Modulation of serotonin transporter function by interleukin-4

Duloxetine improves chronic orofacial pain and comorbid depressive symptoms in association with reduction of serotonin transporter protein through upregulation of ubiquitinated serotonin transporter protein

ABSTRACT

Chronic orofacial pain (COP) is relieved by duloxetine (DLX) and frequently causes depressive symptoms. The aim of this study was to confirm effects of DLX on pain and depressive symptoms, and to associate with their effectiveness in platelet serotonin transporter (SERT) expression, which is a target molecule of DLX and plasma serotonin concentration in COP patients with depressive symptoms. We assessed for the severity of pain and depressive symptoms using the Visual Analog Scale (VAS) and 17-item Hamilton Depression Rating Scale (HDRS), respectively. Chronic orofacial pain patients were classified into 2 groups based on their HDRS before DLX-treatment: COP patients with (COP-D) and without (COP-ND) depressive symptoms. We found that the VAS and HDRS scores of both groups were significantly decreased after DLX treatment compared with those before DLX treatment. Upregulation of total SERT and downregulation of ubiquitinated SERT were observed before DLX treatment in both groups compared with healthy controls. After DLX treatment, there were no differences in total SERT of both groups and in ubiquitinated SERT of COP-D patients compared with healthy controls; whereas, ubiquitinated SERT of COP-ND patients remained downregulated. There were positive correlations between changes of serotonin concentrations and of VAS or HDRS scores in only COP-D patients. Our findings indicate that DLX improves not only pain but also comorbid depressive symptoms of COP-D patients. Duloxetine also reduces platelet SERT through upregulation of ubiquitinated SERT. As the result, decrease of plasma serotonin concentrations may be related to the efficacy of DLX in relieving pain and depression in COP patients.

Intranasal administration of interleukin-4 ameliorates depression-like behavior and biochemical alterations in mouse submitted to the chronic unpredictable mild stress: modulation of neuroinflammation and oxidative stress

Physical and psychological stress modulates the hypothalamic pituitary adrenal (HPA) axis, and the redox and inflammatory systems. Impairments in these systems have been extensively reported in major depression (MD) patients. Therefore, our study aimed to investigate the effects of the intranasal administration of interleukin-4 (IL-4) in mice with depressive-like behavior induced by chronic unpredictable mild stress (CUMS) for 28 days. On the 28th day, mice received IL-4 intranasally (1 ng/mouse) or vehicle (sterile saline), and after 30 min, they were submitted to behavioral tests or euthanasia for blood collection and removal of the adrenal glands, axillary lymph nodes, spleen, thymus, prefrontal cortices (PFC), and hippocampi (HC). A single administration of IL-4 reversed CUMS-induced depression-like behavior in the tail suspension test and splash test, without evoking locomotor changes. IL-4 administration reduced the plasma levels of corticosterone and the increased weight of suprarenal glands in stressed mice. Moreover, IL-4 restored the expression of nuclear factor erythroid 2-related factor 2 (NRF2), nuclear factor kappa B (NF-kB), interleukin 1 beta (IL-1β), IL-4, brain derived neurotrophic factor (BDNF), and indoleamine 2,3-dioxygenase (IDO) in the PFC and HC and modulated oxidative stress markers in these brain structures in stressed mice. Our results showed for the first time the antidepressant-like effect of IL-4 through the modulation of neuroinflammation and oxidative stress. The potential effect of IL-4 administered intranasally arises as an innovative strategy for MD treatment.

High-fat diet induces neuroinflammation and reduces the serotonergic response to escitalopram in the hippocampus of obese rats

Clinical studies indicate that obese individuals have an increased risk of developing co-morbid depressive illness and that these patients have reduced responses to antidepressant therapy, including selective serotonin reuptake inhibitors (SSRIs). Obesity, a condition of chronic mild inflammation including obesity-induced neuroinflammation, is proposed to contribute to decreases in synaptic concentrations of neurotransmitters like serotonin (5HT) by decreasing 5HT synthesis in the dorsal raphe nucleus (DRN) and/or affecting 5HT reuptake in DRN target regions like the hippocampus. In view of these observations, the goal of the current study was to examine inflammatory markers and serotonergic dynamics in co-morbid obesity and depression. Biochemical and behavioral assays revealed that high-fat diet produced an obesity and depressive-like phenotype in one cohort of rats and that these changes were marked by increases in key pro-inflammatory cytokines in the hippocampus. In real time using fast scan cyclic voltammetry (FSCV), we observed no changes in basal levels of hippocampal 5HT; however responses to escitalopram were significantly impaired in the hippocampus of obese rats compared to diet resistant rats and control rats. Further studies revealed that these neurochemical observations could be explained by increases in serotonin transporter (SERT) expression in the hippocampus driven by elevated neuroinflammation. Collectively, these results demonstrate that obesity-induced increases in neuroinflammation adversely affect SERT expression in the hippocampus of obese rats, thereby providing a potential synaptic mechanism for reduced SSRI responsiveness in obese subjects with co-morbid depressive illness.

Long-term evaluation of temporomandibular disorders in association with cytokine and autoantibody status in young women

Temporomandibular disorders (TMD) is a chronic pain disease affecting 4-60% of general population. Its suggested etiology includes mechanical overloading to related structures, psychosocial factors, and genetic vulnerability. However, its pathogenesis is yet to be fully understood, especially in cases with a higher level of pain and more associated comorbidities. Recently chronic systemic inflammation and possible autoimmunity has been indicated in several pain conditions as the underlying mechanism of chronicity but this aspect has not been rigorously investigated in TMD. This article focuses on analyzing the levels of cytokines, chemokines, autoantibodies and nonspecific inflammatory markers and comparing their levels according to pain severity and duration in 66 female TMD patients in their 20 s and investigating their association with clinical indices of TMD and comorbidities. The high pain disability group showed decreased range of jaw function and more pain on palpation of capsule areas compared to the low pain disability group. Comorbidities such as anxiety and sleep disturbance were also significantly more prevalent. The level of IL-8 and IgG were significantly higher in the high pain disability group. IL-2, -8, -13, IFN- γ, RANTES, PGE2, and thrombopoietin levels showed a significant effect on indices reflecting jaw function, generalized pain intensity, and health related quality of life. Such results imply that longer pain duration and higher pain intensity is associated with higher levels of systemic inflammation suggesting the possible role of immunologic disturbance as an underlying factor of chronic TMD pain and warranting further investigation for its consideration in diagnosis and treatment.

Anatomical and neurochemical organization of the serotonergic system in the mammalian brain and in particular the involvement of the dorsal raphe nucleus in relation to neurological diseases

The brainstem is a neglected brain area in neurodegenerative diseases, including Alzheimer's and Parkinson's disease, frontotemporal lobar degeneration and autonomic dysfunction. In Depression, several observations have been made in relation to changes in one particular the Dorsal Raphe Nucleus (DRN) which also points toward as key area in various age-related and neurodevelopmental diseases. The DRN is further thought to be related to stress regulated processes and cognitive events. It is involved in neurodegeneration, e.g., amyloid plaques, neurofibrillary tangles, and impaired synaptic transmission in Alzheimer's disease as shown in our autopsy findings. The DRN is a phylogenetically old brain area, with projections that reach out to a large number of regions and nuclei of the central nervous system, particularly in the forebrain. These ascending projections contain multiple neurotransmitters. One of the main reasons for the past and current interest in the DRN is its involvement in depression, and its main transmitter serotonin. The DRN also points toward the increased importance and focus of the brainstem as key area in various age-related and neurodevelopmental diseases. This review describes the morphology, ascending projections and the complex neurotransmitter nature of the DRN, stressing its role as a key research target into the neural bases of depression.

NRG1, PIP4K2A, and HTR2C as Potential Candidate Biomarker Genes for Several Clinical Subphenotypes of Depression and Bipolar Disorder

GSK3B, BDNF, NGF, NRG1, HTR2C, and PIP4K2A play important roles in molecular mechanisms of psychiatric disorders. GSK3B occupies a central position in these molecular mechanisms and is also modulated by psychotropic drugs. BDNF regulates a number of key aspects in neurodevelopment and synaptic plasticity. NGF exerts a trophic action and is implicated in cerebral alterations associated with psychiatric disorders. NRG1 is active in neural development, synaptic plasticity, and neurotransmission. HTR2C is another important psychopharmacological target. PIP4K2A catalyzes the phosphorylation of PI5P to form PIP2, the latter being implicated in various aspects of neuronal signal transduction. In the present study, the six genes were sequenced in a cohort of 19 patients with bipolar affective disorder, 41 patients with recurrent depressive disorder, and 55 patients with depressive episode. The study revealed a number of genetic variants associated with antidepressant treatment response, time to recurrence of episodes, and depression severity. Namely, alleles of rs35641374 and rs10508649 (NRG1 and PIP4K2A) may be prognostic biomarkers of time to recurrence of depressive and manic/mixed episodes among patients with bipolar affective disorder. Alleles of NC_000008.11:g.32614509_32614510del, rs61731109, and rs10508649 (also NRG1 and PIP4K2A) seem to be predictive biomarkers of response to pharmacological antidepressant treatment on the 28th day assessed by the HDRS-17 or CGI-I scale. In particular, the allele G of rs10508649 (PIP4K2A) may increase resistance to antidepressant treatment and be at the same time protective against recurrent manic/mixed episodes. These results support previous data indicating a biological link between resistance to antidepressant treatment and mania. Bioinformatic functional annotation of associated variants revealed possible impact for transcriptional regulation of PIP4K2A. In addition, the allele A of rs2248440 (HTR2C) may be a prognostic biomarker of depression severity. This allele decreases expression of the neighboring immune system gene IL13RA2 in the putamen according to the GTEx portal. The variant rs2248440 is near rs6318 (previously associated with depression and effects of psychotropic drugs) that is an eQTL for the same gene and tissue. Finally, the study points to several protein interactions relevant in the pathogenesis of mood disorders. Functional studies using cellular or animal models are warranted to support these results.

Novel harmala-ocudelic tuning (HOT) for ocular disorders

The eye contains serotonin, and possesses serotonergic receptors and modulators. Selective serotonin reuptake inhibitors (SSRIs) may impair ocular function, while other serotonin receptor-binding drugs might improve it. A putative vision-improving drug must be safe at therapeutic doses, most preferably with long-lasting benefits from a single or very few administration(s). One drug potentially satisfying these criteria is the common, botanically-occurring indole alkaloid and "major hallucinogen," harmine. Harmine is prominent in the leaves of the Generally Recognized as Safe (GRAS) Passiflora, and in Peganum and Banisteriopsis, the two preeminent "sacred" medicinal plants of India/pre-Islamic Persia/modern Iran and the Amazon respectively. Though the possibility of drug-drug or herb-drug interactions exists, especially with SSRIs, at correct patient-individualized dosages, these plants, used alone, are minimally hallucinogenic, well tolerated, potentially exerting profound therapeutic effects on vision from a single or few administration(s) lasting months or years. The hypothesized mechanism for this extraordinary action is tuning of the serotonergic receptors in the eye in their binding affinity for serotonin, a putative neurochemical "ocudelic" homologue to the psychedelic phenomenon, likely potentiated, according to clinical experience with classical hallucinogens, by therapeutic music, positive psychological "set," and conducive environmental "setting." Blinded research with harmala alkaloid-containing plants in ocular patients using psychedelic therapy accoutrements, viz. eyeshades, high fidelity classical music, headphones, two guides, pre-dosing preparation, and post-dosing integration, could non-invasively assess visual acuity in presbyopia. Significant results would stimulate further exploration of this novel approach to ocular disorders. Deeper benefit, particularly when the retina is compromised, might follow co-ingestion of the harmala alkaloid-containing plants with plants containing dimethyltryptamine.

Neuron-glia interaction through Serotonin-BDNF-NGFR axis enables regenerative neurogenesis in Alzheimer's model of adult zebrafish brain

It was recently suggested that supplying the brain with new neurons could counteract Alzheimer’s disease (AD). This provocative idea requires further testing in experimental models in which the molecular basis of disease-induced neuronal regeneration could be investigated. We previously found that zebrafish stimulates neural stem cell (NSC) plasticity and neurogenesis in AD and could help to understand the mechanisms to be harnessed for developing new neurons in diseased mammalian brains. Here, by performing single-cell transcriptomics, we found that amyloid toxicity-induced interleukin-4 (IL4) promotes NSC proliferation and neurogenesis by suppressing the tryptophan metabolism and reducing the production of serotonin. NSC proliferation was suppressed by serotonin via down-regulation of brain-derived neurotrophic factor (BDNF)-expression in serotonin-responsive periventricular neurons. BDNF enhances NSC plasticity and neurogenesis via nerve growth factor receptor A (NGFRA)/ nuclear factor 'kappa-light-chain-enhancer' of activated B-cells (NFkB) signaling in zebrafish but not in rodents. Collectively, our results suggest a complex neuron-glia interaction that regulates regenerative neurogenesis after AD conditions in zebrafish.

Can regeneration of lost neurons counteract neurodegenerative disease? This study shows that serotonergic neurons alter neural stem cell proliferation and neurogenesis via a complex neuron-glia interaction involving interleukin-4, BDNF and NGF receptor in a zebrafish model of Alzheimer's disease.

The effects of acute aerobic exercise on mood and inflammation in individuals with multiple sclerosis and incomplete spinal cord injury

BACKGROUND

Spinal cord injury (SCI) and multiple sclerosis (MS) are associated with increased risks of depression. Acute exercise may improve mood in these populations via its affect on inflammation.

OBJECTIVE

To determine if acute exercise can positively affect mood in individuals with SCI and MS, and whether exercise-induced changes in inflammation contribute to such improvements.

METHODS

Thirteen participants completed 30 minutes of moderate-intensity exercise. Mood data (POMS questionnaire) and blood samples were taken before and after exercise, and blood was analyzed for inflammatory mediators and kynurenine pathway metabolites.

RESULTS

There was a significant reduction in total mood disturbance (TMD) pre to post-exercise, and pre to one-hour post-exercise. There was a significant decrease in TNF-α from pre to post-exercise, with further reductions one-hour post-exercise. There were no correlations between changes in TMD and changes in inflammation. However, changes in certain cytokines showed significant or trending correlations with changes in subsets of the POMS. Likewise, there was a trend for a correlation between exercise-induced changes in KYN/TRP and depression (p = 0.096).

CONCLUSIONS

Acute exercise can positively affect mood after SCI and MS, and this change may be partially accounted for by exercise-induced changes in inflammation. This relationship may be, in part, kynurenine pathway-dependent.

Estimating causal associations of atopic dermatitis with depression using the propensity score method: an analysis of Korea Community Health Survey data, 2010-2013

OBJECTIVES

Numerous studies have reported associations between atopic dermatitis (AD) and depression, but the causal relationship between the 2 diseases has not been established. Therefore, this study used the propensity score method to investigate whether there was a positive causal effect of AD on depression in 16 regions (cities and provinces) in Korea.

METHODS

The study analyzed 16 regions (cities and provinces) in Korea, using data obtained from the Korea Community Health Survey for the years 2010-2013. Propensity score matching was used to estimate the causal influence of AD on depression in Korea.

RESULTS

After propensity score matching, the standardized difference for each covariate among the 16 regions (cities and provinces) was less than 1, indicating a balance between the case and control groups. At the national level, those diagnosed with AD had a 2.31 times higher risk for being diagnosed with depression than those who had not been diagnosed with AD. In particular, the risk was highest in North Jeolla Province (odds ratio [OR], 4.87; 95% confidence interval [CI], 2.28 to 10.43) and lowest in Gwangju (OR, 1.82; 95% CI, 0.87 to 3.79), and the OR for Seoul was 2.23 (95% CI, 1.66 to 2.99).

CONCLUSIONS

This study provides insights into how causal inferences can be derived from observational studies, through an analysis of Korea Community Health Survey data. Furthermore, the study results have implications for region-specific guidelines for preventive health policies targeting depression.

Immune and Neuroprotective Effects of Physical Activity on the Brain in Depression

Physical activity-a lifestyle factor that is associated with immune function, neuroprotection, and energy metabolism-modulates the cellular and molecular processes in the brain that are vital for emotional and cognitive health, collective mechanisms that can go awry in depression. Physical activity optimizes the stress response, neurotransmitter level and function (e.g., serotonergic, noradrenergic, dopaminergic, and glutamatergic), myokine production (e.g., interleukin-6), transcription factor levels and correlates [e.g., peroxisome proliferator-activated receptor C coactivator-1α [PGC-1α], mitochondrial density, nitric oxide pathway activity, Ca2+ signaling, reactive oxygen specie production, and AMP-activated protein kinase [AMPK] activity], kynurenine metabolites, glucose regulation, astrocytic health, and growth factors (e.g., brain-derived neurotrophic factor). Dysregulation of these interrelated processes can effectuate depression, a chronic mental illness that affects millions of individuals worldwide. Although the biogenic amine model has provided some clinical utility in understanding chronic depression, a need remains to better understand the interrelated mechanisms that contribute to immune dysfunction and the means by which various therapeutics mitigate them. Fortunately, convergent evidence suggests that physical activity improves emotional and cognitive function in persons with depression, particularly in those with comorbid inflammation. Accordingly, the aims of this review are to (1) underscore the link between inflammatory correlates and depression, (2) explicate immuno-neuroendocrine foundations, (3) elucidate evidence of neurotransmitter and cytokine crosstalk in depressive pathobiology, (4) determine the immunomodulatory effects of physical activity in depression, (5) examine protocols used to effectuate the positive effects of physical activity in depression, and (6) highlight implications for clinicians and scientists. It is our contention that a deeper understanding of the mechanisms by which inflammation contributes to the pathobiology of depression will translate to novel and more effective treatments, particularly by identifying relevant patient populations that can benefit from immune-based therapies within the context of personalized medicine.

[Effect of cytokine genes and season of birth on personality]

AIM

To evaluate the interaction effects of season of birth and immune system genes on the personality traits 'Novelty seeking' (NS) and 'Self-directedness' (SD). Based on results on an influence of the immune system on the brain processes, the authors hypothesized that the interaction of immune system genes and season of birth, which is relevant for immune phenotype, can contribute to the development of personality traits.

MATERIAL AND METHODS

NS and SD were measured in 336 healthy volunteers, aged from 16 to 67 years, using the Temperament and Character Inventory (TCI-125). IL1B C3954T, IL4 C-589T, IL13 C1112T and TNFA G-308A polymorphisms were genotyped.

RESULTS

An interaction effect of IL4 C-589T and season of birth on the personality traits was found (F2,322=6.03, pcorr=0.011, η2=0.04). Carriers of the minor allele T, who were born in winter, had lower NS and higher SD. There was a nominal main effect of genotype on SD (F=5.44, p=0.020) as well, with higher SD scores in carriers of the allele T compared to the CC genotype.

CONCLUSION

The results suggest that the etiology of personality and immune characteristics can share common genetic elements including IL-4.

Beyond Self-Report: Performance Measures of Emotional Competencies Predict Symptoms of Depression and Anxiety, Physical Symptoms, Self-Rated Health, and Immunoregulatory Molecules

BACKGROUND

Most work testing links between emotional competencies and health has focused on self-reported and/or trait assessments. However, more objective assessments of skills and knowledge may also predict health relevant outcomes.

PURPOSE

The current study investigated whether performance-based tests of emotional knowledge and expressive skill predicted symptoms of depression and anxiety, self-reported physical symptoms, perceived health, and a range of immunoregulatory molecules.

METHODS

Eighty females aged 18-35 completed self-report assessments before attending a testing session in which they provided blood samples and completed performance-based assessments of expressive skill and emotional knowledge.

RESULTS

Greater expressive skill predicted better self-reported outcomes, but links to immunoregulatory molecules were mixed. Expressive skill for contempt and anger predicted higher, whereas skill for happiness predicted lower, concentrations of immunoregulatory molecules.

CONCLUSIONS

These data highlight the need to extend research beyond self-reported emotional competencies and suggest that performance-based skill and knowledge metrics may be associated with health relevant outcomes.

Immune System Activation and Depression: Roles of Serotonin in the Central Nervous System and Periphery

Serotonin (5-hydroxytryptamine, 5-HT) has long been recognized as a key contributor to the regulation of mood and anxiety and is strongly associated with the etiology of major depressive disorder (MDD). Although more known for its roles within the central nervous system (CNS), 5-HT is recognized to modulate several key aspects of immune system function that may contribute to the development of MDD. Copious amounts of research have outlined a connection between alterations in immune system function, inflammation status, and MDD. Supporting this connection, peripheral immune activation results in changes in the function and/or expression of many components of 5-HT signaling that are associated with depressive-like phenotypes. How 5-HT is utilized by the immune system to effect CNS function and ultimately behaviors related to depression is still not well understood. This Review summarizes the evidence that immune system alterations related to depression affect CNS 5-HT signaling that can alter MDD-relevant behaviors and that 5-HT regulates immune system signaling within the CNS and periphery. We suggest that targeting the interrelationships between immune and 5-HT signaling may provide more effective treatments for subsets of those suffering from inflammation-associated MDD.

Interleukin-4 is a participant in the regulation of depressive-like behavior

Inflammatory immune activation has been frequently associated with the development of major depression. Microglia might serve as an important interface in this immune system-to-brain communication. Interleukin-4, the major Th2 type cytokine, might be protective against depression due to its ability to counter-regulate inflammation and to inhibit serotonin transporter activity. By using an Interferon-α mouse model, we show that a decreased IL-4 responsiveness of microglia was specifically related to the development of depressive-like behavior. IL-4 deficient mice in a BALB/cJ background showed a considerable increase of depressive-like behavior in the forced swim (FST) and tail suspension test (TST) and reduced avoidance behavior in an active avoidance task. Prior conditioning with unescapable foot shocks further decreased avoidance behavior (learned helplessness) but to a similar level as in the wild type strain. IFN-α treatment was not able to further enhance the already increased level of depressive-like behavior in the FST and TST. Thus, IL-4 seems to be a critical participant in the regulation of depressive-like behavior in an untreated baseline condition. Increase of depressive-like behavior during inflammation in wild-type mice might be mediated to some extent by a reduction of IL-4 signaling.

The relationship between suicidal behaviors and atopic dermatitis in Korean adolescents

Atopic dermatitis is a common skin disease in adolescents, which may have a negative effect on the mental and emotional health. We investigated the relationship between atopic dermatitis and suicidal behaviors in Korean adolescents. Participants included 74,186 adolescents (38,221 boys and 35,965 girls) in middle and high school who completed the Eighth Korea Youth Risk Behavior Web-Based Survey. There were significant associations between atopic dermatitis and suicidal behaviors for girls. The overestimation of weight perception might have an additive impact on suicidal risk among girls. However, there were no significant associations between atopic dermatitis and suicidal behaviors in boys.

Association between the serotonin transporter and cytokines: Implications for the pathophysiology of bipolar disorder

BACKGROUND

Reduced brain serotonin transporter (SERT) has been demonstrated in bipolar disorder (BD). The aim of this study was to explore the potential role of cytokines on reduced SERT in BD.

METHODS

Twenty-eight BD type I patients and 28 age- and gender-matched healthy controls (HCs) were recruited. Single photon emission computed tomography with the radiotracer 123I ADAM was used for SERT imaging. Regions of interest included the midbrain, thalamus, putamen and caudate. Seven cytokines, including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1α (IL-1α), IL-1β, IL-4, IL-6 and IL-10, were measured using an enzyme linked immune-sorbent assay.

RESULTS

SERT availability in the midbrain and caudate was significantly lower in BD compared to HCs. IL-1β was significantly lower, whereas IL-10 was significantly higher in BD compared to HCs. Multiple linear regression analyses revealed that there were associations between cytokines, IL-1α, IL-1β, IL-6 and SERT availability in the midbrain but not in the thalamus, putamen and caudate. Furthermore, linear mixed effect analyses demonstrated that these associations were not different between HCs and BD.

CONCLUSION

While many cytokines have been proposed to be important in the pathophysiology of BD, our results demonstrated that significant associations between cytokines and SERT availability may explain the role of cytokines in mood regulation. However, these associations were not different between HCs and BD, which imply the role of these cytokines is not specific for BD.

Combination Therapy of Salvianolic Acid and Fluoxetine Improves the Cognitive Function of Rats with Chronic Stress-induced Depression

OBJECTIVE

To establish the beneficial effects of salvianolic acid and fluoxetine on the improvement of cognitive function and amelioration of depression-like symptoms of rats with chronic stress-induced depression.

METHODS

Ninety-nine male Sprague-Dawley rats were randomly divided into 5 groups--a control group with no stress challenge and 4 chronic stress groups. Rats assigned to chronic stress groups were exposed to stress for 3 weeks, and then were given placebo, fluoxetine (20 mg/kg), salvianolic acid (40 mg/kg), or combined fluoxetine and salvianolic acid. Body weight of each rat was recorded throughout the study. Sucrose preference test and water maze experiment were performed after chronic stress challenge and after drug treatment to assess the effect of drug treatments on depressive-like symptoms and cognitive function. The sucrose preference test was also performed before chronic stress exposure for baseline measurement.

RESULTS

Exposure of rats to chronic stress for 3 weeks significantly reduced body weight and sucrose preference values compared with the no stress control. The water maze experiment showed that chronic stress impaired the spatial learning of rats as well. Treatment of stress-challenged rats with fluoxetine and fluoxetine combined with salvianolic acid resulted in shorter training latency and longer time spent in the target quadrant during the exploration stage of the water maze experiment compared with placebo treatment. Effect of the combined regimen was found more obvious.

CONCLUSIONS

Combination therapy of salvianolic acid and fluoxetine could alleviate depression-like symptoms and cognitive deficit induced by chronic stress.

Allergic fetal priming leads to developmental, behavioral and neurobiological changes in mice

The state of the mother's immune system during pregnancy has an important role in fetal development and disruptions in the balance of this system are associated with a range of neurologic, neuropsychiatric and neurodevelopmental disorders. Epidemiological and clinical reports reveal various clues that suggest a possible association between developmental neuropsychiatric disorders and family history of immune system dysfunction. Over the past three decades, analogous increases have been reported in both the incidence of neurodevelopmental disorders and immune-related disorders, particularly allergy and asthma, raising the question of whether allergic asthma and characteristics of various neurodevelopmental disorders share common causal links. We used a mouse model of maternal allergic asthma to test this novel hypothesis that early fetal priming with an allergenic exposure during gestation produces behavioral deficits in offspring. Mothers were primed with an exposure to ovalbumin (OVA) before pregnancy, then exposed to either aerosolized OVA or vehicle during gestation. Both male and female mice born to mothers exposed to aerosolized OVA during gestation exhibited altered developmental trajectories in weight and length, decreased sociability and increased marble-burying behavior. Moreover, offspring of OVA-exposed mothers were observed to have increased serotonin transporter protein levels in the cortex. These data demonstrate that behavioral and neurobiological effects can be elicited following early fetal priming with maternal allergic asthma and provide support that maternal allergic asthma may, in some cases, be a contributing factor to neurodevelopmental disorders.

Toward a biosignature for suicide

OBJECTIVE

Suicide, a major cause of death worldwide, has distinct biological underpinnings. The authors review and synthesize the research literature on biomarkers of suicide, with the aim of using the findings of these studies to develop a coherent model for the biological diathesis for suicide.

METHOD

The authors examined studies covering a large range of neurobiological systems implicated in suicide. They provide succinct descriptions of each system to provide a context for interpreting the meaning of findings in suicide.

RESULTS

Several lines of evidence implicate dysregulation in stress response systems, especially the hypothalamic-pituitary-adrenal axis, as a diathesis for suicide. Additional findings related to neuroinflammatory indices, glutamatergic function, and neuronal plasticity at the cellular and circuitry level may reflect downstream effects of such dysregulation. Whether serotonergic abnormalities observed in individuals who have died by suicide are independent of stress response abnormalities is an unresolved question.

CONCLUSIONS

The most compelling biomarkers for suicide are linked to altered stress responses and their downstream effects, and to abnormalities in the serotonergic system. Studying these systems in parallel and in the same populations may elucidate the role of each and their interplay, possibly leading to identification of new treatment targets and biological predictors.

Dietary long chain n-3 polyunsaturated fatty acids prevent impaired social behaviour and normalize brain dopamine levels in food allergic mice

Allergy is suggested to exacerbate impaired behaviour in children with neurodevelopmental disorders. We have previously shown that food allergy impaired social behaviour in mice. Dietary fatty acid composition may affect both the immune and nervous system. The aim of this study was to assess the effect of n-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) on food allergy-induced impaired social behaviour and associated deficits in prefrontal dopamine (DA) in mice. Mice were fed either control or n-3 LCPUFA-enriched diet before and during sensitization with whey. Social behaviour, acute allergic skin response and serum immunoglobulins were assessed. Monoamine levels were measured in brain and intestine and fatty acid content in brain. N-3 LCPUFA prevented impaired social behaviour of allergic mice. Moreover, n-3 LCPUFA supplementation increased docosahexaenoic acid (DHA) incorporation into the brain and restored reduced levels of prefrontal DA and its metabolites 3,4-dihydroxyphenylacetic acid, 3-methoxytyramine and homovanillic acid in allergic mice. In addition to these brain effects, n-3 LCPUFA supplementation reduced the allergic skin response and restored decreased intestinal levels of serotonin metabolite 5-hydroxyindoleacetic acid in allergic mice. N-3 LCPUFA may have beneficial effects on food allergy-induced deficits in social behaviour, either indirectly by reducing the allergic response and restoring intestinal 5-HT signalling, or directly by DHA incorporation into neuronal membranes, affecting the DA system. Therefore, it is of interest to further investigate the relevance of food allergy-enhanced impairments in social behaviour in humans and the potential benefits of dietary n-3 LCPUFA supplementation.

Integrating the monoamine, neurotrophin and cytokine hypotheses of depression--a central role for the serotonin transporter?

Monoamine, in particular serotonergic neurotransmission has long been recognized as an important factor in the aetiology of depression. The serotonin transporter (SERT) is the primary regulator of serotonin levels in the brain and a key target for widely used antidepressant drugs, such as selective serotonin reuptake inhibitors (SSRIs). In realising the limitations of current antidepressant therapy, depression research has branched out to encompass other areas such as synaptic plasticity, neurogenesis and brain structural remodelling as factors which influence mood and behaviour. More recently, the immune system has been implicated in the development of depression and various intriguing observations have inspired the cytokine hypothesis of depression. Over the past two decades evidence of in vitro and in vivo regulation of SERT function by pro-inflammatory cytokines as well as by mechanisms of synaptic plasticity has been accumulating, offering a mechanistic link between the monoamine, neurotrophin and cytokine theories of depression. This review will focus firstly on the interconnected roles of serotonin and neurotrophins in depression and antidepressant therapy, secondly on the impact of the immune system on serotonin transporter regulation and neurotrophin signalling and finally we propose a model of reciprocal regulation of serotonin and neurotrophin signalling in the context of inflammation-induced depression.

Association of thalamic serotonin transporter and interleukin-10 in bipolar I disorder: a SPECT study

OBJECTIVES

The serotonin hypothesis plays a critical role in the etiology of bipolar disorder (BD). Although many studies have demonstrated reciprocal relationships between serotonin metabolism and immune-inflammatory pathways that occur in depression, studies linking serotonergic function and cytokines are still limited concerning BD. The aim of this study was to investigate the interaction of brain serotonin transporter (SERT) and cytokines in BD.

METHODS

Twenty patients with euthymic BD and 20 age- and sex-matched healthy controls (HC) were recruited. Single photon emission computed tomography with the radiotracer (123) I-ADAM was used for the SERT imaging. The specific uptake ratio, which represents SERT availability, was the primary measured outcome. Cytokines included the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) and the anti-inflammatory cytokine interleukin-10 (IL-10). Cytokine concentration was measured using an enzyme-linked immunosorbent assay.

RESULTS

SERT availability was significantly lower in the midbrain and caudate of patients with BD compared with HC, but not in the thalamus and putamen. IL-10 was significantly higher, whereas TNF-α was not different in euthymic patients with BD compared with HC. There was a significant association of SERT availability and IL-10 in the thalamus, but not in the midbrain, caudate, or putamen.

CONCLUSIONS

Our results demonstrate the interaction of SERT availability and IL-10 in euthymic BD. This result may further explain the role of SERT and cytokines in the etiology of BD.

A Preliminary Study on the Relationship between Platelet Serotonin Transporter Functionality, Depression, and Fatigue in Patients with Untreated Chronic Hepatitis C

Objective and Methods. Although the interaction between fatigue and depression in patients with chronic hepatitis C infection (HCV) has been recognized, the biological correlates of this observation have yet to be reported. We addressed this issue by examining serotonin transporter- (SERT-) driven [(14)C]-serotonin uptake rate (SUR) and serotonin content in platelets of 65 untreated HCV patients and 65 healthy control subjects (HCS). All patients completed report questionnaires for fatigue, depression, and general psychopathology. Structured interviews were conducted by a board-certified psychiatrist. Results. Whereas 36 of the patients experienced fatigue of moderate-to-severe intensity, only 16 reported symptoms of depression (BDI score > 10). Mean SUR in patients with depressive symptoms was significantly higher relative to the HCS, corresponding to a large Cohen's effect size of d = 1.45 (95% CI = 0.66-1.83). Patients who rated their fatigue to have a marked impact on mood and activity displayed a moderate relationship between the BDI score and SUR (n = 18, r = 0.563, P = 0.015), which becomes stronger after controlling for age, gender, and thrombocytopenia (r part = 0.710, P = 0.003). In the univariate analysis, high fatigue interference score, thrombocytopenia, and high SUR were all significant predictors of depression. Conclusions. High SERT activity could be implicated in the expression of depressive symptoms especially in a subgroup of HCV patients who are feeling fatigue as markedly distressing.

An intricate relationship between pain and depression: clinical correlates, coactivation factors and therapeutic targets

INTRODUCTION

An apparent clinical relationship between pain and depression has long been recognized, which makes an enormous impact on the individual health care. At present, the practical implication of such overlapping symptomatology between pain and depression is not clear, but the prevalence estimates for depression are substantially inflated among patients with chronic pain and vice versa. This interaction has been labeled as the depression-pain syndrome or depression-pain dyad.

AREAS COVERED

This article discusses the neurobiological substrates and neuroanatomical pathways involved in pain-depression dyad along with newer therapeutic targets.

EXPERT OPINION

Several key themes emerged from our review of the relationship between depression and pain. First, the diagnosis of depression in pain or vice versa is particularly challenging, and the development of better diagnostic framework that involves both pain and depression is particularly required. Secondly, the entwined relationship between pain and depression supports the possibility of common coactivating factors that results in their neurophysiological overlap. A broad understanding of the role played by the central nervous system (CNS) in the processing of pain and depression may eventually lead to the introduction of triple reuptake inhibitors, agomelatine, vilazodone and ketamine with novel mechanism of action, hence appear to be of promising potential for pain with depression.

The pro-inflammatory cytokine TNF-α regulates the activity and expression of the serotonin transporter (SERT) in astrocytes

Pro-inflammatory cytokines have been implicated in the precipitation of depression and related disorders, and the antidepressant sensitive serotonin transporter (SERT) may be a major target for immune regulation in these disorders. Here, we focus on astrocytes, a major class of immune competent cells in the brain, to examine the effects of pro-longed treatment with tumor necrosis factor-alpha (TNF-α) on SERT activity. We first established that high-affinity serotonin uptake into C6 glioma cells occurs through a SERT-dependent mechanism. Functional SERT expression is also confirmed for primary astrocytes. In both cell types, exposure to TNF-α resulted in a dose- and time-dependent increase in SERT-mediated 5-HT uptake, which was sustained for at least 48 h post-stimulation. Further analysis in primary astrocytes revealed that TNF-α enhanced the transport capacity (Vmax) of SERT-specific 5-HT uptake, suggesting enhanced transporter expression, consistent with our observation of an increase in SERT mRNA levels. We confirmed that in both, primary astrocytes and C6 glioma cells, treatment with TNF-α activates the p38 mitogen-activated protein kinase (MAPK) signaling pathway. Pre-treatment with the p38 MAPK inhibitor SB203580 attenuated the TNF-α mediated stimulation of 5-HT transport in both, C6 glioma and primary astrocytes. In summary, we show that SERT gene expression and activity in astrocytes is subject to regulation by TNF-α, an effect that is at least in part dependent on p38 MAPK activation.

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

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

Allergic rhinitis: an update on disease, present treatments and future prospects

Allergic rhinitis (AR) is an inflammation of nasal mucosa mediated by IgE-associated processes occurring independently, or concurrently with asthma. AR is characterized by sensitization-formation and expression of antigen specific IgE, followed by inflammation in two phases. The early phase response involves cross linking of IgE molecules leading to degranulation of mast cells and release of preformed mediators such as histamine and tryptase, or newly synthesized mediators such as prostaglandins and leukotrienes. The late phase response is predominated by the presence of eosinophils, lymphocytes, cytokines, and adhesion molecules. Newer insights reveal that the whole phenomenon of immunological inflammation is intricately knit with neural pathways, which strongly influence the process. Furthermore, AR can impact psychological health and vice versa. Classical pharmacotherapy of AR includes use of oral or topical antihistamines, oral antileukotrienes, topical corticosteroids, mast cell stabilizers, decongestants, and an anticholinergic agent. Among immunomodulatory treatments, immunotherapy is gaining widespread use, while antibody treatment is restricted mainly to resistant cases. Several small molecules with improved safety profile, or targeting novel mechanisms are in the clinical research. Newer antihistamines and corticosteroids with improved safety profile and antagonists of the prostaglandin D(2) (CRTH2) receptors are likely to be available for clinical use in the near future. Lack of properly validated animal models and complexities associated with clinical evaluation are some of the challenges facing the researchers in AR. Comprehensive understanding of immunological and neurological processes in AR would facilitate the future quest for more effective and safer management of this disease.

Gene-environment interactions in geriatric depression

In older adults, several environmental challenges can potentially trigger the onset of an episode of major depression. Vulnerability to these challenges can be influenced by genetics. There is accumulating evidence for an interaction between stress and a serotonin transporter polymorphism, though there is also heterogeneity among studies. Other relevant genes include those encoding for the neuroendocrine stress axis, growth factors, and other monoaminergic systems. Each of these may interact with either predisposing traumas in early childhood or precipitating events later in life.

Pathogenic factors involved in the development of irritable bowel syndrome: focus on a microbial role

Irritable bowel syndrome (IBS) is a symptom complex characterized by recurrent abdominal pain or discomfort, and accompanied by abnormal bowel habits, in the absence of any discernible organic abnormality. Its origin remains unclear, partly because multiple pathophysiologic mechanisms are likely to be involved. A significant proportion of patients develop IBS symptoms after an episode of gastrointestinal infection. In addition to gastrointestinal pathogens, recent evidence suggests that patients with IBS have abnormal composition and higher temporal instability of their intestinal microbiota. Because the intestinal microbiota is an important determinant of normal gut function and immunity, this instability may constitute an additional mechanism that leads to symptom generation and IBS. More importantly, a role for altered microbiota composition in IBS raises the possibility of therapeutic interventions through selective antibiotic or probiotic administration. The new concept of functional bowel diseases incorporates the bidirectional communication between the gut and the central nervous system (gut-brain axis), which may explain the multiple facets of IBS by linking emotional and cognitive centers of the brain with peripheral functioning of the gastrointestinal tract and vice versa.

Interleukin-1 receptor activation by systemic lipopolysaccharide induces behavioral despair linked to MAPK regulation of CNS serotonin transporters

Serotonin (5-hydroxytryptamine, 5-HT) has long been implicated in regulation of mood. Medications that block the neuronal 5-HT transporter (SERT) are used as major pharmacological treatment for mood disorders. Conversely, stimuli that enhance SERT activity might be predicted to diminish synaptic 5-HT availability and increase the risk for 5-HT-related CNS disorders. We have shown that the inflammatory cytokines enhance brain SERT activity in cultured serotonergic cells and nerve terminal preparations in vitro. In this study, we establish that intraperitoneal injection of the cytokine-inducer lipopolysaccharide (LPS) stimulates brain SERT activity, acting at doses below those required to induce overt motor suppression. SERT stimulation by LPS is paralleled by increased immobility in both the tail suspension test (TST) and the forced swim test (FST); antidepressant-sensitive alterations are thought to model aspects of behavioral despair. Both the stimulation of SERT activity and induced immobility are absent when LPS is administered to interleukin-1 receptor (IL-1R)-deficient mice and in the presence of SB203580, an inhibitor of IL-1R-stimulated p38 MAPK. Moreover, the ability of LPS to enhance immobility in TST is lost in SERT knockout mice. These findings reveal an ability of peripheral inflammatory stimuli to enhance brain SERT activity through IL-1R and p38 MAPK pathways in vivo and identify a requirement for SERT expression in immune-system-modulated despair behaviors. Our studies identify IL-1R- and p38 MAPK-dependent regulation of SERT as one of the mechanisms by which environmentally driven immune system activation can trigger despair-like behavior in an animal model, encouraging future analysis of the pathway for risk factors in neuropsychiatric disorders.

Gene variants predisposing to SIDS: current knowledge

Genetic risk factors play a role in sudden unexpected infant death; either as a cause of death, such as in cases with medium-chain acyl-coenzyme A dehydrogenase deficiency and cardiac arrest due to long QT syndrome, or as predisposing factors for sudden infant death syndrome (SIDS). Most likely genetic predisposition to SIDS represent a polygenic inheritance pattern leading to sudden death when combined with other risk factors, such as a vulnerable developmental stage of the central nervous system and/or the immune system, in addition to environmental risk factors, such as a common cold or prone sleeping position. Genes involved in the regulation of the immune system, cardiac function, the serotonergic network and brain function and development have so far emerged as the most important with respect to SIDS. The purpose of the present paper is to survey current knowledge on SIDS and possible genetic contributions.

Serotonin 5-HT(2A) Receptor Function as a Contributing Factor to Both Neuropsychiatric and Cardiovascular Diseases

There are high levels of comorbidity between neuropsychiatric and cardiovascular disorders. A key molecule central to both cognitive and cardiovascular function is the molecule serotonin. In the brain, serotonin modulates neuronal activity and is actively involved in mediating many cognitive functions and behaviors. In the periphery, serotonin is involved in vasoconstriction, inflammation, and cell growth, among other processes. It is hypothesized that one component of the serotonin system, the 5-HT(2A) receptor, is a common and contributing factor underlying aspects of the comorbidity between neuropsychiatric and cardiovascular disorders. Within the brain this receptor participates in processes such as cognition and working memory, been implicated in effective disorders such as schizophrenia, and mediate the primary effects of hallucinogenic drugs. In the periphery, 5-HT(2A) receptors have been linked to vasoconstriction and hypertension, and to inflammatory processes that can lead to atherosclerosis.

Fluoxetine treatment to rats modifies serotonin transporter and cAMP in lymphocytes, CD4+ and CD8+ subpopulations and interleukins 2 and 4

Several lines of evidences indicate that antidepressants produce various immunomodulatory effects. Fluoxetine, an antidepressant and selective serotonin reuptake inhibitor, modulates immune cells in vitro. To explore the in vivo influence of fluoxetine on lymphocytes, male Sprague-Dawley rats were treated daily, 10 mg/kg, or with saline solution for 1, 2 and 3 weeks. The presence of serotonin transporter in CD3+, CD4+ and CD8+ subpopulations of T lymphocytes was determined by immunofluorescence. Serotonin transporter was also labeled with [(3)H]paroxetine, specific binding defined with imipramine. Plasma levels of pro-inflammatory interleukin 2 (IL-2), and anti-inflammatory interleukin 4 (IL-4), were measured by ELISA; and cAMP concentration by radioimmunoassay. Fluoxetine significantly increased the number of lymphocytes expressing serotonin transporter and elevated the binding of [(3)H]paroxetine. The percentage of CD4+ cells decreased, that of CD8+ increased, and CD3+ did not change. The ratio CD4+/CD8+ was significantly lowered. Fluoxetine administration elevated the levels of IL-4 at 1, 2 and 3 weeks; and of IL-2, at 2 and 3 weeks. IL-4/IL-2 ratio was significantly increased in fluoxetine group respecting the controls and was similar during the 3 weeks of treatment. Fluoxetine produced a significant decrease in cAMP concentrations in lymphocytes, probably by secondary activation of serotonin receptors. Treatment with fluoxetine modified immune parameters in plasma and lymphocytes of rats, which might be relevant for its systemic therapeutic action as an antidepressant.

Physiological endpoints for potential SSRI interactions in fish

Selective serotonin reuptake inhibitors (SSRIs) are among the pharmaceutical compounds frequently detected in sewage treatment plant effluents and surface waters, albeit at very low concentrations, and have therefore become a focus of interest as environmental pollutants. These neuroactive drugs are primarily used in the treatment of depression but have also found broader use as medication for other neurological dysfunctions, consequently resulting in a steady increase of prescriptions worldwide. SSRIs, via inhibition of the serotonin (5-hydroxytryptamine, 5-HT) reuptake mechanism, induce an increase in extracellular 5-HT concentration within the central nervous system of mammals. The phylogenetically ancient and highly conserved neurotransmitter and neurohormone 5-HT has been found in invertebrates and vertebrates, although its specific physiological role and mode of action is unknown for many species. Consequently, it is difficult to assess the impact of chronic SSRI exposure in the environment, especially in the aquatic ecosystem. In view of this, the current knowledge of the functions of 5-HT in fish physiology is reviewed and, via comparison to the physiological role and function of 5-HT in mammals, a characterization of the potential impact of chronic SSRI exposure on fish is provided. Moreover, the insight on the physiological function of 5-HT strongly suggests that the experimental approaches currently used are inadequate if not entirely improper for routine environmental risk assessment of pharmaceuticals (e.g., SSRIs), as relevant endpoints are not assessed or impossible to determine.

Translational research in late-life mood disorders: implications for future intervention and prevention research

Clinical and epidemiological studies have consistently observed the heterogeneous symptomatology and course of geriatric depression. Given the importance of genetic and environmental risk factors, aging processes, neurodegenerative and cerebrovascular disease processes, and medical comorbidity, the integration of basic and clinical neuroscience research approaches is critical for the understanding of the variability in illness course, as well as the development of prevention and intervention strategies that are more effective. These considerations were the impetus for a workshop, sponsored by the Geriatrics Research Branch in the Division of Adult Translational Research and Treatment Development of the National Institute of Mental Health that was held on September 7-8, 2005. The primary goal of the workshop was to bring together investigators in geriatric psychiatry research with researchers in specific topic areas outside of geriatric mental health to identify priority areas to advance translational research in geriatric depression. As described in this report, the workshop focused on a discussion of the development and application of integrative approaches combining genetics and neuroimaging methods to understand such complex issues as treatment response variability, the role of medical comorbidity in depression, and the potential overlap between depression and dementia. Future directions for integrative research were identified. Understanding the nature of geriatric depression requires the application of translational research and interdisciplinary research approaches. Geriatric depression could serve as a model for translational research integrating basic and clinical neuroscience approaches that would have implications for the study of other neuropsychiatric disorders.

Expression of serotonin transporters by peripheral blood mononuclear cells of rhesus monkeys (Macaca mulatta)

It has been well established that serotonin (5-hydroxytryptamine, 5-HT) plays a key role in neuro-endocrine-immune networks, mostly through its receptors and/or transporters. Although the presence of 5-HT receptor mRNAs in peripheral blood mononuclear cells (PBMCs) of rhesus monkeys has been reported, there is little information about serotonin transporter (SERT) expression by these cells. To examine SERT expression at the transcription and translation level, one-step RT-PCR, confocal microscopy and flow cytometry were used to detect SERT mRNA and protein expression by rhesus monkey PBMCs. It was found that SERT mRNA could be detected by RT-PCR from all of the rhesus macaque PBMC RNA samples and the nucleotide sequence of the amplicons was identical to the published SERT mRNA sequence. Low level SERT immunoreactivity was also demonstrated on the surface of rhesus PBMCs by confocal microscopy. Almost all lymphocytes and most monocytes were positive for SERT by flow cytometry. In the 2 rhesus macaques examined by multicolor flow cytometry, SERT(bright) cells were more than 84%, 94%, and 96% among CD20+, CD3+, and CD3+CD4+ lymphocytes respectively. These data demonstrate expression of SERT by rhesus macaque PBMCs, and indicate that rhesus macaques would be suitable models to test the in vivo immune regulatory effects of 5-HT or drugs targeting SERT.

Cytokine imbalance in the pathophysiology of major depressive disorder

OBJECTIVE

A substantial body of evidence indicates that dysregulation of the immune system is associated with Major Depressive Disorder (MDD). Because most cytokines have pleiotropic effects, we measured various subsets of cytokines to examine the association between immune response and MDD.

METHODS

Forty-eight hospitalized MDD patients and 63 normal controls were recruited. We measured in vitro monocytic (IL-6 and tumor necrosis factor (TNF)-alpha), Th1 (interferon (IFN)-gamma and interleukin (IL)-2), Th2 (IL-4), and Treg (transforming growth factor (TGF)-beta1) cytokine production as well as IL-2/IL-4 and IFN-gamma/IL-4 ratios for both groups. Depressive symptoms were assessed by Hamilton Depression Rating Scale. Patients were evaluated before and after 6 weeks of antidepressant treatment.

RESULTS

At admission, IL-6, TNF-alpha, TGF-beta1 production, and IFN-gamma/IL-4 ratio were significantly higher, whereas IFN-gamma, IL-2, and IL-4 were significantly lower in MDD patients. After treatment, IL-6 and TGF-beta1 production were significantly lower than before treatment.

CONCLUSION

We suggest that activation of monocytic proinflammatory cytokines, and inhibition of both Th1 and Th2 cytokines may be associated with immunological dysregulation in MDD. TGF-beta1 may be associated with the regulation of monocytic cytokines as well as Th1 and Th2 cytokines in MDD.

The functional impact of SLC6 transporter genetic variation

Solute carrier 6 (SLC6) is a gene family of ion-coupled plasma membrane cotransporters, including transporters of neurotransmitters, amino acids, and osmolytes that mediate the movement of their substrates into cells to facilitate or regulate synaptic transmission, neurotransmitter recycling, metabolic function, and fluid homeostasis. Polymorphisms in transporter genes may influence expression and activity of transporters and contribute to behavior, traits, and disease. Determining the relationship between the monoamine transporters and complex psychiatric disorders has been a particular challenge that is being met by evolving approaches. Elucidating the functional consequences of and interactions among polymorphic sites is advancing our understanding of this relationship. Examining the influence of environmental influences, especially early-life events, has helped bridge the gap between genotype and phenotype. Refining phenotypes, through assessment of endophenotypes, specific behavioral tasks, medication response, and brain network properties has also improved detection of the impact of genetic variation on complex behavior and disease.

Cytokines and serotonin transporter in patients with major depression

Altered cytokine secretion as a mechanism in the etiology of depression is still obscure. The serotonin transporter (5-HTT) may play an important role in the termination of serotonergic neurotransmission by serotonin (5-HT) uptaking into presynaptic neurons and representing as an initial action site for selective 5-HTT reuptake inhibitors (SSRI). In our study, we evaluated whether cytokines and 5-HTT acted as biological markers for depression. Blood samples were collected from 42 participants. The differences in cytokine and 5-HTT mRNA expressions of leukocytes were assessed between the patients with major depression (n=20) and the healthy controls (n=22), along with the measurements prior and after treatment with a SSRI, fluoxetine, for 3 months in the follow-up patient group (n=8). The results revealed that the mRNA expressions of IL-1beta, IL-6, IFNgamma, TNFalpha, and 5-HTT were higher in the depressed patients than those of the healthy controls. The higher level of mRNA expressions of IFNgamma and 5-HTT diminished after fluoxetine treatment. Furthermore, we found a positive correlation between 5-HTT and cytokines mRNA expressions in total participants, which suggested that pro-inflammatory cytokines and 5-HTT might play critical roles in the pathogenesis of major depression and that their levels were affected by chronic treatment with 5-HTT inhibitors.

The rationale, efficacy and safety evidence for tegaserod in the treatment of irritable bowel syndrome

A growing body of evidence implicates abnormal serotonergic regulation of gastrointestinal function in the pathogenesis of the irritable bowel syndrome (IBS). Drugs targeting this system are therefore attractive concepts. The partial 5-HT4 receptor agonist tegaserod might be predicted to have positive therapeutic effects on a constipated and uncomfortable gut. However, IBS runs a chronic, benign course and carries no associated mortality, so it is imperative that the safety profile of new pharmacological agents made available to physicians is exemplary. The authors review the evidence for 5-HT in the aetiology of IBS and its symptoms, and the data available concerning the partial 5-HT4 receptor agonist tegaserod, in terms of rationale, efficacy and safety.

Hypothalamic-pituitary-gut axis dysregulation in irritable bowel syndrome: plasma cytokines as a potential biomarker?

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is a functional disorder with an etiology that has been linked to both psychological stress and infection. The primary aim of this study was to examine the hypothalamic-pituitary-adrenal axis in patients with IBS and to relate such response to plasma cytokine profiles.

METHODS

A total of 151 subjects, 76 patients and 75 controls, were recruited. The patients with IBS were diagnosed according to Rome II criteria. Forty-nine patients and 48 matched controls had cytokine levels measured, and a subset of 21 patients and 21 controls also underwent a corticotropin-releasing hormone (CRH) stimulation test with plasma levels of adrenocorticotropic hormone (ACTH) and cortisol measured. The remaining 27 patients and 27 controls underwent a dexamethasone (1 mg) challenge.

RESULTS

Cortisol and the proinflammatory cytokines interleukin (IL)-6 (together with its soluble receptor) and IL-8 were elevated in all IBS subgroups (diarrhea predominant, constipated, and alternators), although the elevation was most marked in the constipated subgroup. There was no alteration in the anti-inflammatory cytokine IL-10. Following CRH infusion, an exaggerated release of both ACTH and cortisol was observed in patients with IBS. There was a significant correlation between the ACTH response (deltaACTH) and the IL-6 levels. A similar relationship existed between the deltaACTH/deltacortisol ratio and the IL-6 levels. Dexamethasone suppression of cortisol was similar in patients and controls.

CONCLUSIONS

IBS is characterized by an overactivation of the hypothalamic-pituitary-adrenal axis and a proinflammatory cytokine increase.