Long-term antidepressant administration alters corticotropin-releasing hormone, tyrosine hydroxylase, and mineralocorticoid receptor gene expression in rat brain. Therapeutic implications

Neuroimmune modulation by tryptophan derivatives in neurological and inflammatory disorders

The nervous and immune systems are highly developed, and each performs specialized physiological functions. However, they work together, and their dysfunction is associated with various diseases. Specialized molecules, such as neurotransmitters, cytokines, and more general metabolites, are essential for the appropriate regulation of both systems. Tryptophan, an essential amino acid, is converted into functional molecules such as serotonin and kynurenine, both of which play important roles in the nervous and immune systems. The role of kynurenine metabolites in neurodegenerative and psychiatric diseases has recently received particular attention. Recently, we found that hyperactivity of the kynurenine pathway is a critical risk factor for septic shock. In this review, we first outline neuroimmune interactions and tryptophan derivatives and then summarized the changes in tryptophan metabolism in neurological disorders. Finally, we discuss the potential of tryptophan derivatives as therapeutic targets for neuroimmune disorders.

Anxiolytic effects of Chrysanthemum morifolium Ramat Carbonisata-based carbon dots in mCPP-induced anxiety-like behavior in mice: a nature-inspired approach

Introduction: Anxiety disorders have emerged as a predominant health concern, yet existing pharmacological treatments for anxiety still present various challenges. Chrysanthemum morifolium Ramat Carbonisata (CMRC) has been utilized in China for approximately 400 years as a therapeutic intervention for anxiety disorders. In this study, a novel type of carbon dots derived from the decoction of Chrysanthemum morifolium Ramat Carbonisata (CMRC-CDs) was identified and isolated, and their morphological structure and functional groups were characterized. Furthermore, the effects of CMRC-CDs on m-chlorophenylpiperazine (mCPP)-induced anxiety-like behaviour in mice were examined and quantified. In order to investigate the potential mechanisms of their anxiolytic effects, concentrations of hypothalamic-pituitary-adrenal (HPA) axis hormones, amino acid neurotransmitters, and monoamine neurotransmitters were measured. Methods: In this study, we synthesized CMRC-CDs and evaluated their potential anti-anxiety effects in a controlled experiment involving 48 male ICR mice. The mice were randomly divided into six groups, treated with CMRC-CDs at different doses for 14 days, and subjected to Open-Field (OF) and Elevated Plus Maze (EPM) tests. Post-behavioral evaluations, blood samples and brain tissues were collected for neurotransmitter and Hypothalamic-Pituitary-Adrenal (HPA) axis hormone quantification via ELISA. Additionally, cytotoxicity of CMRC-CDs was assessed using a Cell Counting Kit-8 (CCK-8) assay on RAW 264.7 cells. Results and Discussion: CMRC-CDs were spherical and homogeneously dispersed, with diameters ranging from 1.4 to 4.0 nm and an abundance of chemical groups on their surface. In the open-field (OF) test, mice pre-treated with CMRC-CDs demonstrated an increased proportion of time spent in the central area and a higher frequency of entries into the central area. In the elevated plus maze (EPM) test, mice pre-treated with CMRC-CDs exhibited a greater number of entries into the open arm and an extended duration spent in the open arm. CMRC-CDs were observed to decrease serum concentrations of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and corticosterone (CORT). Furthermore, CMRC-CDs were found to increase γ-aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) levels, while concurrently reducing glutamic acid (Glu) concentrations in brain tissue. CMRC-CDs demonstrated anxiolytic effects, which may be attributed to their modulation of hormones and neurotransmitters. This finding suggests the potential therapeutic value of CMRC-CDs in the clinical treatment of anxiety disorders.

Clinical Ageing

Ageing is generally characterised by the declining ability to respond to stress, increasing homeostatic imbalance, and increased risk of ageing-associated diseases . Mechanistically, the lifelong accumulation of a wide range of molecular and cellular impairments leads to organismal senescence. The aging population poses a severe medical concern due to the burden it places on healthcare systems and the general public as well as the prevalence of diseases and impairments associated with old age. In this chapter, we discuss organ failure during ageing as well as ageing of the hypothalamic-pituitary-adrenal axis and drugs that can regulate it. A much-debated subject is about ageing and regeneration. With age, there is a gradual decline in the regenerative properties of most tissues. The goal of regenerative medicine is to restore cells, tissues, and structures that are lost or damaged after disease, injury, or ageing. The question arises as to whether this is due to the intrinsic ageing of stem cells or, rather, to the impairment of stem-cell function in the aged tissue environment. The risk of having a stroke event doubles each decade after the age of 55. Therefore, it is of great interest to develop neurorestorative therapies for stroke which occurs mostly in elderly people. Initial enthusiasm for stimulating restorative processes in the ischaemic brain with cell-based therapies has meanwhile converted into a more balanced view, recognising impediments related to survival, migration, differentiation, and integration of therapeutic cells in the hostile aged brain environment. Therefore, a current lack of understanding of the fate of transplanted cells means that the safety of cell therapy in stroke patients is still unproven. Another issue associated with ischaemic stroke is that patients at risk for these sequels of stroke are not duly diagnosed and treated due to the lack of reliable biomarkers. However, recently neurovascular unit-derived exosomes in response to Stroke and released into serum are new plasma genetic and proteomic biomarkers associated with ischaemic stroke. The second valid option, which is also more economical, is to invest in prevention.

Routinely accessible parameters of mineralocorticoid receptor function, depression subtypes and response prediction: a post-hoc analysis from the early medication change trial in major depressive disorder

OBJECTIVES

Previous studies indicated a relationship between aldosterone, the mineralocorticoid receptor (MR), and antidepressant treatment outcome. Physiological indicators of MR function (blood pressure and electrolytes) are easily accessible and may therefore serve as useful predictors. Thus, our aim was to investigate the predictive value of peripheral MR-related markers for antidepressant treatment outcomes.

METHODS

826 MDD patients who had participated in the randomised-controlled Early Medication Change (EMC) trial were analysed. Depression severity and MR-related markers were assessed weekly. In 562 patients, genetic variation of five MR-related genes was determined.

RESULTS

Patients with blood pressure <120mmHg showed higher depression severity (p = 0.005) than patients with blood pressure ≥120mmHg. Patients with a melancholic subtype had significantly lower blood pressures (p = 0.004). Na⁺/K⁺ ratio was positively and K⁺-concentration was negatively correlated to depression severity and to relative changes in HAMD from baseline to day 14, and 56 respectively (p < 0.001). For none of the MR-related genes, genetic variation was associated with treatment outcomes.

CONCLUSIONS

We confirmed early observations of an altered peripheral MR sensitivity, reflected by lower blood pressure, low K⁺ or high Na⁺/K⁺ ratio in patients with more severe depression. These routinely collected biomarkers may potentially be useful for risk stratification in an early stage of treatment. Trial Registration: clinicaltrials.gov Identifier: NCT00974155; https://www.clinicaltrials.gov/ct2/results?term=NCT00974155.

Increased Levels of Cortisol in Individuals With Suicide Attempt and Its Relation With the Number of Suicide Attempts and Depression

BACKGROUND

Abnormalities in the hypothalamic-pituitary-adrenal axis (HPA) have been reported in individuals with suicide behavior. The aim of the study was to evaluate cortisol levels in peripheral plasma of individuals with more than one suicide attempt.

METHODS

Cortisol concentrations in peripheral plasma were measured using the ELISA technique. Suicide attempts were evaluated by the Columbia Suicide Severity Rating Scale, while depression was evaluated by the Hamilton Depression Rating Scale.

RESULTS

We found elevated cortisol levels in the suicide attempt group when compared with healthy controls (F = 7.26, p-value = 0.008), but no statistical differences with the psychiatric diseases group (F = 1.49, p-value = 0.22). Cortisol levels were higher in individuals with depression (F = 8.99, P = 0.004) and in individuals with two or more suicide attempts (F = 13.56, P < 0.001).

CONCLUSIONS

Cortisol levels are increased in individuals who attempt suicide and higher of cortisol concentrations in plasma regard to depression and more attempts of suicide.

Fluoxetine treatment supports predictive validity of the three hit model of depression in male PACAP heterozygous mice and underpins the impact of early life adversity on therapeutic efficacy

According to the three hit concept of depression, interaction of genetic predisposition altered epigenetic programming and environmental stress factors contribute to the disease. Earlier we demonstrated the construct and face validity of our three hit concept-based mouse model. In the present work, we aimed to examine the predictive validity of our model, the third willnerian criterion. Fluoxetine treatment was applied in chronic variable mild stress (CVMS)-exposed (environmental hit) CD1 mice carrying one mutated allele of pituitary adenylate cyclase-activating polypeptide gene (genetic hit) that were previously exposed to maternal deprivation (epigenetic hit) vs. controls. Fluoxetine reduced the anxiety level in CVMS-exposed mice in marble burying test, and decreased the depression level in tail suspension test if mice were not deprived maternally. History of maternal deprivation caused fundamental functional-morphological changes in response to CVMS and fluoxetine treatment in the corticotropin-releasing hormone-producing cells of the bed nucleus of the stria terminalis and central amygdala, in tyrosine-hydroxylase content of ventral tegmental area, in urocortin 1-expressing cells of the centrally projecting Edinger-Westphal nucleus, and serotonergic cells of the dorsal raphe nucleus. The epigenetic background of alterations was approved by altered acetylation of histone H3. Our findings further support the validity of both the three hit concept and that of our animal model. Reversal of behavioral and functional-morphological anomalies by fluoxetine treatment supports the predictive validity of the model. This study highlights that early life stress does not only interact with the genetic and environmental factors, but has strong influence also on therapeutic efficacy.

The PPARg System in Major Depression: Pathophysiologic and Therapeutic Implications

To an exceptional degree, and through multiple mechanisms, the PPARg system rapidly senses cellular stress, and functions in the CNS in glial cells, neurons, and cerebrovascular endothelial cell in multiple anti-inflammatory and neuroprotective ways. We now know that depression is associated with neurodegeneration in the subgenual prefrontal cortex and hippocampus, decreased neuroplasticity, and defective neurogenesis. Brain-derived neurotrophic factor (BDNF) is markedly depleted in these areas, and is thought to contribute to the neurodegeneration of the subgenual prefrontal cortex and the hippocampus. The PPARg system strongly increases BDNF levels and activity in these brain areas. The PPARg system promotes both neuroplasticity and neurogenesis, both via effects on BDNF, and through other mechanisms. Ample evidence exists that these brain areas transduce many of the cardinal features of depression, directly or through their projections to sites such as the amygdala and nucleus accumbens. Behaviorally, these include feelings of worthlessness, anxiety, dread of the future, and significant reductions in the capacity to anticipate and experience pleasure. Physiologically, these include activation of the CRH and noradrenergic system in brain and the sympathetic nervous system and hypothalamic-pituitary-adrenal axis in the periphery. Patients with depression are also insulin-resistant. The PPARg system influences each of these behavioral and physiological in ways that would ameliorate the manifestations of depressive illness. In addition to the cognitive and behavioral manifestations of depression, depressive illness is associated with the premature onsets of coronary artery disease, stroke, diabetes, and osteoporosis. As a consequence, patients with depressive illness lose approximately seven years of life. Inflammation and insulin resistance are two of the predominant processes that set into motion these somatic manifestations. PPARg agonists significantly ameliorate both pathological processes. In summary, PPARg augmentation can impact positively on multiple significant pathological processes in depression. These include loss of brain tissue, defective neuroplasticity and neurogenesis, widespread inflammation in the central nervous system and periphery, and insulin resistance. Thus, PPARg agonists could potentially have significant antidepressant effects.

Distinct regulation of hippocampal neuroplasticity and ciliary genes by corticosteroid receptors

Glucocorticoid hormones (GCs) — acting through hippocampal mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) — are critical to physiological regulation and behavioural adaptation. We conducted genome-wide MR and GR ChIP-seq and Ribo-Zero RNA-seq studies on rat hippocampus to elucidate MR- and GR-regulated genes under circadian variation or acute stress. In a subset of genes, these physiological conditions resulted in enhanced MR and/or GR binding to DNA sequences and associated transcriptional changes. Binding of MR at a substantial number of sites however remained unchanged. MR and GR binding occur at overlapping as well as distinct loci. Moreover, although the GC response element (GRE) was the predominant motif, the transcription factor recognition site composition within MR and GR binding peaks show marked differences. Pathway analysis uncovered that MR and GR regulate a substantial number of genes involved in synaptic/neuro-plasticity, cell morphology and development, behavior, and neuropsychiatric disorders. We find that MR, not GR, is the predominant receptor binding to >50 ciliary genes; and that MR function is linked to neuronal differentiation and ciliogenesis in human fetal neuronal progenitor cells. These results show that hippocampal MRs and GRs constitutively and dynamically regulate genomic activities underpinning neuronal plasticity and behavioral adaptation to changing environments.

Glucocorticoid hormones (GCs) are of critical importance for maintaining brain health, but their involvement in mental disorders is poorly understood. Here the authors show how GCs act through hippocampal mineralocorticoid and glucocorticoid receptors to impact the gene regulatory programs underpinning neuronal plasticity, ciliogenesis and behavioral adaptation.

The Neurocircuitry of Posttraumatic Stress Disorder and Major Depression: Insights Into Overlapping and Distinct Circuit Dysfunction-A Tribute to Ron Duman

The neurocircuitry that contributes to the pathophysiology of posttraumatic stress disorder and major depressive disorder, psychiatric conditions that exhibit a high degree of comorbidity, likely involves both overlapping and unique structural and functional changes within multiple limbic brain regions. In this review, we discuss neurobiological alterations that are associated with posttraumatic stress disorder and major depressive disorder and highlight both similarities and differences that may exist between these disorders to argue for the existence of a shared neurobiology. We highlight the key contributions based on preclinical studies, emerging from the late Professor Ronald Duman's research, that have shaped our understanding of the neurocircuitry that contributes to both the etiopathology and treatment of major depressive disorder and posttraumatic stress disorder.

Stereoisomeric selectivity in the endocrine-disrupting potential of cypermethrin using in vitro, in vivo, and in silico assays

Despite the ubiquity of cypermethrin (CYP) stereoisomers in environment biota, the stereoisomeric selectivity of endocrine-disrupting potency of α-CYP, β-CYP, and θ-CYP has not been well studied. In this study, dual-luciferase reporter gene assays were adopted to analyze their potential endocrine-disrupting effects via four receptors (ERα, GRα, MR and RXR). The results showed that α-CYP was antagonistic to ERα, GRα, and MR with RIC₂₀ of 9.1 × 10^-7, 7.6 × 10^-7, and 1.0 × 10^-6 M, respectively. β-CYP exhibited only ERα-mediated agonistic activity with a REC₂₀ of 2.1 × 10^-6 M. None of the CYP stereoisomers interacted with RXR. Molecular docking indicated that α-CYP had the strongest binding capacity to GRα among the compounds. The expression levels of steroid hormone-related genes in human adrenocortical carcinoma (H295R) cells displayed that all three compounds inhibited the transcription of 3-βHSD, indicating the block of turning cholesterol into different hormones. Both α-CYP and β-CYP upregulated genes encoding estrogen- and aldosterone-forming enzymes including 17-βHSD, CYP19, STAR, and CYP11B2. Mortality and malformation toxicity assays in zebrafish embryos revealed that the order of toxicity was α-CYP > β-CYP > θ-CYP. Our results indicated that α-CYP may pose the strongest endocrine-disrupting effects. The data provided here will be helpful to systematically understand stereoisomeric selectivity in the endocrine-disrupting effects of cypermethrin.

Endocrine Factors in Key Structural and Intracellular Changes in Depression

Endocrine disturbances play predominant roles in recently discovered, clinically relevant abnormalities in depression. These affect multiple sites in the prefrontal cortex, amygdala, hippocampus, nucleus accumbens, and habenula. Deficits consist of changes in volume, neuroplasticity, neural connectivity, synapse composition, and neurogenesis. Depression is associated with endocrine-related, premature systemic disease, that results in a loss of approximately 7 years of life. CRH, glucocorticoids, somatostatin, gonadal steroids, and thyroid hormones all contribute to the deficits that largely define the pathophysiologic presentation of depression. The World Health Organization ranks depression as the second greatest cause of disability worldwide. The response rate to current antidepressants is below 60%. It is important that new knowledge about the endocrine-mediated pathophysiology of depression be communicated to provide targets for new agents.

Pharmacological Treatment of Anxiety Disorders: The Role of the HPA Axis

Stress in general, and early life stress in particular, has been associated with the development of anxiety and mood disorders. The molecular, biological and psychological links between stress exposure and the pathogenesis of anxiety and mood disorders have been extensively studied, resulting in the search of novel psychopharmacological strategies aimed at targets of the hypothalamic-pituitary-adrenal (HPA) axis. Hyperactivity of the HPA axis has been observed in certain subgroups of patients with anxiety and mood disorders. In addition, the effects of different anti-anxiety agents on various components of the HPA axis has been investigated, including benzodiazepines, tricyclic antidepressants (TCAs), and selective serotonin reuptake inhibitors (SSRIs). For example, benzodiazepines, including clonazepam and alprazolam, have been demonstrated to reduce the activity of corticotrophin releasing factor (CRF) neurons in the hypothalamus. TCAs and SSRIs are also effective anti-anxiety agents and these may act, in part, by modulating the HPA axis. In this regard, the SSRI escitalopram inhibits CRF release in the central nucleus of the amygdala, while increasing glucocorticoid receptor (GRs) density in the hippocampus and hypothalamus. The molecular effects of these anti-anxiety agents in the regulation of the HPA axis, taken together with their clinical efficacy, may provide further understanding about the role of the HPA axis in the pathophysiology of mood and anxiety disorders, paving the way for the development of novel therapeutic strategies.

Markers of mineralocorticoid receptor function: changes over time and relationship to response in patients with major depression

The renin-angiotensin-aldosterone system and its hormone receptors, i.e. the angiotensin and mineralocorticoid receptor (MR), have emerged as important targets for central nervous system disorders and in particular for major depression. We have recently characterized baseline MR function as a predictor for treatment outcome with standard antidepressants. The aims of this study are (i) to characterize how strongly an early biomarker change (after 2 weeks) is related to outcome and (ii) whether these biomarker changes are related to the final outcome, that is, could serve as surrogate markers for response. Twenty-four of 30 patients with unipolar major depression completed the observational trial. MR-related biomarkers were assessed at baseline, 2 weeks, and 6 weeks of standard antidepressant treatment. These biomarkers included slow wave sleep (SWS), salivary cortisol and aldosterone after awakening, heart rate variability measured as respiratory sinus arrhythmia (RSA), systolic blood pressure, salt taste intensity (STI), salt pleasantness (SP), and plasma electrolytes. The Hamilton depression rating scale with 21 items was primarily used to determine depression severity. In the overall sample, STI increased and SP decreased significantly with treatment without a clear relationship with treatment outcome. No other significant changes were observed. Reductions in cortisol and aldosterone after 2 weeks of treatment were significantly related to improvement after 6 weeks (P<0.05). SWS increase after 2 and 6 weeks was by trend (P<0.08) correlated to clinical improvement after 6 weeks. Systolic blood pressure differentiated responders and nonresponders at baseline (P<0.05), but did not change significantly during treatment. We earlier identified a relationship between clinical outcome and baseline values of STI, SP, and RSA only in male patients; therefore, changes in this subgroup were analyzed separately: in male treatment responders, a trend toward an increase in SWS occurred after 2 (P<0.07) and 6 (P<0.07) weeks. Further, a trend toward RSA reduction (P<0.07) was observed. Changes in STI and SP were similar to the total group, but did not reach levels of significance. Early changes in central MR-related biomarkers appear to influence the outcome of standard antidepressant treatment: reduced salivary cortisol, increased SWS, and reduced RSA are linked to a better treatment outcome. These features point to a mechanism involving increased central MR activation in responders to standard antidepressants, but not in nonresponders.

Sex differences in hippocampal mineralocorticoid and glucocorticoid receptor mRNA expression in response to acute mate pair separation in zebra finches (Taeniopygia guttata)

Mate separation has been shown to mediate changes in physiological and behavioral processes via activation of the hypothalamo-pituitary-adrenal (HPA) axis in both mammalian and avian species. To elucidate the neural mechanisms associated with changes in the HPA axis in response to social stress, we investigated the effects of mate pair separation on circulating corticosterone concentrations as well as gene expression levels of mineralocorticoid receptor (MR), glucocorticoid receptor (GR), and corticotropin releasing hormone (CRH) in the hypothalamus and hippocampus of both male and female zebra finches, a species that forms strong pair bonds. Zebra finches (Taeniopygia guttata) were housed three to a cage (a mated pair plus a stimulus female), and were assigned to one of three new housing treatment groups: (1) male or female removed from their respective mate and placed in a cage with a new opposite sex conspecific and stimulus female (2) male or female that remained with their mate, but a new stimulus female was introduced, or (3) the subjects were handled but not separated from their mate or the stimulus female. After 48 hr in the new housing condition, we observed significant increases in plasma corticosterone concentrations in response to both mate pair and stimulus female separation. No significant differences in MR, GR, or CRH mRNA expression in the hypothalamus were observed in response to any treatment for both males and females. Females exhibited a significant up regulation in hippocampal MR, but not GR mRNA, whereas males exhibited a significant down regulation of both hippocampal MR and GR mRNA in response to mate pair separation. Thus, the hippocampus appears to play a key role in regulating sex specific responses to social stressors.

Research on potential biomarker correlates for suicidal behavior: A review

Suicide is a world health priority. Studies over the last few decades have revealed the complexity underlying the neurobiological mechanisms of suicide. Researchers have found dysregulations in the serotonergic system, the stress system, neural plasticity, lipid metabolism, and cell signaling pathways in relation to suicidal behaviors. These findings have provided more insight into the final path leading to suicide, at which medical intervention should be applied to prevent the action. However, because these molecular mechanisms have been implicated in both depression and suicide, the specificity of the mechanisms has been obscured. In this review, we summarize the main findings of studies on molecular mechanisms of suicidal behavior from the last 2 decades, with particular emphasis on the potential, independent role of each mechanism that is not contingent upon an underlying psychopathology, such as depression. The act of suicide is multifactorial; no single molecular mechanism is sufficient to fully account for the act. Knowledge of the reciprocal interactions among these molecular mechanisms and studying them in the context of brain circuitry by using neuroimaging techniques will provide a better understanding of the neurobiology of suicide.

Differential effects of imipramine and CORT118335 (Glucocorticoid receptor modulator/mineralocorticoid receptor antagonist) on brain-endocrine stress responses and depression-like behavior in female rats

Depression is commonly associated with hypothalamic-pituitary adrenal (HPA) axis dysfunction that primarily manifests as aberrant glucocorticoid secretion. Glucocorticoids act on Type I mineralocorticoid (MR) and Type II glucocorticoid receptors (GR) to modulate mood and endocrine responses. Successful antidepressant treatment normalizes HPA axis function, in part due to modulatory effects on MR and GR in cortico-limbic structures. Although women are twice as likely to suffer from depression, little is known about how antidepressants modulate brain, endocrine, and behavioral stress responses in females. Here, we assessed the impact of CORT118335 (GR modulator/MR antagonist) and imipramine (tricyclic antidepressant) on neuroendocrine and behavioral responses to restraint or forced swim stress (FST) in female rats (n=10-12/group). Increased immobility CORT118335 in the FST is purported to reflect passive coping or depression-like behavior. CORT118335 dampened adrenocorticotropic hormone (ACTH) and corticosterone responses to the FST, but did not affect immobility. Imipramine suppressed ACTH, but had minimal effects on corticosterone responses to FST. Despite these marginal effects, imipramine decreased immobility, suggesting antidepressant efficacy. In an effort to link brain-endocrine responses with behavior, c-Fos was assessed in HPA axis and mood modulatory regions in response to the FST. CORT118335 upregulated c-Fos expression in the paraventricular nucleus of the hypothalamus. Imipramine decreased c-Fos in the basolateral amygdala and hippocampus (CA1 and CA3), but increased c-Fos in the central amygdala. These data suggest the antidepressant-like (e.g., active coping) properties of imipramine may be due to widespread effects on cortico-limbic circuits that regulate emotional and cognitive processes.

A mixed glucocorticoid/mineralocorticoid receptor modulator dampens endocrine and hippocampal stress responsivity in male rats

Aberrant glucocorticoid secretion is implicated in the pathophysiology of stress-related disorders (i.e., depression, anxiety). Glucocorticoids exert biological effects via mineralocorticoid (MR) and glucocorticoid (GR) receptors. Previous data from our laboratory indicate that GR antagonism/modulation (i.e., mifepristone, CORT 108297) regulate endocrine, behavioral, and central stress responses. Because of the dynamic interplay between MR and GR on HPA axis regulation and emotionality, compounds targeting both receptors are of interest for stress-related pathology. We investigated the effects of CORT 118335 (a dual selective GR modulator/MR antagonist) on endocrine, behavioral, and central (c-Fos) stress responses in male rats. Rats were treated for five days with CORT 118335, imipramine (positive control), or vehicle and exposed to restraint or forced swim stress (FST). CORT 118335 dampened corticosterone responses to both stressors, without a concomitant antidepressant-like effect in the FST. Imipramine decreased corticosterone responses to restraint stress; however, the antidepressant-like effect of imipramine in the FST was independent of circulating glucocorticoids. These findings indicate dissociation between endocrine and behavioral stress responses in the FST. CORT 118335 decreased c-Fos expression only in the CA1 division of the hippocampus. Imipramine decreased c-Fos expression in the basolateral amygdala and CA1 and CA3 divisions of the hippocampus. Overall, the data indicate differential effects of CORT 118335 and imipramine on stress-induced neuronal activity in various brain regions. The data also highlight a complex relationship between neuronal activation in stress and mood regulatory brain regions and the ensuing impact on endocrine and behavioral stress responses.

NPY1 Receptor Agonist Modulates Development of Depressive-Like Behavior and Gene Expression in Hypothalamus in SPS Rodent PTSD Model

Delivery of neuropeptide Y (NPY) to the brain by intranasal infusion soon after traumatic stress has shown therapeutic potential, and prevented development of many behavioral and neuroendocrine impairments in the single prolonged stress (SPS) animal model of PTSD. Therefore, we examined whether the Y1R preferring agonist [Leu³¹Pro³⁴]NPY is sufficient to prevent development of SPS induced depressive-like behavioral changes, and hypothalamic gene expression as obtained with intranasal NPY intervention. Male Sprague-Dawely rats were given intranasal infusion of either NPY (150 μg/rat), a low (68 μg /rat), or high (132 μg/rat) dose of [Leu³¹Pro³⁴]NPY or vehicle immediately following the last SPS stressor, left undisturbed for 1 week and then tested for depressive-like behavior together with naïve unstressed controls. Vehicle treated animals had elevated immobility forced swim test (FST) and reduced sucrose preference, which were not observed in animals given NPY or the higher dose of [Leu³¹Pro³⁴]NPY. This dose of [Leu³¹Pro³⁴]NPY, like NPY, also prevented the SPS-elicited induction of CRF mRNA in the mediobasal hypothalamus. However, [Leu³¹Pro³⁴]NPY did not prevent, but rather enhanced, the SPS-triggered induction of GR and FKBP5 mRNA levels in the mediobasal hypothalamus. Thus, [Leu³¹Pro³⁴]NPY may be as effective as NPY and displays therapeutic potential for preventing development of depressive-like behaviors and dysregulation of the CRF/HPA system in PTSD. However, due to its different effects compared to NPY on GR and FKBP5 a broader agonist, such as NPY, may be more desirable.

Alterations in the corticotropin-releasing hormone (CRH) neurocircuitry: Insights into post stroke functional impairments

Although it is well accepted that changes in the regulation of the hypothalamic-pituitary adrenal (HPA) axis may increase susceptibility to affective disorders in the general population, this link has been less examined in stroke patients. Yet, the bidirectional association between depression and cardiovascular disease is strong, and stress increases vulnerability to stroke. Corticotropin-releasing hormone (CRH) is the central stress hormone of the HPA axis pathway and acts by binding to CRH receptors (CRHR) 1 and 2, which are located in several stress-related brain regions. Evidence from clinical and animal studies suggests a role for CRH in the neurobiological basis of depression and ischemic brain injury. Given its importance in the regulation of the neuroendocrine, autonomic, and behavioral correlates of adaptation and maladaptation to stress, CRH is likely associated in the pathophysiology of post stroke emotional impairments. The goals of this review article are to examine the clinical and experimental data describing (1) that CRH regulates the molecular signaling brain circuit underlying anxiety- and depression-like behaviors, (2) the influence of CRH and other stress markers in the pathophysiology of post stroke emotional and cognitive impairments, and (3) context and site specific interactions of CRH and BDNF as a basis for the development of novel therapeutic targets. This review addresses how the production and release of the neuropeptide CRH within the various regions of the mesocorticolimbic system influences emotional and cognitive behaviors with a look into its role in psychiatric disorders post stroke.

Reduced vasopressin receptors activation mediates the anti-depressant effects of fluoxetine and venlafaxine in bulbectomy model of depression

RATIONALE

In response to stress, corticotropin releasing hormone (CRH) and vasopressin (AVP) are released from the hypothalamus, activate their receptors (CRHR1, CRHR2 or AVPr1b), and synergistically act to induce adrenocorticotropic hormone (ACTH) release from the anterior pituitary. Overstimulation of this system has been frequently associated with major depression states.

OBJECTIVE

The objective of the study is to assess the role of AVP and CRH receptors in fluoxetine and venlafaxine effects on the expression of depression-related behavior.

METHODS

In an animal model of depression (olfactory bulbectomy in mice, OB), we evaluated the effects of fluoxetine or venlafaxine (both 10 mg/kg/day) chronic administration on depression-related behavior in the tail suspension test. Plasma levels of AVP, CRH, and ACTH were determined as well as participation of their receptors in the expression of depression related-behavior and gene expression of AVP and CRH receptors (AVPr1b, CRHR1, and CRHR2) in the pituitary gland.

RESULTS

The expression of depressive-like behavior in OB animals was reversed by treatment with both antidepressants. Surprisingly, OB-saline mice exhibited increased AVP and ACTH plasma levels, with no alterations in CRH levels when compared to sham mice. Chronic fluoxetine or venlafaxine reversed these effects. In addition, a significant increase only in AVPr1b gene expression was found in OB-saline.

CONCLUSION

The antidepressant therapy used seems to be more likely related to a reduced activation of AVP rather than CRH receptors, since a positive correlation between AVP levels and depressive-like behavior was observed in OB animals. Furthermore, a full restoration of depressive behavior was observed in OB-fluoxetine- or venlafaxine-treated mice only when AVP was centrally administered but not CRH.

The Role of Fludrocortisone in Cognition and Mood in Patients with Primary Adrenal Insufficiency (Addison's Disease)

BACKGROUND

Primary adrenal insufficiency (AI) requires hormone replacement therapy with fludrocortisone and hydrocortisone stimulating glucocorticoid (GR) and mineralocorticoid receptors (MR). Evidence from animal and human studies shows that MR function is crucial for cognitive function and mood. Regarding patients with AI, very little is known about the role of MR in cognitive function and mood.

METHODS

A repeated-measures within-subject design was used to determine whether cognitive function and mood are related to MR occupation in patients with AI. Intraindividually, patients were examined twice, with 1 week between testing days: once with fludrocortisone (high MR occupation) and once without fludrocortisone (low MR occupation). All patients kept their stable regimen of hydrocortisone. The assessment of cognitive function included executive function, attention, and verbal, visuospatial and working memory. Additionally, mood and blood pressure were measured.

RESULTS

Verbal memory improved significantly during high MR occupation (after fludrocortisone intake) compared to low MR occupation [without fludrocortisone, t(29) = -2.1, p = 0.046]. There were trend level differences in the Number-Combination test [t(29) = -1.9, p = 0.074] and in the Stroop interference task [t(29) = -1.9, p = 0.068]. No significant differences in visuospatial and working memory were found. Furthermore, the current mood state was better during high MR occupation compared to low MR occupation [t(29) = -2.4, p = 0.023] as was diastolic blood pressure [F(2, 29) = 3.6, p = 0.07].

CONCLUSIONS

Cognitive function and mood in patients with AI depend in part on MR occupation. Because the medium effect size indicates a potential clinical significance, further studies should systematically examine which dosages of fludrocortisone are associated with optimal cognitive function and mood in AI patients.

Chronic P-glycoprotein inhibition increases the brain concentration of escitalopram: potential implications for treating depression

Recent preclinical studies have revealed a functionally important role for the drug efflux pump P‐glycoprotein (P‐gp) at the blood–brain barrier in limiting brain levels and thus antidepressant‐like activity of certain antidepressant drugs. Specifically, acute administration of P‐gp inhibitors, such as verapamil and cyclosporin A (CsA), has been shown to augment brain concentrations and functional activity of the antidepressant escitalopram in rodents. However, depression is a chronic disorder and current treatments require prolonged administration to elicit their full therapeutic effect. Thus, it is important to investigate whether acute findings in relation to P‐gp inhibition translate to chronic paradigms. To this end, the present study investigates whether chronic treatment with the P‐gp inhibitor verapamil and the antidepressant escitalopram results in enhanced brain distribution and antidepressant‐like effects of escitalopram. Verapamil (10 mg·kg⁻¹ i.p.) and escitalopram (0.1 mg·kg⁻¹ i.p.) were administered once daily for 22 days. On the final day of treatment, brain regions and plasma were collected for analysis of cortical and plasma escitalopram concentrations, and to determine the hippocampal expression of genes previously reported to be altered by chronic antidepressant treatment. Verapamil treatment resulted in a greater than twofold increase in brain levels of escitalopram, without altering plasma levels. Neither gene expression analysis nor behavioral testing revealed an augmentation of responses to escitalopram treatment due to verapamil administration. Taken together, these data demonstrate for the first time that P‐gp inhibition can yield elevated brain concentrations of an antidepressant after chronic treatment. The functional relevance of these increased brain levels requires further elaboration.

Clinical and biochemical manifestations of depression: relation to the neurobiology of stress

Major depressive disorder (MDD) is a chronic, recurrent, and severe psychiatric disorder with high mortality and medical comorbidities. Stress-related pathways have been directly involved in the pathophysiology and treatment of MDD. The present paper provides an overview on the stress system as a model to understand key pathophysiological paradigms in MDD. These mechanisms involve behavioral, cognitive, and systemic manifestations and are also associated with the mechanisms of action of effective antidepressants. Aspects such as depression subtypes, inflammation, insulin resistance, oxidative stress, and prothrombotic states in critical brain circuits and periphery are critically appraised. Finally, new strategies for approaching treatment-resistant major depression and potential adverse effects associated with this complex and intricate network are highlighted. The authors used PubMed as the database for this review. Each author extracted relevant data and assessed the methodological quality of each study.

Effects of escitalopram/quetiapine combination therapy versus escitalopram monotherapy on hypothalamic-pituitary-adrenal-axis activity in relation to antidepressant effectiveness

The hypothalamic-pituitary-adrenocortical (HPA) system is believed to play an important role in the pathophysiology of major depressive disorder. In this context, the atypical antipsychotic quetiapine (QUE) has been shown to inhibit HPA system activity in healthy subjects. In this study we investigated whether the putative inhibitory effects of QUE on HPA system activity may contribute to its antidepressant efficacy. We analyzed the effects of QUE as an augmentation to the selective serotonin reuptake inhibitor (SSRI) escitalopram (ESC) on HPA system activity in comparison to a monotherapy with ESC in relation to the antidepressant effectiveness. HPA axis activity (cortisol and ACTH) was measured by means of the dexamethasone/corticotropin-releasing hormone (DEX/CRH) test which was performed before (week 0) and during (week 1, week 5) antidepressant psychopharmacotherapy. The combination therapy, but not the ESC monotherapy showed significantly inhibiting effects on HPA system activity leading to stepwise down-regulation. ACTH concentrations were reduced in the ESC/QUE group during five weeks of treatment. The inhibitory effect of QUE maybe involved in its antidepressant effects as an augmentation strategy.

Impact on cortisol and antidepressant efficacy of quetiapine and escitalopram in depression

BACKGROUND

In this study, the impact of quetiapine fumarate extended release (QXR) and escitalopram (ESC) on HPA axis activity was investigated in depressed patients in relationship to antidepressant efficacy.

METHODS

In a randomized, open-label 5-week trial 60 inpatients suffering from major depression (DSM-IV criteria) were treated for 5 weeks with either QXR (300 mg/day) or ESC (10mg/day). The dexamethasone/CRH (DEX/CRH) test was performed before treatment, after 1, and after 5 weeks of treatment. Cortisol (COR) AUC values were used to assess HPA axis function. The Hamilton Depression Rating Scale was used weekly to estimate antidepressant efficacy.

RESULTS

QXR and ESC showed comparable antidepressant effects but strongly differed in their impact on HPA axis activity. In the QXR group, a marked inhibition of COR AUC levels was observed which was most pronounced after one week of treatment but showed a partial re-increase after 5 weeks of treatment. In contrast, ESC transiently stimulated COR AUC values (week 1) whereas COR AUC levels at week 0 and week 5 were comparable. COR improvement at week 1 (defined as COR peak value reduction between DEX/CRH test 1 and 2) was significantly associated with better clinical outcome.

CONCLUSION

Apparently, different effects on HPA axis activity reflect distinct pharmacoendocrinological properties of psychotropic drugs.

Distribution of the glucocorticoid receptor in the human amygdala; changes in mood disorder patients

Exposure to stress activates the hypothalamic-pituitary-adrenal (HPA) axis that stimulates glucocorticoid (GC) release from the adrenal. These hormones exert numerous effects in the body and brain and bind to a.o. glucocorticoid receptors (GR) expressed in the limbic system, including the hippocampus and amygdala. Hyperactivity of the HPA axis and disturbed stress feedback are common features in major depression. GR protein is present in the human hypothalamus and hippocampus, but little is known-neither in healthy subjects nor in depressed patients-about GR expression in the amygdala, a brain structure involved in fear and anxiety. Since chronic stress in rodents affects GR expression in the amygdala, altered GR protein level in depressed versus healthy controls can be expected. To test this, we investigated GR-α protein expression in the post-mortem human amygdala and assessed changes in ten major or bipolar depressed patients and eight non-depressed controls. Abundant GR immunoreactivity was observed in the human amygdala, both in neurons and astrocytes, with a similar pattern in its different anatomical subnuclei. In major depression, GR protein level as well as the percentage of GR-containing astrocytes was significantly higher than in bipolar depressed patients or in control subjects. Taken together, the prominent expression of GR protein in the human amygdala indicates that this region can form an important target for corticosteroids and stress, while the increased GR expression in major, but not bipolar, depression suggests possible involvement in the etiology of major depression.

Nobiletin Ameliorates the Deficits in Hippocampal BDNF, TrkB, and Synapsin I Induced by Chronic Unpredictable Mild Stress

Background. Our previous study has demonstrated that nobiletin could reverse the behavioral alterations in stressed mice. However, the relation of its antidepressant-like action with neurotrophic molecular expression remains unknown. This study aimed to explore the antidepressant-like mechanism of nobiletin related to the neurotrophic system in rats exposed to chronic unpredictable mild stress (CUMS). Methods. Depressive-like anhedonia (assessed by sucrose preference) and serum corticosterone secretion were evaluated in the CUMS, followed by brain-derived neurotrophic factor (BDNF), its tropomyosin-related kinase receptor B (TrkB), and the downstream target synapsin I expressions in the hippocampus. Results. Anhedonia, which occurred within week 2, was rapidly ameliorated by nobiletin. While fluoxetine needed additional 2 weeks to improve the anhedonia. In addition, nobiletin administration for 5 weeks significantly ameliorated CUMS-induced increase in serum corticosterone levels. Furthermore, we also found that CUMS-induced deficits of hippocampal BDNF, TrkB, and synapsin I were ameliorated by nobiletin. Conclusions. Taken together, these findings suggest that nobiletin produces rapidly acting antidepressant-like responses in the CUMS and imply that BDNF-TrkB pathway may play an important role in the antidepressant-like effect of nobiletin.

The mineralocorticoid receptor agonist, fludrocortisone, differentially inhibits pituitary-adrenal activity in humans with psychotic major depression

INTRODUCTION

Hypothalamic-pituitary-adrenal (HPA) axis dysregulation has been linked with major depression, particularly psychotic major depression (PMD), with mineralocorticoid receptors (MRs) playing a role in HPA-axis regulation and the pathophysiology of depression. Herein we hypothesize that the MR agonist fludrocortisone differentially inhibits the HPA axis of psychotic major depression subjects (PMDs), non-psychotic major depression subjects (NPMDs), and healthy control subjects (HCs).

METHODS

Fourteen PMDs, 16 NPMDs, and 19 HCs were admitted to the Stanford University Hospital General Clinical Research Center. Serum cortisol levels were sampled at baseline and every hour from 18:00 to 23:00h, when greatest MR activity is expected, on two consecutive nights. On the second afternoon at 16:00h all subjects were given 0.5mg fludrocortisone. Mean cortisol levels pre- and post-fludrocortisone and percent change in cortisol levels were computed.

RESULTS

There were no significant group differences for cortisol at baseline: F(2,47)=.19, p=.83. There were significant group differences for post-fludrocortisone cortisol: F(2,47)=5.13, p=.01, which were significantly higher in PMDs compared to HCs (p=.007), but not compared to NPMDs (p=.18). There were no differences between NPMD's and HC's (p=.61). Also, PMDs had a lower percent change from baseline in cortisol levels at 2200h than NPMDs (p=.01) or HCs (p=.009).

CONCLUSIONS

Individuals with psychotic major depression compared to healthy control subjects have diminished feedback inhibition of the hypothalamic-pituitary-adrenal (HPA) axis in response to the mineralocorticoid receptor agonist fludrocortisone. To our knowledge, this is the first study to examine HPA axis response to MR stimulation in major depression (with and without psychosis), and only the third study to demonstrate that exogenously administered fludrocortisone can down-regulate the HPA axis in humans.

Effects of Hypericum perforatum extract on rat irritable bowel syndrome

CONTEXT

In irritable bowel syndrome (IBS), disturbance of bowel motility is associated with infiltration of inflammatory mediators and cytokines into the intestine, such as neutrophils, myeloperoxidase (MPO), tumor necrosis factor alfa (TNF-α), and lipid peroxide.

AIMS

Regarding promising anti-inflammatory and anti-oxidative effects of Hypericum perforatum (HP) extract, besides its anti-depressant effect, this study was designed to evaluate the effects of HP in an experimental model of IBS.

SETTINGS AND DESIGN

IBS was induced by a 5-day restraint stress in rats. The HP extract was administered by gavage in doses of 150, 300, and 450 mg/kg for 26 days. Fluoxetine and loperamide were used as positive controls. Gastric emptying and small bowel and colon transit, besides the levels of TNF-α, MPO, lipid peroxidation, and antioxidant power, were determined in colon homogenates.

STATISTICAL ANALYSIS USED

Data were analyzed by one-way ANOVA followed by Tukey's post hoc test for multiple comparisons.

RESULTS

A significant reduction in small bowel and colonic transit (450 mg/kg), TNF-α, MPO, and lipid peroxidation and an increase in antioxidant power in all HP-treated groups (150, 300, and 450 mg/kg) were seen as compared with the control group. Gastric emptying did not alter significantly when compared with the control group. Treatment with loperamide (10 mg/kg) significantly inhibited gastric emptying and small bowel and colonic transit, while flouxetine (10 mg/kg) decreased gastric emptying, TNF-α, MPO, and lipid peroxidation and increased the antioxidant power of the samples in comparison with the control group.

CONCLUSIONS

HP diminished the recruitment of inflammatory cells and TNF-α following restraint stress not in a dose-dependent manner, possibly via inhibition of MPO activity and increasing colon antioxidant power, without any difference with fluoxetine. The HP extract inhibits small bowel and colonic transit acceleration like loperamide but has minimal effect on gastric emptying.

Mineralocorticoid receptor overexpression facilitates differentiation and promotes survival of embryonic stem cell-derived neurons

Mineralocorticoid receptor (MR), highly expressed in the hippocampus, binds corticosteroid hormones and coordinately participates, with the glucocorticoid receptor, to the control of stress responses, memorization, and behavior. To investigate the impact of MR in neuronal survival, we generated murine embryonic stem (ES) cells that overexpress human MR (hMR) (P1-hMR) and are induced to differentiate into mature neurons. We showed that recombinant MR expression increased throughout differentiation and is 2-fold higher in P1-hMR ES-derived neurons compared with wild-type controls, whereas glucocorticoid receptor expression was unaffected. Although proliferation and early neuronal differentiation were comparable in P1-hMR and wild-type ES cells, MR overexpression was associated with higher late neuronal marker expression (microtubule-associated protein 2 and β-tubulin III). This was accompanied by a shift towards neuron survival with an increased ratio of anti- vs. proapoptotic molecules and 50% decreased caspase 3 activity. Knocking down MR overexpression by small interfering RNA drastically reversed neuroprotective effects with reduced Bcl(2)/Bax ratio and decreased microtubule-associated protein 2 expression. P1-hMR neurons were protected against oxidative stress-induced apoptosis through reduced caspase 3 activation and drastically increased Bcl(2)/Bax ratio and β-tubulin III expression. We demonstrated the involvement of MR in neuronal differentiation and survival and identify MR as an important neuroprotective mediator opening potential pharmacological strategies.

Toward a mechanistic understanding of how variability in neurobiology shapes individual differences in behavior

Research has begun to identify how variability in brain function contributes to individual differences in complex behavioral traits. Examining variability in molecular signaling pathways with emerging and established methodologies such as pharmacologic fMRI, multimodal PET/fMRI, and hormonal assays are beginning to provide a mechanistic understanding of how individual differences in brain function arise. Against this background, functional genetic polymorphisms are being utilized to understand the origins of variability in signaling pathways as well as to efficiently model how such emergent variability impacts behaviorally relevant brain function and health outcomes. This chapter provides an overview of a research strategy that integrates these complimentary levels of analysis; existing empirical data is used to illustrate the effectiveness of this approach in illuminating the mechanistic neurobiology of individual differences in complex behavioral traits. This chapter also discusses how such efforts can contribute to the identification of predictive risk markers that interact with unique environmental factors to precipitate psychopathology.

Neuropeptidomics of mouse hypothalamus after imipramine treatment reveal somatostatin as a potential mediator of antidepressant effects

Excessive activation of the hypothalamic-pituitary-adrenal (HPA) axis has been associated with numerous diseases, including depression, and the tricyclic antidepressant imipramine has been shown to suppress activity of the HPA axis. Central hypothalamic control of the HPA axis is complex and involves a number of neuropeptides released from multiple hypothalamic subnuclei. The present study was therefore designed to determine the effects of imipramine administration on the mouse hypothalamus using a peptidomics approach. Among the factors found to be downregulated after acute (one day) or chronic (21 days) imipramine administration were peptides derived from secretogranin 1 (chromogranin B) as well as peptides derived from cerebellin precursors. In contrast, peptides SRIF-14 and SRIF-28 (1-11) derived from somatostatin (SRIF, somatotropin release inhibiting factor) were significantly upregulated by imipramine in the hypothalamus. Because diminished SRIF levels have long been known to occur in depression, a second part of the study investigated the roles of individual SRIF receptors in mediating potential antidepressant effects. SRA880, an antagonist of the somatostatin-1 autoreceptor (sst1) which positively modulates release of endogenous SRIF, was found to synergize with imipramine in causing antidepressant-like effects in the tail suspension test. Furthermore, chronic co-administration of SRA880 and imipramine synergistically increased BDNF mRNA expression in the cerebral cortex. Application of SRIF or L054264, an sst2 receptor agonist, but not L803807, an sst4 receptor agonist, increased phosphorylation of CaMKII and GluR1 in cerebrocortical slices. Our present experiments thus provide evidence for antidepressant-induced upregulation of SRIF in the brain, and strengthen the notion that augmented SRIF expression and signaling may counter depressive-like symptoms. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Putative role of endocannabinoid signaling in the etiology of depression and actions of antidepressants

In the last few years, there have been several advances in the determination of the role of the endocannabinoid system in the etiology of depression and the functional actions of antidepressant drugs. Specifically, a deficiency in endocannabinoid signaling is sufficient to produce a "depressive-like" phenotype at the preclinical level (including changes in rewarding, emotional and cognitive behavior and biological changes such as increased HPA axis activity, impaired stress adaptation, reduced neurogenesis and altered serotonin negative feedback), and capable of inducing symptoms of depression in humans at a clinical level. In line with these findings, clinical populations diagnosed with depression are found to have reduced levels of circulating endocannabinoids and preclinical models of depression reveal a deficit in central endocannabinoid signaling. Moreover, facilitation of endocannabinoid signaling is sufficient to produce all of the behavioral and biochemical effects of conventional antidepressant treatments. Further, many forms of antidepressant treatments significantly alter endocannabinoid signaling, and in some of these cases this recruitment of endocannabinoid signaling is involved in the neuroadaptive effects of these treatments. Ultimately, these data present a compelling picture of the putative role of the endocannabinoid system in the processes subserving both the development and treatment of depression.

Effects of Hypericum perforatum extract on rat irritable bowel syndrome

CONTEXT

In irritable bowel syndrome (IBS), disturbance of bowel motility is associated with infiltration of inflammatory mediators and cytokines into the intestine, such as neutrophils, myeloperoxidase (MPO), tumor necrosis factor alfa (TNF-α), and lipid peroxide.

AIMS

Regarding promising anti-inflammatory and anti-oxidative effects of Hypericum perforatum (HP) extract, besides its anti-depressant effect, this study was designed to evaluate the effects of HP in an experimental model of IBS.

SETTINGS AND DESIGN

IBS was induced by a 5-day restraint stress in rats. The HP extract was administered by gavage in doses of 150, 300, and 450 mg/kg for 26 days. Fluoxetine and loperamide were used as positive controls. Gastric emptying and small bowel and colon transit, besides the levels of TNF-α, MPO, lipid peroxidation, and antioxidant power, were determined in colon homogenates.

STATISTICAL ANALYSIS USED

Data were analyzed by one-way ANOVA followed by Tukey's post hoc test for multiple comparisons.

RESULTS

A significant reduction in small bowel and colonic transit (450 mg/kg), TNF-α, MPO, and lipid peroxidation and an increase in antioxidant power in all HP-treated groups (150, 300, and 450 mg/kg) were seen as compared with the control group. Gastric emptying did not alter significantly when compared with the control group. Treatment with loperamide (10 mg/kg) significantly inhibited gastric emptying and small bowel and colonic transit, while flouxetine (10 mg/kg) decreased gastric emptying, TNF-α, MPO, and lipid peroxidation and increased the antioxidant power of the samples in comparison with the control group.

CONCLUSIONS

HP diminished the recruitment of inflammatory cells and TNF-α following restraint stress not in a dose-dependent manner, possibly via inhibition of MPO activity and increasing colon antioxidant power, without any difference with fluoxetine. The HP extract inhibits small bowel and colonic transit acceleration like loperamide but has minimal effect on gastric emptying.

Gender-specific response of brain corticosteroid receptors to stress and fluoxetine

Gender-related differences in dexamethasone binding to corticosteroid receptors (CR) and in glucocorticoid receptor (GR) protein level in the pituitary, hypothalamus, hippocampus and prefrontal cortex were studied before and after antidepressant fluoxetine administration to both unstressed and rats exposed to a chronic social isolation stress. Untreated males, in comparison to females, displayed higher hormone-binding capacity of both GR and mineralocorticoid receptor (MR) in the hippocampal cytosol, as well as higher GR protein level in the pituitary cytosol. In both genders, dexamethasone binding to MR exceeded that to GR. While fluoxetine treatment and social isolation had no effect on GR activity, the influence on MR was gender-specific. Fluoxetine facilitated MR hormone-binding only in females, increasing the MR/GR activity ratio. In contrast, after a 6-week isolation of males, MR binding capacity was diminished and MR/GR ratio inverted in favor of GR. In addition, fluoxetine induced elevation of cytosolic GR protein level in the pituitary and hypothalamus, the latter change being gender-specific. The results point to gender-related differences in the CRs functioning and suggest that both MR and GR may contribute to well-known sexual dimorphism in vulnerability to stress and stress-related disorders and in the outcome of antidepressant treatment.

Do stress hormones connect environmental effects with behavior in the forced swim test?

Forced swim test (FST) is a widely used test for antidepressant development. Depression is a stress related disease, as hormones of the stress-axis can modify mood. However it is not clear, how the appearance of depressive-like behavior (floating) in FST is connected with changes in the stress-hormone levels. We hypothesized, that different manipulations would alter the behavior through changes in stress-hormone levels. First the effect of environmental alterations was studied. Increasing water-temperature enhanced floating time together with a decrease in adrenocorticotropin levels. During the dark phase of the day rats spent more time with floating independently from the actual lighting. Neither the phase nor the actual lighting had significant effect on adrenocorticotropin concentrations with higher corticosterone levels during the dark phase. At greater water depth rats float less but the size of animals had no effect. Water depth did not influence adrenocorticotropin and corticosterone responses, but the size of the rats significantly affected both factors. Secondly, administration of imipramine reduced floating and adrenocorticotropin level without affecting corticosterone. Despite the known connection between depression and stress we did not find a correlation between floating behavior and hormone levels. As an alternative mechanism imipramine-induced heart rate and core body temperature decrease was found by telemetric approach. This study is the first summary in rats examining the effect of wide range of environmental alterations during FST. It seems likely that both brain monoamines and stress-axis take part in the development of depression, but these pathways are regulated independently.

Cognitive correlates of hypothalamic-pituitary-adrenal axis in major depression

Depressive disorder has become a major health problem and is ranked among the leading causes of disability worldwide. Depression-related cognitive impairment contributes to loss of economic productivity and psychosocial functioning and calls for more efficient treatment strategies. Although the pathogenesis of cognitive impairments in patients with major depressive disorder (MDD) is still insufficiently understood, increasing evidence implicates hypothalamus-pituitary-adrenal (HPA) axis as an important neurobiological determinant of cognitive impairment in depression. In this article, major findings of both HPA axis function abnormalities and cognitive impairments in depressed patients are summarized, focusing on their inter-relationship. Novel approaches in pharmacotherapy and psychotherapy have emerged which will be discussed with regard to their ability to reinstate normal HPA axis function in MDD and to treat cognitive impairments in MDD.

The hypothalamic-pituitary-adrenal axis and serotonin abnormalities: a selective overview for the implications of suicide prevention

Suicidal behavior and mood disorders are one of the world's largest public health problems. The biological vulnerability for these problems includes genetic factors involved in the regulation of the serotonergic system and stress system. The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system that regulates the body's response to stress and has complex interactions with brain serotonergic, noradrenergic and dopaminergic systems. Corticotropin-releasing hormone and vasopressin act synergistically to stimulate the secretion of ACTH that stimulates the biosynthesis of corticosteroids such as cortisol from cholesterol. Cortisol is a major stress hormone and has effects on many tissues, including on mineralocorticoid receptors and glucocorticoid receptors in the brain. Glucocorticoids produce behavioral changes, and one important target of glucocorticoids is the hypothalamus, which is a major controlling center of the HPA axis. Stress plays a major role in the various pathophysiological processes associated with mood disorders and suicidal behavior. Serotonergic dysfunction is a well-established substrate for mood disorders and suicidal behavior. Corticosteroids may play an important role in the relationship between stress, mood changes and perhaps suicidal behavior by interacting with 5-HT1A receptors. Abnormalities in the HPA axis in response to increased levels of stress are found to be associated with a dysregulation in the serotonergic system, both in subjects with mood disorders and those who engage in suicidal behavior. HPA over-activity may be a good predictor of mood disorders and perhaps suicidal behavior via abnormalities in the serotonergic system.

Nuclear orphan receptor Nor-1 contributes to depressive behavior in the Wistar-Kyoto rat model of depression

The current study explored the effects of prolonged antidepressant treatment on mRNA levels of two nuclear receptors in specific brain regions of an animal model of depression, the Wistar-Kyoto (WKY) rat. Both nuclear receptors have been implicated in the development or treatment of depression. The expression of nuclear orphan receptor-1 (Nor-1), a member of the NR4A nuclear orphan receptor family, is induced by electroconvulsive shock, an effective treatment for depression. Deficit in the levels or function of the glucocorticoid receptor (GR) found in depressed patients has been causally implicated in depression, as this deficit is normalized by antidepressant treatments. Baseline levels of amygdalar Nor-1 and GR mRNA were higher in the WKYs compared to the comparison control Sprague-Dawley rats (SD). Prolonged treatment with the antidepressant desipramine (DMI) decreased the expression of both transcripts in the WKY strain concomitantly with decreased immobility in the forced swim test (FST) of depressive behavior. Using short hairpin RNA (shRNA) targeted against Nor-1, we investigated the direct contribution of elevated Nor-1 expression in the amygdala of WKY to their exaggerated depressive behavior in the FST. After validating the shRNA targeting of Nor-1 in vitro, Nor-1 shRNA containing vector was infused intracerebroventricularly, using a linear polyethylenimine (PEI)-containing in vivo gene delivery system. Repeated administration of Nor-1 shRNA ameliorated the depressive behavior of WKYs in the FST and decreased amygdalar Nor-1 mRNA levels without affecting GR mRNA levels. These data demonstrate that brain region-specific changes in GR expression in response to DMI are strain dependent and that elevated amygdalar Nor-1 expression can contribute to depressive behavior in the WKY model of depression.

Aberrant REST-mediated transcriptional regulation in major depressive disorder

There is growing evidence that aberrant transcriptional regulation is one of the key components of the pathophysiology of mood disorders. The repressor element-1 silencing transcription factor (REST) is a negative regulator of genes that contain the repressor element-1 (RE-1) binding site. REST has many target genes, including corticotropin releasing hormone (CRH), brain-derived neurotrophic factor, serotonin 1A receptor, which are suggested to be involved in the pathophysiology of depression and the action of antidepressants. However, a potential role for REST-mediated transcriptional regulation in mood disorders remains unclear. In this study, we examined the mRNA levels of REST and its known and putative target genes, using quantitative real-time PCR in peripheral blood cells of patients with major depressive and bipolar disorders in both a current depressive and a remissive state. We found reduced mRNA expression of REST and increased mRNA expression of CRH, adenylate cyclase 5, and the tumor necrosis factor superfamily, member 12-13 in patients with major depressive disorder in a current depressive state, but not in a remissive state. Altered expression of these mRNAs was not found in patients with bipolar disorder. Our results suggest that the aberrant REST-mediated transcriptional regulation of, at least, CRH, adenylate cyclase 5, and tumor necrosis factor superfamily, member 12-13, might be state-dependent and associated with the pathophysiology of major depression.

Modulation of the mineralocorticoid receptor as add-on treatment in depression: a randomized, double-blind, placebo-controlled proof-of-concept study

Preclinical and clinical studies have suggested a role of the mineralocorticoid receptor (MR) in the response to antidepressants. We tested in a proof-of-concept study whether adding fludrocortisone (an MR agonist) or spironolactone (an MR antagonist) accelerates onset of action and improves efficacy of escitalopram in patients with major depression. We included 64 in- and outpatients with major depression (Hamilton Depression Scale-17 score>18) in a double-blind, randomized, placebo-controlled trial. Patients were randomized in a 2:2:1 fashion to fludrocortisone (0.2 mg/d, n=24) or spironolactone (100 mg/d, n=27) or placebo (n=13) for the first 3 weeks during a 5-week treatment with escitalopram. No differences in mean HAMD change scores and in time to response emerged between treatments. However, among the responders, patients treated with fludrocortisone responded faster (Breslow test, p=0.05). The mean number of days to response was 16.0+/-2.6 days vs. placebo 22.2+/-2.0 vs. spironolactone 22.6+/-2.3 (F=3.78, p=0.03). In the whole group, plasma cortisol increased during spironolactone and decreased during fludrocortisone treatment (F=2.4, p=0.04). In patients treated with fludrocortisone, non-responders had elevated cortisol values compared to responders throughout the study period (F=5.1, p=0.04). Stimulation of MR with fludrocortisone as adjunct to escitalopram accelerated the response in the group of responders while no effect emerged in the sample as a whole. A larger randomized controlled trial is warranted.

Effect of co-administration of fluoxetine and amantadine on immunoendocrine parameters in rats subjected to a forced swimming test

Considerable attention has been paid to a possible role of immunological dysregulation in the pathogenesis of depression. It has been reported that combined administration of antidepressant drugs and the non-competitive NMDA receptor antagonist amantadine reduces immobility time in the forced swimming test (FST). Moreover, preliminary clinical data show that such a combination of drugs has a beneficial effect on treatment-resistant depressed patients. Since immune activation and a pro-inflammatory response are clearly evident in treatment-resistant depression, the aim of the present study was to examine the effect of a combination of the antidepressant fluoxetine and amantadine on immunoendocrine parameters in rats subjected to the forced swimming test. The obtained results revealed synergistic antidepressant effects of the combined administration of fluoxetine (10 mg/kg) and amantadine (10 mg/kg) - drugs otherwise ineffective when given separately in the above doses. Antidepressant activity was accompanied with a significant decrease in the capacity of splenocytes to proliferate in response to concanavalin A. Moerover, fluoxetine and the combination of amantadine and fluoxetine reduced relative spleen weight in rats subjected to the FST, compared to rats treated with the vehicle. The combination of amantadine and fluoxetine enhanced the production of the negative immunoregulator interleukin-10 (but not interferon-gamma) in rats subjected to the FST. The exposure to the FST produced an increase in plasma corticosterone levels, which was significantly attenuated by pretreatment with fluoxetine and amantadine. In summary, the antidepressive efficacy of a combination of fluoxetine and amantadine given in suboptimal doses may be related to the negative immunoendocrine effects of these drugs.