiction, cognitive impairment, and psychiatric comorbidity. CRHR1 is an important therapeutic target for medication development. CRHR1 antagonist clinical trials have focused on psychiatric disorders with little attention paid to neuroendocrine immune disorders. Studies of those with HIV and those at risk show that concurrent stress-related disorders contribute to higher morbidity and mortality; stress-related conditions, addiction, immune dysfunction, and comorbid psychiatric illness all increase HIV transmission. Neuropsychiatric disease, chronic inflammation, and substance abuse are endemic, and chronic distress is a pathologic factor. It is being understood that stress and CRH are fundamental to neuroendocrine immunity; therapeutic interventions with existing and novel agents hold promise for restoring homeostasis, reducing morbidity and mortality for those with HIV and possibly reducing future disease transmission.

Fluoxetine Increases the Expression of miR-572 and miR-663a in Human Neuroblastoma Cell Lines

Evidence suggests neuroprotective effects of fluoxetine, a selective serotonin reuptake inhibitor (SSRI), on the developed neurons in the adult brain. In contrast, the drug may be deleterious to immature or undifferentiated neural cells, although the mechanism is unclear. Recent investigations have suggested that microRNAs (miRNA) may be critical for effectiveness of psychotropic drugs including SSRI. We investigated whether fluoxetine could modulate expressions of neurologically relevant miRNAs in two neuroblastoma SK-N-SH and SH-SY5Y cell lines. Initial screening results revealed that three (miR-489, miR-572 and miR-663a) and four (miR-320a, miR-489, miR-572 and miR-663a) miRNAs were up-regulated in SK-N-SH cells and SH-SY5Y cells, respectively, after 24 hours treatment of fluoxetine (1–25 μM). Cell viability was reduced according to the dose of fluoxetine. The upregulation of miR-572 and miR-663a was consistent in both the SH-SY5Y and SK-N-SH cells, confirmed by a larger scale culture condition. Our data is the first in vitro evidence that fluoxetine could increase the expression of miRNAs in undifferentiated neural cells, and that putative target genes of those miRNAs have been shown to be involved in fundamental neurodevelopmental processes.

Stress-induced mechanisms in mental illness: A role for glucocorticoid signalling

Stress represents the main environmental risk factor for mental illness. Exposure to stressful events, particularly early in life, has been associated with increased incidence and susceptibility of major depressive disorders as well as of other psychiatric illnesses. Among the key players in these events are glucocorticoid receptors. Dysfunctional glucocorticoid signalling may indeed contribute to psychopathology through a number of mechanisms that regulate the response to acute or chronic stress and that affect the function of genes and systems known to be relevant for mood disorders. Indeed, exposure to chronic stress early in life as well as in adulthood has been shown to reduce the expression of glucocorticoid receptors (GR), also through epigenetic mechanisms, and to up-regulate the expression of the co-chaperone gene FKBP5, which restrains GR activity by limiting the translocation of the receptor complex to the nucleus. Another mechanism that contributes to changes in GR responsiveness is the state of receptor phosphorylation that controls activation, subcellular localization as well as its transcriptional activity. Moreover, GR phosphorylation may represent an important mechanism for the cross talk between neurotrophic signalling and GR-dependent transcription, bridging two important players for mood disorders. One gene that lies downstream from GR and may contribute to stress-related changes is serum glucocorticoid kinase-1 (SGK1). We have demonstrated that the expression of SGK1 is significantly increased after exposure to chronic stress in rodents as well as in the blood of drug-free depressed patients. We have also shown that SGK1 up-regulation may ultimately reduce hippocampal neurogenesis and contribute to the structural abnormalities that have been reported to occur in depressed patients. In summary, GR signalling may represent a point of convergence as well as of divergence for defects associated with pathologic conditions characterized by heightened vulnerability to stress. The characterization of these abnormalities is crucial to identify novel targets for therapeutic intervention that may counteract more effectively stress-induced neurobiological abnormalities.

Decline of hippocampal stress reactivity and neuronal ensemble coherence in a mouse model of depression

Dysregulations of stress systems, especially the hypothalamo-pituitary-adrenal (HPA) axis, have been commonly reported in major depression. Consistent results emphasized the role of the hippocampus in regulating stress systems and restoring an operative control on HPA axis following antidepressant treatments. However, very little is known about how the hippocampus integrates stress-related information and reacts to stressors beforehand. We therefore aimed to assess activations of hippocampal neuronal ensembles during stress-related experiences and evaluated the effects of a mouse model of depression, the Unpredictable Chronic Mild Stress (UCMS), and an antidepressant treatment (fluoxetine, 20mgkg(-1)day(-1), ip) in BALB/cByJ mice. The UCMS induced a depression-like syndrome characterized by a reduced weight gain, a progressive deterioration of the coat, an altered stress-coping strategy in behavioural tests and HPA axis dysregulations. Chronic fluoxetine had no effect in control non-stressed mice per se but reversed the syndrome induced by the UCMS, including an improvement of the HPA-system alterations. Neuronal activation was then assessed by immediate early-gene (c-fos) expression in different subfields of the CA3 and dentate gyrus (DG) along the dorso-ventral axis of the hippocampus, as they can support different computational functions. Our results showed that the hippocampus reacts to stressors by adjusting activations of cell ensembles. A pre-treatment with dexamethasone (DEX), a glucocorticoid receptor (GR) agonist that produced a delayed inhibition of the HPA axis activity, reduced novelty-related activations in the proximal CA3 (CA3c) and the DG of the dorsal hippocampus. All these effects were compromised by the UCMS, particularly by altering activation coherences within the dorsal CA3-DG network, but were rescued by chronic fluoxetine. Our study indicates therefore that variations of CA3-DG cell ensemble activation may contribute to stress integration in the hippocampus and that dysfunctions of this process may foster HPA-system dysregulations and depression-related states. It suggests that pharmacological interventions aiming to consolidate CA3-DG neural network might improve stress reactivity and possibly benefit to patients with major depression.

Multilevel assessment of the neurobiological threat system in depressed adolescents: interplay between the limbic system and hypothalamic-pituitary-adrenal axis

Integrative, multilevel approaches investigating neurobiological systems relevant to threat detection promise to advance understanding of the pathophysiology of major depressive disorder (MDD). In this study we considered key neuronal and hormonal systems in adolescents with MDD and healthy controls (HC). The goals of this study were to identify group differences and to examine the association of neuronal and hormonal systems. MDD and HC adolescents (N = 79) aged 12-19 years were enrolled. Key brain measures included amygdala volume and amygdala activation to an emotion face-viewing task. Key hormone measures included cortisol levels during a social stress task and during the brain scan. MDD and HC adolescents showed group differences on amygdala functioning and patterns of cortisol levels. Amygdala activation in response to emotional stimuli was positively associated with cortisol responses. In addition, amygdala volume was correlated with cortisol responses, but the pattern differed in depressed versus healthy adolescents, most notably for unmedicated MDD adolescents. The findings highlight the value of using multilevel assessment strategies to enhance understanding of pathophysiology of adolescent MDD, particularly regarding how closely related biological threat systems function together while undergoing significant developmental shifts.

Depressive-like behaviours and decreased dendritic branching in the medial prefrontal cortex of mice with tumors: A novel validated model of cancer-induced depression

Depression is commonly comorbid in cancer patients and has detrimental effects on disease progression. Evidence suggests that biological mechanisms may induce the onset of cancer-induced depression (CID). The present investigation aims to establish a validated preclinical animal model of CID. Female BALB/c mice were allocated to four groups: control (n=12), chronic oral exposure to corticosterone (CORT) (n=12), CORT exposure followed by chronic low dose fluoxetine (FLX) treatment (n=12), and subcutaneous inoculation of 4T1 mammary carcinoma cells (n=13). Anhedonia was evaluated using the sucrose preference test (SPT), and behavioural despair was evaluated using the forced swim test (FST) and tail suspension test (TST). Sholl analyses were used to examine the dendritic morphology of Golgi-Cox impregnated neurons from the medial prefrontal cortex (mPFC). CORT exposure and tumor burden were both associated with decreased sucrose preference, increased FST immobility, and decreased basilar and apical dendritic branching of neurons in the mPFC. CORT-induced behavioural and dendritic morphological changes were reversible by FLX. No differences in TST immobility were observed between groups. On the secondary TST outcome measure, CORT exposure and tumor burden were associated with a trend towards decreased power of movement. CORT exposure induced a positive control model of a depressive-like state, with FLX treatment confirming the predictive validity of the model. This verified the sensitivity of behavioural and histological tests, which were used to assess the CID model. The induction of a depressive-like state in this model represents the first successfully validated animal model of CID.

Fluoxetine treatment ameliorates depression induced by perinatal arsenic exposure via a neurogenic mechanism

Several epidemiological studies have reported an association between arsenic exposure and increased rates of psychiatric disorders, including depression, in exposed populations. We have previously demonstrated that developmental exposure to low amounts of arsenic induces depression in adulthood along with several morphological and molecular aberrations, particularly associated with the hippocampus and the hypothalamic-pituitary-adrenal (HPA) axis. The extent and potential reversibility of this toxin-induced damage has not been characterized to date. In this study, we assessed the effects of fluoxetine, a selective serotonin reuptake inhibitor antidepressant, on adult animals exposed to arsenic during development. Perinatal arsenic exposure (PAE) induced depressive-like symptoms in a mild learned helplessness task and in the forced swim task after acute exposure to a predator odor (2,4,5-trimethylthiazoline, TMT). Chronic fluoxetine treatment prevented these behaviors in both tasks in arsenic-exposed animals and ameliorated arsenic-induced blunted stress responses, as measured by corticosterone (CORT) levels before and after TMT exposure. Morphologically, chronic fluoxetine treatment reversed deficits in adult hippocampal neurogenesis (AHN) after PAE, specifically differentiation and survival of neural progenitor cells. Protein expression of BDNF, CREB, the glucocorticoid receptor (GR), and HDAC2 was significantly increased in the dentate gyrus of arsenic animals after fluoxetine treatment. This study demonstrates that damage induced by perinatal arsenic exposure is reversible with chronic fluoxetine treatment resulting in restored resiliency to depression via a neurogenic mechanism.

Effect of selective serotonin reuptake inhibitors and immunomodulator on cytokines levels: an alternative therapy for patients with major depressive disorder

Major depressive disorder (MDD) is a psychiatric illness that presents as a deficit of serotonergic neurotransmission in the central nervous system. MDD patients also experience alterations in cortisol and cytokines levels. Treatment with selective serotonin reuptake inhibitors (SSRIs) is the first-line antidepressant regimen for MDD. The aim of this study was to determine the effect of a combination of SSRIs and an immunomodulator-human dialyzable leukocyte extract (hDLE)-on cortisol and cytokines levels. Patients received SSRIs or SSRIs plus hDLE. The proinflammatory cytokines IL-1 β , IL-2, and IFN- γ ; anti-inflammatory cytokines IL-13 and IL-10; and 24-h urine cortisol were measured at weeks (W) 0, 5, 20, 36, and 52 of treatment. The reduction in cortisol levels in the SSRI-treated group was 30% until W52, in contrast, the combined treatment induced a 54% decrease at W36. The decline in cortisol in patients who were treated with SSRI plus hDLE correlated with reduction of anti-inflammatory cytokines and increases levels of proinflammatory cytokines at the study conclusion. These results suggest that the immune-stimulating activity of hDLE, in combination with SSRIs, restored the pro- and anti-inflammatory cytokine balance and cortisol levels in depressed patients versus those who were given SSRIs alone.

Monoamine neurocircuitry in depression and strategies for new treatments

Extensive studies showed that monoaminergic neurotransmission that involves serotonin (5-HT), norepinephrine (NE) and dopamine (DA) exerts major influence on brain circuits concerned by the regulation of mood, reactivity to psychological stress, self-control, motivation, drive, and cognitive performance. Antidepressants targeting monoamines directly affect the functional tone of these circuits, notably in limbic and frontocortical areas, and evidence has been provided that this action plays a key role in their therapeutic efficacy. Indeed, at least some of functional changes detected by functional magnetic resonance imaging in emotion- and cognitive-related circuits such as the one involving limbic-cortical-striatal-pallidal-thalamic connections in depressed patients can be reversed by monoamine-targeted antidepressants. However, antidepressants acting selectively on only one monoamine, such as selective inhibitors of 5-HT or NE reuptake, alleviate depression symptoms in a limited percentage of patients, and are poorly effective to prevent recurrence. Thorough investigations for the last 30 years allowed the demonstration of the existence of functional interactions between 5-HT, NE and DA systems, and the identification of the specific receptors involved. In particular, 5-HT systems were shown to exert negative influence on NE and DA systems through 5-HT2A and 5-HT2C receptor- mediated mechanisms, respectively. On the other hand, complex positive and negative influences of NE system on 5-HT neurotransmission are mediated through α1- and α2-adrenergic receptors, respectively. These data provided a rationale for the design of new, multimodal, therapeutic strategies involving drugs acting not only at the "historical" targets such as the 5-HT and/or the NE transporter, but also at other molecular targets to improve their efficacy and their tolerability.

Are BDNF and glucocorticoid activities calibrated?

One hypothesis to account for the onset and severity of neurological disorders is the loss of trophic support. Indeed, changes in the levels and activities of brain-derived neurotrophic factor (BDNF) occur in numerous neurodegenerative and neuropsychiatric diseases. A deficit promotes vulnerability whereas a gain of function facilitates recovery by enhancing survival, synapse formation and synaptic plasticity. Implementation of 'BDNF therapies', however, faces numerous methodological and pharmacokinetic issues. Identifying BDNF mimetics that activate the BDNF receptor or downstream targets of BDNF signaling represent an alternative approach. One mechanism that shows great promise is to study the interplay of BDNF and glucocorticoid hormones, a major class of natural steroid secreted during stress reactions and in synchrony with circadian rhythms. While small amounts of glucocorticoids support normal brain function, excess stimulation by these steroid hormones precipitates stress-related affective disorders. To date, however, because of the paucity of knowledge of underlying cellular mechanisms, deleterious effects of glucocorticoids are not prevented following extreme stress. In the present review, we will discuss the complementary roles shared by BDNF and glucocorticoids in synaptic plasticity, and delineate possible signaling mechanisms mediating these effects.

Glucocorticoid receptor and FKBP5 expression is altered following exposure to chronic stress: modulation by antidepressant treatment

Major depression is thought to originate from the interaction between susceptibility genes and adverse environmental events, in particular stress. The hypothalamus-pituitary-adrenal (HPA) axis is the major system involved in stress response and its dysregulation is an important element in the pathogenesis of depression. The stress response is therefore finely tuned through a series of mechanisms that control the trafficking of glucocorticoid receptors (GRs) to the nucleus, including binding to the chaperone protein FKBP5 and receptor phosphorylation, suggesting that these elements may also be affected under pathologic conditions. On these bases, we investigated FKBP5 and GR expression and phosphorylation in the hippocampus (ventral and dorsal) and in the prefrontal cortex of rats exposed to chronic mild stress (CMS) and we analyzed the effect of a concomitant antidepressant treatment. We found that animals exposed to CMS show increased expression of FKBP5 as well as enhanced cytoplasmic levels of GR, primarily in ventral hippocampus and prefrontal cortex. Chronic treatment with the antidepressant duloxetine is able to normalize such alterations, mainly in the prefrontal cortex. Moreover, we demonstrate that CMS-induced alterations of GR trafficking and transcription may be sustained by changes in receptor phosphorylation, which are also modulated by pharmacological intervention. In summary, while GR-related changes after CMS might be relevant for the depressive phenotype, the ability of antidepressant treatment to correct some of these alterations may contribute to the normalization of HPA axis dysfunctions associated with stress-related disorders.

Inhibition of P-glycoprotein enhances transport of imipramine across the blood-brain barrier: microdialysis studies in conscious freely moving rats

BACKGROUND AND PURPOSE

Recent studies indicate that efflux of antidepressants by the multidrug resistance transporter P-glycoprotein (P-gp) at the blood-brain barrier (BBB) may contribute to treatment-resistant depression (TRD) by limiting intracerebral antidepressant concentrations. In addition, clinical experience shows that adjunctive treatment with the P-gp inhibitor verapamil may improve the clinical outcome in TRD. Therefore, the present study aimed to investigate the effect of P-gp inhibition on the transport of the tricyclic antidepressant imipramine and its active metabolite desipramine across the BBB.

EXPERIMENTAL APPROACH

Intracerebral microdialysis in rats was used to monitor brain levels of imipramine and desipramine following i.v. imipramine administration, with or without pretreatment with one of the P-gp inhibitors verapamil or cyclosporin A (CsA). Plasma drug levels were also determined at regular intervals.

KEY RESULTS

Pretreatment with either verapamil or CsA resulted in significant increases in imipramine concentrations in the microdialysis samples, without altering imipramine plasma pharmacokinetics. Furthermore, pretreatment with verapamil, but not CsA, led to a significant elevation in plasma and brain levels of desipramine.

CONCLUSIONS AND IMPLICATIONS

The present study demonstrated that P-gp inhibition enhanced the intracerebral concentration of imipramine , thus supporting the hypothesis that P-gp activity restricts brain levels of certain antidepressants, including imipramine. These findings may help to explain reports of a beneficial response to adjunctive therapy with verapamil in TRD.

Neuroplasticity and major depression, the role of modern antidepressant drugs

The pathophysiology of depression has been traditionally attributed to a chemical imbalance and critical interactions between genetic and environmental risk factors, and antidepressant drugs suggested to act predominantly amplifying monoaminergic neurotransmission. This conceptualization may be currently considered reductive. The current literature about the pathophysiological mechanisms underlying depression, stress-related disorders and antidepressant treatment was examined. In order to provide a critical overview about neuroplasticity, depression and antidepressant drugs, a detailed Pubmed/Medline, Scopus, PsycLit, and PsycInfo search to identify all papers and book chapters during the period between 1980 and 2011 was performed. Pathological stress and depression determine relevant brain changes such as loss of dendritic spines and synapses, dendritic atrophy as well as reduction of glial cells (both in number and size) in specific areas such as the hippocampus and prefrontal cortex. An increased dendritic arborisation and synaptogenesis may instead be observed in the amygdala as a consequence of depression and stress-related disorders. While hippocampal and prefrontal functioning was impaired, amygdala functioning was abnormally amplified. Most of molecular abnormalities and biological changes of aberrant neuroplasticity may be explained by the action of glutamate. Antidepressant treatment is associated with neurogenesis, gliogenesis, dendritic arborisation, new synapse formation and cell survival both in the hippocampus and prefrontal cortex. Antidepressants (ADs) induce neuroplasticity mechanisms reversing the pathological effects of depression and stress-related disorders. The neuroplasticity hypothesis may explain the therapeutic and prophylactic action of ADs representing a new innovative approach to the pathophysiology of depression and stress-related disorders.

Central glucocorticoid receptor-mediated effects of the antidepressant, citalopram, in humans: a study using EEG and cognitive testing

Our previous work in cellular and animal models has shown that antidepressants activate glucocorticoid receptor (GR) translocation, induce GR down-regulation, and decrease GR-mediated effects in the presence of GR agonists. However, whether these effects can be extrapolated to the human brain is still unclear. In this study, the effects of four days of treatment with the antidepressant, citalopram (20 mg/day), or placebo, were assessed in a double-blind, placebo-controlled, cross-over study. Central GR-mediated effects were examined by the effects of a single dose of cortisol (30 mg, orally) on two measures known to be sensitive to glucocorticoid administration: EEG alpha power and working memory function. Twenty healthy male subjects aged between 18 and 33 years participated to the study. The results suggest that GR activation by antidepressants, and the subsequent decrease in GR-mediated effects in the presence of GR agonists, indeed occurs in the human brain. Specifically, pre-treatment with citalopram decreased the well-known ability of cortisol to increase EEG alpha power and to impair working memory: cortisol-induced increase in EEG alpha power was (anteriorly) +15 to +20% (p=0.01) after placebo and +5 to +8% (p>0.5) after citalopram; and cortisol-induced increase in working memory errors was (at level 12, on average) 2.50 vs. 4.55 (p<0.05) after placebo and 4.10 vs. 3.35 (p>0.05) after citalopram. No effects were detected on alerting. These results are consistent with the notion that citalopram treatment activates GR translocation and inhibits the functional consequences of the subsequent cortisol administration. Our study further emphasizes the importance of the GR as a target for antidepressant action in humans.

Dexamethasone stimulated gene expression in peripheral blood is a sensitive marker for glucocorticoid receptor resistance in depressed patients

Although gene expression profiles in peripheral blood in major depression are not likely to identify genes directly involved in the pathomechanism of affective disorders, they may serve as biomarkers for this disorder. As previous studies using baseline gene expression profiles have provided mixed results, our approach was to use an in vivo dexamethasone challenge test and to compare glucocorticoid receptor (GR)-mediated changes in gene expression between depressed patients and healthy controls. Whole genome gene expression data (baseline and following GR-stimulation with 1.5 mg dexamethasone p.o.) from two independent cohorts were analyzed to identify gene expression pattern that would predict case and control status using a training (N=18 cases/18 controls) and a test cohort (N=11/13). Dexamethasone led to reproducible regulation of 2670 genes in controls and 1151 transcripts in cases. Several genes, including FKBP5 and DUSP1, previously associated with the pathophysiology of major depression, were found to be reliable markers of GR-activation. Using random forest analyses for classification, GR-stimulated gene expression outperformed baseline gene expression as a classifier for case and control status with a correct classification of 79.1 vs 41.6% in the test cohort. GR-stimulated gene expression performed best in dexamethasone non-suppressor patients (88.7% correctly classified with 100% sensitivity), but also correctly classified 77.3% of the suppressor patients (76.7% sensitivity), when using a refined set of 19 genes. Our study suggests that in vivo stimulated gene expression in peripheral blood cells could be a promising molecular marker of altered GR-functioning, an important component of the underlying pathology, in patients suffering from depressive episodes.

Interactions between antidepressants and P-glycoprotein at the blood-brain barrier: clinical significance of in vitro and in vivo findings

The drug efflux pump P-glycoprotein (P-gp) plays an important role in the function of the blood-brain barrier by selectively extruding certain endogenous and exogenous molecules, thus limiting the ability of its substrates to reach the brain. Emerging evidence suggests that P-gp may restrict the uptake of several antidepressants into the brain, thus contributing to the poor success rate of current antidepressant therapies. Despite some inconsistency in the literature, clinical investigations of potential associations between functional single nucleotide polymorphisms in ABCB1, the gene which encodes P-gp, and antidepressant response have highlighted a potential link between P-gp function and treatment-resistant depression (TRD). Therefore, co-administration of P-gp inhibitors with antidepressants to patients who are refractory to antidepressant therapy may represent a novel therapeutic approach in the management of TRD. Furthermore, certain antidepressants inhibit P-gp in vitro, and it has been hypothesized that inhibition of P-gp by such antidepressant drugs may play a role in their therapeutic action. The present review summarizes the available in vitro, in vivo and clinical data pertaining to interactions between antidepressant drugs and P-gp, and discusses the potential relevance of these interactions in the treatment of depression.

A placebo-controlled study of sertraline's effect on cortisol response to the dexamethasone/corticotropin-releasing hormone test in healthy adults

RATIONALE

The dexamethasone/corticotropin-releasing hormone (Dex/CRH) test is a neuroendocrine probe involving serial blood sampling of cortisol during a standardized pharmacological challenge without inducing psychological distress in humans. Some past studies in depressed patients have shown a "normalization" or decrease in cortisol response to the Dex/CRH test following successful treatment with an antidepressant. Studies in nondepressed healthy adult samples have also shown aberrant cortisol reactivity to be associated with depression risk factors. These findings prompted research into the use of the Dex/CRH test as a tool for developing antidepressant drugs.

OBJECTIVES

In this study, the Dex/CRH test was evaluated with regard to its potential utility for drug development in nonclinical samples.

METHODS

The Dex/CRH test was administered before and after 6 weeks of blinded treatment with either sertraline 100 mg/day or matching placebo in 22 healthy adults (13 women, nine men).

RESULTS

Cortisol response to the Dex/CRH test increased following treatment with standard doses of sertraline, compared to placebo, after controlling for age and sex.

CONCLUSIONS

The observed pattern of change contrasts with results from published studies in depressed patients and with our initial hypothesis.

Desipramine treatment has minimal effects on the brain accumulation of glucocorticoids in P-gp-deficient and wild-type mice

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis in patients with depression can be reduced by antidepressants, which are thought to improve endogenous glucocorticoid-mediated negative feedback. A proportion of peripherally released glucocorticoids need to enter brain tissue, protected by the blood-brain barrier (BBB), in order to achieve this negative feedback effect at the level of the central nervous systems (CNS). The multidrug resistance transporter P-glycoprotein (P-gp) has been shown to actively transport glucocorticoid hormones and has been implicated in the regulation of glucocorticoid access to the CNS. Using an in situ brain/choroid plexus perfusion method, we tested the hypothesis that the antidepressant desipramine increases glucocorticoid accumulation in the mouse brain by inhibiting P-gp, following either chronic treatment (8 days, 20 mg/kg/day, IP) or acute administration (20 min brain perfusion in the presence of either 0.9 μM or 10 μM desipramine). Contrary to our hypothesis, chronic treatment with desipramine did not affect the accumulation of [³H]dexamethasone in any sample compared to saline-treated mice. Acute desipramine had limited and variable effects on glucocorticoid accumulation in the CNS, with accumulation of [³H]dexamethasone increased in the cerebellum, accumulation of [³H]cortisol reduced in the frontal cortex, hypothalamus, and cerebellum, and accumulation of [³H]corticosterone (the endogenous glucocorticoid in rodents) not affected. Overall, under the conditions tested, these results do not support the hypothesis that treatment with desipramine can inhibit P-gp at the BBB and subsequently increase the accumulation of glucocorticoids in the brain.

Antidepressants increase human hippocampal neurogenesis by activating the glucocorticoid receptor

Antidepressants increase adult hippocampal neurogenesis in animal models, but the underlying molecular mechanisms are unknown. In this study, we used human hippocampal progenitor cells to investigate the molecular pathways involved in the antidepressant-induced modulation of neurogenesis. Because our previous studies have shown that antidepressants regulate glucocorticoid receptor (GR) function, we specifically tested whether the GR may be involved in the effects of these drugs on neurogenesis. We found that treatment (for 3-10 days) with the antidepressant, sertraline, increased neuronal differentiation via a GR-dependent mechanism. Specifically, sertraline increased both immature, doublecortin (Dcx)-positive neuroblasts (+16%) and mature, microtubulin-associated protein-2 (MAP2)-positive neurons (+26%). This effect was abolished by the GR-antagonist, RU486. Interestingly, progenitor cell proliferation, as investigated by 5'-bromodeoxyuridine (BrdU) incorporation, was only increased when cells were co-treated with sertraline and the GR-agonist, dexamethasone, (+14%) an effect which was also abolished by RU486. Furthermore, the phosphodiesterase type 4 (PDE4)-inhibitor, rolipram, enhanced the effects of sertraline, whereas the protein kinase A (PKA)-inhibitor, H89, suppressed the effects of sertraline. Indeed, sertraline increased GR transactivation, modified GR phosphorylation and increased expression of the GR-regulated cyclin-dependent kinase-2 (CDK2) inhibitors, p27(Kip1) and p57(Kip2). In conclusion, our data suggest that the antidepressant, sertraline, increases human hippocampal neurogenesis via a GR-dependent mechanism that requires PKA signaling, GR phosphorylation and activation of a specific set of genes. Our data point toward an important role for the GR in the antidepressant-induced modulation of neurogenesis in humans.

The glucocorticoid receptor: pivot of depression and of antidepressant treatment?

Hyperactivity of the hypothalamus-pituitary-adrenal (HPA) axis and increased levels of glucocorticoid hormones in patients with depression have mostly been ascribed to impaired feedback regulation of the HPA axis, possibly caused by altered function of the receptor for glucocorticoid hormones, the glucocorticoid receptor (GR). Antidepressants, in turn, ameliorate many of the neurobiological disturbances in depression, including HPA axis hyperactivity, and thereby alleviate depressive symptoms. There is strong evidence for the notion that antidepressants exert these effects by modulating the GR. Such modulations, however, can be manifold and range from regulation of receptor expression to post-translational modifications, which may result in differences in GR nuclear translocation and GR-dependent gene transcription. The idea that the therapeutic action of antidepressants is mediated, at least in part, by restoring GR function, is consistent with studies showing that decreased GR function contributes to HPA axis hyperactivity and to the development of depressive symptoms. Conversely, excessive glucocorticoid signalling, which requires an active GR, is associated with functional impairments in the depressed brain, especially in the hippocampus, where it results in reduced neurogenesis and impaired neuroplasticity. In this review, we will focus on the GR as a key player in the precipitation, development and resolution of depression. We will discuss potential explanations for the apparent controversy between glucocorticoid resistance and the detrimental effects of excessive glucocorticoid signalling. We will review some of the evidence for modulation of the GR by antidepressants and we will provide further insight into how antidepressants may regulate the GR to overcome depressive symptoms.

The effects of antidepressants on mitochondrial function in a model cell system and isolated mitochondria

The in vitro effects of antidepressant drugs on mitochondrial function were investigated in a CHOβ(2)SPAP cell line used previously to determine the effects of antidepressants on gene transcription (Abdel-Razaq et al., Biochem Pharmacol 73:1995-2003, 2007) and in rat heart isolated mitochondria. Apoptotic effects of clomipramine (CLOM), desipramine (DMI) and of norfluoxetine (NORF, the active metabolite of fluoxetine), on cellular viability were indicated by morphological changes and concentration-dependent increases in caspase-3 activity in CHO cells after 18 h exposure to CLOM, DMI and NORF. However, tianeptine (TIAN) was without effect. CLOM and NORF both reduced integrated mitochondrial function as shown by marked reductions in membrane potential (MMP) in mitochondria isolated from rat hearts. DMI also showed a similar but smaller effect, whereas, TIAN did not elicit any significant change in MMP. Moreover, micromolar concentrations of CLOM, DMI and NORF caused significant inhibitions of the activities of mitochondrial complexes (I, II/III and IV). The inhibitory effects on complex IV activity were most marked. TIAN inhibited only complex I activity at concentrations in excess of 20 μM. The observed inhibitory effects of antidepressants on the mitochondrial complexes were accompanied by a significant decrease in the mitochondrial state-3 respiration at concentrations above 10 μM. The results demonstrate that the apoptotic cell death observed in antidepressant-treated cells could be due to disruption of mitochondrial function resulting from multiple inhibition of mitochondrial enzyme complexes. The possibility that antimitochondrial actions of antidepressants could provide a potentially protective pre-conditioning effect is discussed.

Central nervous system (CNS) delivery of glucocorticoids is fine-tuned by saturable transporters at the blood-CNS barriers and nonbarrier regions

Proper functioning of the hypothalamic-pituitary-adrenal axis depends on the ability of glucocorticoids (GCs), mainly cortisol in humans and corticosterone in rodents, to access brain targets and regulate their own secretion. Being highly lipophilic, GCs have been assumed to passively diffuse through the cell membrane. However, the access of these GCs to the brain may be a more complicated process, because the free movement of molecules into the central nervous system (CNS) is restricted by the presence of the blood-brain and blood-cerebrospinal fluid barriers. GCs do interact with some transporter systems, including the efflux transporter, P-glycoprotein, and members of the organic anion transporter polypeptide (oatp) family, both of which have been found at the blood-CNS barriers. Using an in situ brain/choroid plexus perfusion, P-glycoprotein was shown to not majorly regulate the access of [(3)H]cortisol and [(3)H]corticosterone to the choroid plexus or pituitary gland. Interactions of [(3)H]cortisol and [(3)H]corticosterone with saturable influx transporters were detected at the hypothalamus, cerebellum, choroid plexus, and pituitary gland. Oatp2 seems to have some role in the influx of [(3)H]cortisol and [(3)H]corticosterone to the choroid plexus and the pituitary gland and other transporters, unlikely to be oatp2, may play a very minor role in the access of [(3)H]cortisol and [(3)H]corticosterone to the brain, as well as having a significant effect on [(3)H]glucocorticoid receptor accumulation in the pituitary gland. Overall, these data suggest that the majority of cortisol and corticosterone present in the plasma diffuse into the CNS and that transporters do not play a major role in the accumulation of these GCs in the brain.

In vitro and in vivo evaluation of the effects of duloxetine on P-gp function

OBJECTIVE

To evaluate the effect of duloxetine (DLX) on the P-glycoprotein (P-gp) function in vitro and in vivo.

METHOD

In vitro experiment was conducted using the Caco-2 cell, a human colon cancer cell line that naturally expresses the P-gp and P-gp function was evaluated by monitoring whether DLX affect the accumulation of Rhd123. In vivo study was conducted by quantitating the effect of orally administered DLX on the bioavailability of talinolol.

RESULTS

In the in vitro study, incubation of Caco-2 cell with DLX caused a concentration-dependent increase in the accumulation of Rhd123. In the in vivo study, co-administration of DLX increased the bioavailability of talinolol. The ratio (90% confidence intervals) of AUC(0-60), AUC(0-∞), and C(max) (talinolol alone versus talinolol plus DLX) were 0.87(0.77-1.06), 0.85(0.74-1.01), 0.87 (0.68-1.12).

CONCLUSION

Our results suggest that DLX could inhibit the function of P-gp in vitro and in vivo, and caution should be exercised when DLX is to be co-administered with drugs that are P-gp substrate.

Housekeeping gene expression is affected by antidepressant treatment in a mouse fibroblast cell line

Quantitative real-time polymerase chain reaction (PCR) is an effective approach in investigating the effects of exogenous compounds on gene expression. This is often achieved by exploiting so-called 'housekeeping' genes as baseline controls to normalise expression levels, which have historically been assumed to have a relatively stable expression pattern. Recent non-in-vitro studies have questioned the validity of this, but previous in-vitro data were lacking following antidepressant treatment. We here investigated the stability of 12 housekeeping genes during treatment of the mouse L929 fibroblast cell line with escitalopram and nortriptyline. Cells were cultured in the presence of antidepressant at 1 microM or 10 microM for 30 min, 24 h or 48 h, and RNA subjected to quantitative PCR (qPCR). Stability of relative transcript expression values was assessed via gene-gene expression ratios and intra- and inter-group variation (using geNorm and NormFinder programs). The three most stable transcripts were adenosine triphosphate (ATP) synthase, H+ transporting mitochondrial F1 complex, beta subunit, beta-2 microglobulin and cytochrome c-1. The least stable were Gapdh, eukaryotic translation initiation factor 4A2 and Calnexin (Canx). In conclusion, care must be taken when choosing reference transcripts for analysis in qPCR. For in-vitro pharmacological studies, it should not be assumed that 'housekeeping' genes are stable.

Behavioural and neuroplastic effects of the new-generation antidepressant agomelatine compared to fluoxetine in glucocorticoid receptor-impaired mice

Major depression is associated with reduced hippocampal volume linked to stress and high glucocorticoid secretion. Glucocorticoid receptor-impaired (GR-i) mice, a transgenic model for affective disorders with hypothalamic-pituitary-adrenal (HPA) axis feedback control deficit, were used to assess the antidepressant-like effects of the mixed melatonin receptor agonist/5-HT(2C) receptor antagonist, agomelatine, compared to the selective 5-HT reuptake inhibitor (SSRI), fluoxetine, on hippocampal neurogenesis, GR and BDNF expression and antidepressant-responsive behaviour (tail suspension test, TST). GR-i and paired wild-type (WT) mice were given acute or chronic (21 d) treatment with these drugs. Both hippocampal cell proliferation and BDNF mRNA expression were down-regulated in GR-i mice, and these alterations were reversed by chronic agomelatine and fluoxetine treatments, whereas GR mRNA down-regulation was reversed only by agomelatine. Furthermore, chronic agomelatine, but not fluoxetine, increased survival of newly formed cells in the ventral part of the hippocampus without changing their phenotypic differentiation into neurons. In the TST, the enhanced immobility of GR-i mice was reduced to WT level by acute (but not chronic) fluoxetine and chronic (but not acute) agomelatine. These results indicate that agomelatine reversed the neuroplastic changes and helpless behaviour associated with HPA axis alterations in GR-i mice, suggesting neurobiological and behavioural effects mostly similar to those typically seen with classical antidepressants such as fluoxetine, but through clearly distinct mechanisms.

Antidepressants, but not antipsychotics, modulate GR function in human whole blood: an insight into molecular mechanisms

Clinical studies have demonstrated an impairment of glucocorticoid receptor (GR)-mediated negative feedback on the hypothalamic-pituitary-adrenal (HPA) axis in patients with major depression (GR resistance), and its resolution by antidepressant treatment. Recently, we showed that this impairment is indeed due to a dysfunction of GR in depressed patients (Carvalho et al., 2009), and that the ability of the antidepressant clomipramine to decrease GR function in peripheral blood cells is impaired in patients with major depression who are clinically resistant to treatment (Carvalho et al. 2008). To further investigate the effect of antidepressants on GR function in humans, we have compared the effect of the antidepressants clomipramine, amytriptiline, sertraline, paroxetine and venlafaxine, and of the antipsychotics, haloperidol and risperidone, on GR function in peripheral blood cells from healthy volunteers (n=33). GR function was measured by glucocorticoid inhibition of lypopolysaccharide (LPS)-stimulated interleukin-6 (IL-6) levels. Compared to vehicle-treated cells, all antidepressants inhibited dexamethasone (DEX, 10-100nM) inhibition of LPS-stimulated IL-6 levels (p values ranging from 0.007 to 0.1). This effect was specific to antidepressants, as antipsychotics had no effect on DEX-inhibition of LPS-stimulated IL-6 levels. The phosphodiesterase (PDE) type 4 inhibitor, rolipram, potentiated the effect of antidepressants on GR function, while the GR antagonist, RU-486, inhibited the effect of antidepressants on GR function. These findings indicate that the effect of antidepressants on GR function are specific for this class of psychotropic drugs, and involve second messenger pathways relevant to GR function and inflammation. Furthermore, it also points towards a possible mechanism by which one maybe able to overcome treatment-resistant depression. Research in this field will lead to new insights into the pathophysiology and treatment of affective disorders.

Xenobiotic, bile acid, and cholesterol transporters: function and regulation

Transporters influence the disposition of chemicals within the body by participating in absorption, distribution, and elimination. Transporters of the solute carrier family (SLC) comprise a variety of proteins, including organic cation transporters (OCT) 1 to 3, organic cation/carnitine transporters (OCTN) 1 to 3, organic anion transporters (OAT) 1 to 7, various organic anion transporting polypeptide isoforms, sodium taurocholate cotransporting polypeptide, apical sodium-dependent bile acid transporter, peptide transporters (PEPT) 1 and 2, concentrative nucleoside transporters (CNT) 1 to 3, equilibrative nucleoside transporter (ENT) 1 to 3, and multidrug and toxin extrusion transporters (MATE) 1 and 2, which mediate the uptake (except MATEs) of organic anions and cations as well as peptides and nucleosides. Efflux transporters of the ATP-binding cassette superfamily, such as ATP-binding cassette transporter A1 (ABCA1), multidrug resistance proteins (MDR) 1 and 2, bile salt export pump, multidrug resistance-associated proteins (MRP) 1 to 9, breast cancer resistance protein, and ATP-binding cassette subfamily G members 5 and 8, are responsible for the unidirectional export of endogenous and exogenous substances. Other efflux transporters [ATPase copper-transporting beta polypeptide (ATP7B) and ATPase class I type 8B member 1 (ATP8B1) as well as organic solute transporters (OST) alpha and beta] also play major roles in the transport of some endogenous chemicals across biological membranes. This review article provides a comprehensive overview of these transporters (both rodent and human) with regard to tissue distribution, subcellular localization, and substrate preferences. Because uptake and efflux transporters are expressed in multiple cell types, the roles of transporters in a variety of tissues, including the liver, kidneys, intestine, brain, heart, placenta, mammary glands, immune cells, and testes are discussed. Attention is also placed upon a variety of regulatory factors that influence transporter expression and function, including transcriptional activation and post-translational modifications as well as subcellular trafficking. Sex differences, ontogeny, and pharmacological and toxicological regulation of transporters are also addressed. Transporters are important transmembrane proteins that mediate the cellular entry and exit of a wide range of substrates throughout the body and thereby play important roles in human physiology, pharmacology, pathology, and toxicology.

Sexually dimorphic functional alterations of rat hepatic glucocorticoid receptor in response to fluoxetine

Gender-related differences in the expression and functional properties of the hepatic glucocorticoid receptor were studied before and after antidepressant fluoxetine administration to both unstressed and rats exposed to a chronic social isolation stress. Some of the receptor's functional properties, including hormone-binding capacity (B(max)), hormone-binding potency (B(max)/K(D) ratio) and the DNA-binding ability, were found to be sexually dimorphic. Fluoxetine treatment (5mg/kg body mass, 21day, intraperitoneally) induced a decrease in B(max) and in the amount of Hsp70 co-immunoprecipitated with the glucocorticoid receptor only in males, and stimulated the association of the receptor with Hsp90 in females. When applied during the last three weeks of the 6-week isolation, fluoxetine parallelly elevated B(max) and the receptor protein level in female animals, while in males diminished B(max) and inhibited association of the receptor with Hsp70. Binding of dexamethasone-receptor complexes both to DNA-cellulose and to isolated liver nuclei did not appear to be a target for fluoxetine action. The results point to sex-related differences in the glucocorticoid receptor functioning and in its response to fluoxetine, and suggest that these differences may contribute to well known sexual dimorphism in the sensitivity to stress, to stress-related disorders and to antidepressant treatment.

Risk factors for development of depression and psychosis. Glucocorticoid receptors and pituitary implications for treatment with antidepressant and glucocorticoids

Increased levels of glucocorticoid hormones-the main product of the hypothalamic-pituitary-adrenal (HPA) axis-have been considered to be "depressogenic," but this notion has largely derived from studies in patients with endocrine conditions, such as Cushing's syndrome or exogenous treatment with synthetic glucocorticoids. In these conditions, it is likely that the full impact of the high glucocorticoid levels is felt on the brain, through over-stimulation of the glucocorticoid receptors (GRs); indeed, normalizing these high levels leads to an improvement of mood in these patients. However, a completely different mechanism may be operating in major depression, where the increased levels of glucocorticoid hormones are conceptualized as driven by an impairment in GR function (glucocorticoid resistance), and therefore as a "compensatory" mechanism. Moreover, clinical and experimental studies have shown that antidepressants increase GR function, thus leading to resolution of glucocorticoid resistance. Interestingly, a number of studies have also demonstrated that manipulating GR function with both agonists and antagonists has an antidepressant effect, and indeed that other drugs targeting the HPA axis and cortisol secretion-even drugs with opposite effects on the HPA axis-have antidepressant effects. These studies do not support the notion that "high levels of glucocorticoids" always have a depressogenic effect, nor that decreasing the effects of these hormones always has an antidepressant effects.

Glucocorticoid dysregulations and their clinical correlates. From receptors to therapeutics

Clinicians have long known that a substantial proportion of patients treated with high-dose glucocorticoids experience a variety of serious side effects, including metabolic syndrome, bone loss, and mood shifts, such as depressive symptomatology, manic or hypomanic symptoms, and even suicide. The reason for individual variability in expression or severity of these side effects is not clear. However, recent emerging literature is beginning to shed light on possible mechanisms of these effects. As an introduction to this volume, this chapter will review the basic biology of glucocorticoid release and molecular mechanisms of glucocorticoid receptor function, and will discuss how dysregulation of glucocorticoid action at all levels could contribute to such side effects. At the molecular level, glucocorticoid receptor polymorphisms may be associated either with receptor hypofunction or hyperfunction and could thus contribute to differential individual sensitivity to the effects of glucocorticoid treatment. Numerous factors regulate hypothalamic-pituitary-adrenal (HPA) axis responsiveness, which could also contribute to individual differences in glucocorticoid side effects. One of these is sex hormone status and the influence of estrogen and progesterone on HPA axis function and mood. Another is immune system activity, in which immune molecules, such as interleukins and cytokines, activate the HPA axis and alter brain function, including memory, cognition, and mood. The effects of cytokines in inducing sickness behaviors, which overlap with depressive symptomatology, could also contribute to individual differences in such symptomatology. Taken together, this knowledge will have important relevance for identifying at-risk patients to avoid or minimize such side effects when they are treated with glucocorticoids. A framework for assessment of patients is proposed that incorporates functional, physiological, and molecular biomarkers to identify subgroups of patients at risk for depressive symptomatology associated with glucocorticoid treatment, and for prevention of side effects, which in many cases can be life-threatening.

A proteomic investigation of similarities between conventional and herbal antidepressant treatments

Increasing clinical evidence for the effectiveness of herbal antidepressants has led to investigations at the molecular level. Using two-dimensional gel electrophoresis, this study investigated similarities in protein expression between clomipramine, St John's wort and a Chinese herbal formula, xiao-yao-san, often used in mood disorder treatment. HT22 cells, derived from a mouse hippocampal cell line, were treated for 24 h, and protein expression was compared with that of the untreated cells (n = 4/group). Forty-three protein spots were found to be significantly differentially expressed (P < 0.05) in more than one of the treatment groups. Twenty-nine of these were identified using mass spectrometry. The most affected proteins were those involved in the cytoskeleton and energy metabolism, and an up-regulation of vimentin by all three treatments was confirmed by Western blotting. This study provides preliminary evidence for multiple common molecular targets between conventional and alternative antidepressants, which appear to collectively affect neuronal plasticity.

Characterization of a glucocorticoid receptor gene (GR, NR3C1) promoter polymorphism reveals functionality and extends a haplotype with putative clinical relevance

Hyperactivity of the hypothalamus-pituitary-adrenal (HPA) axis has been associated with the etiology of major depression. One of the factors underlying altered glucocorticoid signaling might be variability of the glucocorticoid receptor gene (GR, NR3C1). GR polymorphisms have been associated with variability in glucocorticoid sensitivity and endocrine responses to psychosocial stress. Furthermore, a common GR SNP (rs10482605), located in the promoter region, has been associated with major depression. We performed functional characterization of this SNP in vitro using a reporter gene assay under different stimulation conditions. Furthermore, we genotyped 219 subjects previously genotyped for four common GR SNPs to further characterize GR haplotype structure. The minor C allele of the rs10482605 SNP showed reduced transcriptional activity under unstimulated conditions and under different stimulation conditions in two brain derived cell lines. Linkage analyses revealed that the rs10482605 SNP is in high linkage disequilibrium with a A/G SNP in exon 9beta (rs6198), associated with relative glucocorticoid resistance and increased GRbeta mRNA stability. We provide evidence that two functional GR SNPs in linkage disequilibrium are responsible for both regulation of GR expression and mRNA stability. This newly characterized haplotype could increase the risk for the development of stress related disorders, including major depression.