Fluoxetine Treatment in Rats Increases the Rate of Taurine Transport in Mononuclear Cells.

Fluoxetine, a selective serotonin reuptake inhibitor antidepressant, modulates the mitogen-induced proliferation of lymphocytes. Lymphocytes contain taurine and express taurine transporter (TauT). Among the effects of taurine on lymphocytes are protection against oxidants and regulation of the inflammatory aspects of the immune response. Our aim was to determine the influence of fluoxetine treatment on taurine transport, and to determine the presence of TauT in the mononuclear cells of rats. METHODS: Male adult Sprague-Dawley rats were treated with fluoxetine 10 mg/kg i.p. for 1, 2, and 3 weeks. The cells were obtained by density gradients. [3H]Taurine was used for transport assays. Amino acid levels were determined by high-performance liquid chromatography. Immunolabeling of CD4+, CD8+, and TauT was performed. The mRNA of TauT was evaluated by RT-PCR. Controls were included for each protocol. RESULTS: The transport of taurine, after 1 week of treatment, was significantly augmented compared to controls. The affinity significantly increased at 1 and 2 weeks. While the percentage of CD4+ cells decreased and that of CD8+ cells increased, the percentage of TauT in CD4+ and CD8+ cells was not affected. Reduction of levels of aspartic acid, glutamic acid, threonine, alanine, glycine, and arginine occurred at 1 and 2 weeks. The taurine concentration significantly decreased after 2 and 3 weeks of treatment. The estimation of mRNA of TauT was not different. CONCLUSION: Taurine transport increases with fluoxetine treatment, and so this could be related to an immunomodulatory role of fluoxetine through TauT. Inhibition of serotonin reuptake might be involved in the regulation of taurine transport in mononuclear cells.

Zinc and zinc chelators modify taurine transport in rat retinal cells.

Zinc regulates Na(+)/Cl(-)-dependent transporters, similar to taurine one, such as those for dopamine, serotonin and norepinephrine. This study examined the ex vivo effect of zinc (ZnSO4), N,N,N,N-tetraquis-(2-piridilmetil)etilendiamino (TPEN) and diethylenetriaminepenta-acetic acid (DTPA), intracellular and extracellular zinc chelators, respectively, on rat retina [(3)H]taurine transport. Isolated cells were incubated in Locke solution with 100 nM of [(3)H]taurine for 25 s. Different concentrations of ZnSO4 (0.5-200 µM) were used. Low concentrations of ZnSO4 (30 and 40 µM) increased the transport, while higher concentrations (100, 150 and 200 µM) decreased it. Various concentrations of TPEN (1-200 µM) were added. Intermediate concentrations of TPEN (10-60 µM) significantly decreased [(3)H]taurine transport. The presence of TPEN, 20 µM, plus ZnSO4 reversed the effect of TPEN alone. Several concentrations of DTPA (1-500 µM) were also investigated. Reduction of transport took place at high concentrations of the chelator (100, 250 and 500 µM). DTPA, 500 µM, plus ZnSO4, did not modify the effect of it. These results indicate that zinc modulates taurine transport in a concentration-dependent manner, directly acting on the transporter or by forming taurine-zinc complexes in cell membranes.

5-HT7 receptors and tryptophan hydroxylase in lymphocytes of rats: mitogen activation, physical restraint or treatment with reserpine.

OBJECTIVES: Serotonin (5-HT)7 receptors in lymphocytes play a relevant role as modulators of T cell functions and might be modified by stress protocols. The aims of this work were to evaluate: (i) the presence of 5-HT7 receptors in specific lymphocyte populations, (ii) the probable modifications of them by inflammatory stress with mitogen and (iii) the effects of physical and pharmacological stress. METHODS: Blood lymphocytes were isolated by density gradients and differential adhesion to plastic. Concanavalin A (Con A) was systemically administered (500 µg/kg) or added to lymphocyte cultures (2.5 µg/ml, final volume 200 µl). Physical restraint was performed in Plexiglass boxes for 5 h per day for 5 days. Reserpine administration was 2.5 mg/kg for 3 days. Immunocytochemical labeling of CD4+, CD8+ and 5-HT7 receptors, and also tryptophan hydroxylase cells was performed. mRNA of 5-HT7 receptors was evaluated by RT-PCR. Controls were included for each protocol. RESULTS: Con A treatment or culture exposure increased the number of lymphocytes expressing 5-HT7 receptors or tryptophan hydroxylase, as compared to absence of the mitogen. Receptors were present in 12-16% of total rat lymphocytes, in ∼10% of CD4+ and in ∼5% of CD8+ cells from control rats. CD4+ decreased, and CD8+ and 5-HT7 cells increased after physical restraint. Reserpine treatment elevated CD8+ and 5-HT7 cells. Con A and physical restraint, but not reserpine treatment, significantly augmented 5-HT7 receptor mRNA in lymphocytes. CONCLUSIONS: Rat lymphocytes, expressing tryptophan hydroxylase, could synthesize 5-HT, functioning as a direct autocrine modulator. The modifications of CD4+, CD8+ and 5-HT7 receptors in lymphocytes by three stress protocols could have an impact on immune responses. In addition, the differential distribution of 5-HT7 receptors indicates potential specific physiopathological roles.

Serotonin transporter in lymphocytes of rats exposed to physical restraint stress.

OBJECTIVES: Glucocorticoids and stress cause transcriptional and functional changes on the serotonin transporter (SERT) in the central nervous system. Stress can produce specific modifications of SERT in lymphocytes, which could be associated with alterations in immune response. The aim of this study was to evaluate the effect of a physical restraint stress protocol on (1) rat lymphocyte proliferation in the presence of the selective serotonin reuptake inhibitor fluoxetine and (2) SERT kinetic parameters, i.e. binding capacity (Bmax), affinity (Kd) and Hill coefficient (nH). METHODS: Male adult Sprague-Dawley rats were placed in Plexiglass boxes (5 h daily for 5 days), and blood was obtained by cardiac puncture on day 6. Serum corticosterone was quantitated by an immunoenzymatic assay. Lymphocytes were isolated by density gradients and adhesion to plastic, of which there was sufficient material for further experiments, then cultured with or without the mitogen concanavalin A (Con A, 2 µg/ml) and fluoxetine (1-50 µM). Cell proliferation was measured with tetrazolium salts, and [(3)H]paroxetine was used as a SERT-specific ligand for binding assays. RESULTS: Restraint produced a significant increase in serum corticosterone of stressed rats. The proliferative response to Con A was similar in the controls and stressed animals. Fluoxetine reduced cell proliferation with and without Con A. Restraint diminished the inhibitory effect of fluoxetine on proliferation. Restraint also increased Bmax and Kd, but decreased nH. Treatment of rats with actinomycin D, a transcription inhibitor, reduced Bmax in stressed animals. CONCLUSIONS: Restraint stress modulated the effect of fluoxetine on cell proliferation, probably through the modification of the presence and the function of SERT.

Ácidos grasos omega-3 como coadyuvantes del tratamiento antidepresivo y sus efectos sobre el factor neurotrófico derivado del cerebro en suero y en células mononucleares / Omega-3 fatty acids as adjunctive of antidpressant therapy and its effects on brain-derived neurotrophic factor in serum, monocytes and lymphocytes

El estrés disminuye el factor neurotrófico derivado del cerebro (BDNF) en el hipocampo; los antidepresivos y los ácidos grasos omega-3 podrían aumentarlo. En pacientes con depresión mayor, investigamos la respuesta clínica a un antidepresivo solo o con ácido eicosapentanoico (EPA), y su influencia sobre los niveles de BDNF. Veinte pacientes se diagnósticaron según el DSM-IV-TR; evaluamos la respuesta con la Escala de Hamilton para Depresión (HAM-D). Los controles fueron 15 sujetos sanos. Los pacientes se distribuyeron en 2 grupos: uno recibió fluoxetina 20 mg/día y EPA 3.000 mg/día, y otro con fuoxetina 20 mg/día y placebo, durante 8 semanas. Se tomaron muestras de sangre en las semanas 0 y 8 para obtener suero, sin anticuoagulante, para medir los niveles de BDNF, y para aislamiento de células mononucleares, con heparina, para la localización inmunocitoquímica de BDNF. Diez pacientes no continuaron por diferentes causas. De los 10 restantes, 5 recibieron EPA y 5, placebo. El BDNF sérico disminuyó despúes de tratamiento en ambos grupos, más evidente en el grupo con EPA en el análisis pareado. El porcentaje de células mononucleares que expresaron BDNF fue inferior en los pacientes y aumentó después de los tratamientos. Por otra parte, las células con BDNF, las cuales estaban bajas en los deprimidos, aumentaron después de los tratamientos, lo que indica que en estás, el papel del tratamiento, especialmente con la combinación del antidepresivo y el ácido en cuestión, las modificaciones en el BDNF son más evidentes. A pesar de la limitante que constituye la inclusión de los sujetos diagnósticados, más la permanencia de los incluidos, los resultados significativos señalan un efecto beneficiosos del uso de EPA en la depresión mayor

Stress is associated with a decreased expression of brainderived neurotrophic factor (BDNF) in the hippocampus. Antidepressants and omega-3 fatty acids might increase circulating BDNF. This research was done to evaluate, in major depression patients, the possible differences in clinical response to an antidepressant alone or in combination with eicosapentaenoic acid (EPA), and their influence on BDNF levels. Nineteen patients were diagnosed according to DSM-IV-TR criteria; severity and response was evaluated by Hamilton Depression Rating Scale (HAM-D). Control group was composed of 15 healthy subjects. Patients were randomized on a double-blind bassis in two groups: one recived fluoxetine 20 mg/day and EPA 3,000 mg/day, and the other one fluoxetine 20 mg/day an placebo, during 8 weeks. Blood samples were taken for obtaining serum and for isolating monocytes and lymphocytes at weeks 0 and 8. Ten patients dropped out for different causes. Of the remaining 9 subjetcs, 4 recived EPA and 5 got placebo. The percentage of mononuclear cells expressing BDNF was lower in patients, and it was significantly increased after the treatments. EPA seems to augment the clinical response. In depressed, after treatment, there was a lower content of serum BDNF. Moreover, mononuclear cells with BDNF, which were lower in this group of depressed, increased after the treatments, indicating that in cells the modulation of BDNF by antidepressants is more evident

Effects of zinc ex vivo on taurine uptake in goldfish retinal cells.

BACKGROUND: Taurine and zinc exert neurotrophic effects in the central nervous system. Current studies demonstrate that Na+/Cl- dependent neurotransmitter transporters, similar to that of taurine, are modulated by micromolar concentrations of zinc. This study examined the effect of zinc sulfate ex vivo on [3H]taurine transport in goldfish retina. METHODS: Isolated cells were incubated in Ringer with zinc (0.1-100 microM). Taurine transport was done with 50 nM [3H]taurine or by isotopic dilution with taurine (0.001-1 mM) and 50 nM [3H]taurine. RESULTS: Zinc reduced the capacity of taurine transport without changes in affinity, and caused a noncompetitive inhibition of high affinity taurine transport, with an EC50= 0.072 microM. The mechanism by which zinc affects taurine transport is unknown at the present. CONCLUSIONS: There may be a binding site of zinc in the transporter that affects union or translocation of taurine, or possibly the formation of taurine-zinc complexes, rather than free zinc, could affect the operation of the transporter.

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.

Effect of folic acid combined with fluoxetine in patients with major depression on plasma homocysteine and vitamin B12, and serotonin levels in lymphocytes.

OBJECTIVE(S): Folic acid, a micronutrient supporting the natural defense system, may elevate antidepressant responses, although the lymphocyte serotonergic system has not been explored in folate-supplemented depressed patients. METHODS: Twenty-seven patients were randomly assigned to groups receiving fluoxetine (20 mg) and folic acid (10 mg/day) or fluoxetine and placebo for 6 weeks. Clinical outcome was assessed according to the Hamilton Depression Rating Scale (HDRS) at the beginning, during and at the end of treatment. Blood samples were taken, plasma was separated, and lymphocytes were obtained by density gradient centrifugation with Ficoll/Hypaque and differential adhesion to plastic dishes. Fifteen healthy subjects served as controls. Plasma folate, homocysteine and vitamin B12, and serotonin concentration in lymphocytes were determined by HPLC. The HDRS score was significantly lower in patients receiving fluoxetine and folic acid compared with those receiving fluoxetine and placebo after 6 weeks of treatment (7.43 +/- 1.65 vs. 11.43 +/- 1.31, respectively; p = 0.04). Plasma homocysteine statistically significant decreased after folic acid (p = 0.02), but no significant changes were observed in vitamin B12. RESULTS: Serotonin was significantly reduced after fluoxetine either with folate (p = 0.03) or placebo (p = 0.01) probably by the effect of transporter blockade. 5-Hydroxyindoleacetic acid was lower in lymphocytes of patients receiving folate (p = 0.04), indicating a reduced turnover rate, thus accumulating serotonin in the cells. A significant negative correlation was noted between homocysteine and folate. No significant correlations were present among biochemical parameters and depression severity. CONCLUSION: Modifications due to treatment with fluoxetine and folic acid may alter lymphocyte function in depression probably indirectly by reducing homocysteine levels and directly on lymphocytes by modifying the serotonergic system.

Serotonin transporter is differentially localized in subpopulations of lymphocytes of major depression patients. Effect of fluoxetine on proliferation.

Modifications of lymphocyte serotonergic system have been described in major depression. The aim of this study was to determine new possible changes of this system in depression. Twenty eight patients, free of drugs, diagnosed with major depression disorder by Structured Clinical Interview for Disorders of Axis I, without medical illnesses, written consent, approved by Ethical Committees were included. Controls were 30 healthy subjects without family history of psychiatric disease. Blood monocytes were isolated with Ficoll/Hypaque, and lymphocytes by differential adhesion to plastic. Serotonin and 5-hydroxyindoleacetic acid determined by HPLC. Monocytes had higher serotonin concentrations than lymphocytes, and serotonin/5-hydroxyindoleacetic acid was lower in patients. Basal proliferation was elevated in depressed and not increased by Concanavalin A. Fluoxetine reduced basal proliferation more efficiently in patients, indicating activation of lymphocytes in depression. The number of cells expressing serotonin transporter was reduced in depressed. There were no differences in CD4+ (approximately 50%) or CD8+ (approximately 25%) lymphocytes between the groups, although CD8+ were lower in depressed, and greater number of them co-localized serotonin transporter than CD4+, which could be crucial for function in relation to serotonin and its receptors in immune cells. Lymphocytes were activated in this group of patients and fluoxetine reduced proliferation, probably being relevant for the psychopharmacological treatment of depression.

Síntesis de serotonina y presencia de hidroxilasa de triptófano en linfocitos de pacientes con depresión mayor tratados con fluoxetina y ácido fólico / Synthesis of serotonin and tryptophan hydroxylase in lymphocytes from patients with major depression treated with fluoxetine and folic acid

El ácido fólico ha sido utilizado como coadyuvante antidepresivo, y se han reportado bajos niveles séricos en deprimidos. Debido al papel del ácido fólico y a la relevancia del sistema serotonérgico linfocitario en la depresión, el objetivo de este estudio es determinar la capacidad de producción de serotonina y la presencia de la hidroxilasa del triptófano en linfocitos de pacientes deprimidos tratados con fluoxetina y ácido fólico. Los pacientes fueron diagnosticados con los criterios del Manual Diagnóstico y Estadístico de la Asociación Psiquiátrica Americana, la intensidad del episodio depresivo se determinó mediante la Escala de Hamilton para Depresión. Veintisiete pacientes (21-58 años) fueron seleccionados, no presentaban otra patología ni riesgo suicida. Se distribuyeron en forma aleatoria en dos grupos experimentales, unos (14) recibieron fluoxetina, 20 mg/d, más ácido fólico, 10 mg/d y otros (13) fluoxetina más placebo. El grupo control fue constituido por 15 sujetos aparentemente sanos (26-49 años). Se tomaron muestras de sangre al principio y después de seis semanas. Diez pacientes de cada grupo experimental culminaron el estudio. La homocisteína plasmática disminuyó con la administración de ácido fólico. Los linfocitos fueron aislados por gradientes de densidades con Ficoll/Hypaque y adhesión diferencial al plástico. Las concentraciones de serotonina en linfocitos se determinaron por cromatografía líquida de alta resolución con detector electroquímico y no difirieron entre los dos grupos ni en relación al control, pero fueron bajas en los que recibieron el tratamiento. La síntesis de serotonina a partir de triptófano fue menor en los pacientes en relación a controles, y disminuyó después de los dos tratamientos. El número de linfocitos con la enzima fue menor en los pacientes y decreció después del ácido fólico.

Taurine transport and transporter localization in peripheral blood lymphocytes of controls and major depression patients.

Taurine concentration is increased in peripheral blood lymphocytes in a group of depressed subjects. After this observation [3H]taurine transport was measured in lymphocytes of 10 major depression patients (19-60 years old), diagnosed by the criteria of the American Psychiatric Association, with moderate severity as determined by Hamilton Scale for Depression (32 +/- 6). The control group comprised 10 subjects (20-56 years old). Taurine transporter and CD4+ (helpers) and CD8+ (cytolytic) T lymphocytes were immunolabeled. No significant differences were observed in immunochemical analyses. CD4+ cells were 53% and CD8+ cells 28% of the total lymphocytes in both controls and patients. Two taurine transport components, high and low affinity, were demonstrated in both groups. Taurine transporter was present in 16% of CD4+ and CD8+ lymphocytes in controls and patients. This preliminary report exhibits the presence of taurine transporter in peripheral blood lymphocytes but no differences were observed between controls and depressed subjects.

Effect of mirtazapine treatment on serotonin transporter in blood peripheral lymphocytes of major depression patients.

Lymphocytes from human peripheral blood exhibit a series of markers of neurotransmitters, such as specific receptors and transporters. A reduction of serotonin transporters and an increase of them has been reported after treatment with fluoxetine in depressed patients. The aim of this study was to determine if the administration of an antidepressant with a different mechanism of action, such as mirtazapine, could produce a similar effect. Twenty eight patients (age 41.40+/-2.45) were diagnosed following the criteria for major depression by the Structured Clinical Interview for Disorders of Axis I of the American Psychiatric Association. Severity was measured by Hamilton Scale and by Beck Inventory for Depression, scores of 30.88+/-7.48 and 30.24+/-10.88, respectively, prior to treatment. Samples from control subjects were obtained alternating with patients before and after the administration of the antidepressant: twenty eight and twenty four, respectively (age 38.80+/-2.95). Mirtazapine was given in a dose of 30 mg/day for 6 weeks. Blood lymphocytes were isolated by density gradient from patients and controls before and after treatment. There was a partial response according to clinical evaluation and scores of the Scale and the Inventory. Serotonin transporters were labeled with [3H] paroxetine. Number of sites (B(max)) were 10.86+/-2.60 and 12.58+/-2.71 fmol/10(6) cells for both groups of controls. The depressed patients had a significant reduction of serotonin transporters in their lymphocytes before treatment and an increase after it, with B(max) values of 6.52+/-0.49 and 15.61+/-0.49 fmol/10(6) cells, respectively. There were no significant differences in the affinity for the ligand. Concentrations of serotonin or noradrenaline in lymphocytes were not modified before the treatment, although there was a significant decrease after taking 30 mg/day of the antidepressant for 6 weeks. Mirtazapine, not being a serotonin reuptake inhibitor, did increase the number of transporters in lymphocytes of major depression patients, indicating a complex mechanism, not only directly related to the transporter, but involved in the therapeutic response.

Characterization of serotonin transporter in blood lymphocytes of rats. Modulation by in vivo administration of mitogens.

Serotonin transporter sites were characterized in blood lymphocytes of rats. Pharmacological characteristics of drug interactions were in concordance with recent studies in nervous and human immune cells. The potency order of inhibition of [(3)H]paroxetine binding was imipramine>citalopram>alaproclate>serotonin. Selective inhibitors of dopamine or noradrenaline transporters did not inhibit it. The specific binding of [(3)H]paroxetine was higher at intermediate than at low concentrations, and the plot of free vs. specific binding had a sigmoid shape. The affinity constant or K(d), 1.77 nM, was in close agreement with data obtained from kinetic studies (K(d)=1.33 nM), which evidences that the equilibrium was reached. In addition, serotonin transporter was evaluated by lipopolysaccharide or concanavalin A administration in vivo (0.1 mg/kg, i.p., 18 h). After the treatment with lipopolysaccharide, no changes were observed in the numbers of sites or B(max) or in the affinity, K(d). The treatment with concanavalin A showed a significant reduction in B(max) and reduction in K(d). Additionally, serotonin and 5-hydroxyindoleacetic acid levels were determined in plasma and lymphocytes by high-performance liquid chromatography. Treatment with lipopolysaccharide produced a significant increased of serotonin levels in lymphocytes without changes in 5-hydroxyindoleacetic acid level; in plasma, it produced an increase in serotonin and 5-hydroxyindolacetic acid levels. In addition, serotonin synthesis was evaluated by adding 300 microM of tryptophan in the medium, which significantly increased serotonin levels in control lymphocytes. Moreover, the concentrations of 5-hydroxyindoleacetic acid was enhanced significantly, both in plasma and lymphocytes in the presence of tryptophan after treatment with lipopolysaccharide. The administration of concanavalin A significantly decreased plasma levels of serotonin, as well as the concentrations of serotonin and 5-hydroxyindoleacetic acid in lymphocytes. These results demonstrate the presence of serotonin transporter in lymphocytes of rat blood, the capacity for serotonin synthesis in lymphocytes, and the modulation of these parameters by systemic administration of mitogens. The findings of this work contribute to understanding the immunological role of serotonin and the communication of immune and nervous systems.

5-HT1A and beta-adrenergic receptors regulate proliferation of rat blood lymphocytes.

Lymphocytes possess serotonin 5-HT(1A) and beta-adrenergic receptors, which have been related to cell proliferation. In the present report, lymphocytes of rat blood were isolated by Ficoll-Hypaque gradients and differential adhesion to plastic. They were cultured in RPMI medium for 72 h in the presence of the mitogens lipopolysaccharide concanavalin A and anti-CD3 antibody. The latter two stimulated the proliferation of lymphocytes, but not the first. Serotonin (0.1-100 microM) was added alone or in the presence of suboptimal concentrations of concanavalin A (2 microg/ml) or anti-CD3 antibody (0.4 microg/ml). The 5-HT(1A) receptor agonists, 8-hydroxy-2-(di-n-propylamino)tetralin and buspirone (0.1-100 microM) were also tested in the cultures. Serotonin, 8-hydroxy-2-(di-n-propylamino)tetralin and buspirone neither had any effect by themselves, nor modified the proliferation induced by the mitogens. Noradrenaline (25-1,000 microM) and the beta-adrenergic receptor agonist, isoproterenol (5-100 microM), produced a reduction of the activation induced by concanavalin A or anti-CD3 antibody in a dose-dependent manner. Increasing serotonin concentrations reduced the inhibitory effect of noradrenaline (300 microM). Variable concentrations of 8-hydroxy-2-(di-n-propylamino)tetralin or buspirone also reduced the inhibition produced by isoproterenol (100 microM). The antagonist of 5-HT(1A) receptors, WAY-100,478 (0.1-100 microM), inhibited concanavalin A- or anti-CD3 antibody-induced proliferation. Serotonin (0.1-100 microM) impaired the inhibitory effect of the 5-HT(1A) antagonist (10 microM). The inhibitor of tryptophan hydroxylase, p-chlorophenylalanine (50-1,000 microM), decreased the stimulatory effect of concanavalin A, serotonin (0.5-100 microM) and 8-hydroxy-2-(di-n-propylamino)tetralin (1-100 microM) reverted the effect of p-chlorophenylalanine (1,000 microM). The serotonin reuptake blockers zimelidine, imipramine and clomipramine decreased concanavalin A-induced proliferation. The concentrations of serotonin and noradrenaline increased in lymphocytes cultured in the presence of concanavalin A, probably as a mechanism for modifying the final effect on proliferation. The present results indicate that 5-HT(1A) receptors play a stimulatory role on rat blood lymphocytes, and they interact in a parallel and opposite manner with beta-adrenergic receptors. Furthermore, endogenous serotonin is relevant in displaying its stimulatory effect.

Taurine concentration in human blood peripheral lymphocytes: major depression and treatment with the antidepressant mirtazapine.

Major depression is a serious disease with various systemic effects, including dysfunction of the immune response. Taurine has been known to be related to certain modifications of the immune system. The aim of this study was to determine the taurine concentration in lymphocytes of patients with major depression and to evaluate the influence of the antidepressant treatment with mirtazapine for six weeks on the levels of taurine. Gamma-aminobutyric acid, aspartate, glutamate and glutamine were also determined. Taurine, aspartate and glutamine levels were increased in the lymphocytes of depressed patients before mirtazapine treatment compared to the control group, and were normalized after treatment. Gamma-aminobutyric acid and glutamate did not differ between patients and controls. There was a significant and positive correlation between the severity of the disorder, measured by the Hamilton Rating Scale, and the concentration of taurine in the lymphocytes of depressed patients before treatment. This correlation was not observed after treatment and neither was there a correlation observed for the other amino acids. The present observations could be an indication of the relevance of taurine as a protective agent in the lymphocytes of patients with severe depression, and could be the result of modifications of taurine transport or efflux processes.

8-[3H]-hydroxy-2-(di-n-propylamino)tetralin binding sites in blood lymphocytes of rats and the modulation by mitogens and immobilization.

Serotonin 5-HT(1A) receptors were characterized in rat resting lymphocytes obtained by cardiac puncture with the use of the ligand [3H]8-hydroxy-2-(di-n-propylamino)tetralin. Selectivity of the specific binding was demonstrated by inhibition experiments with various serotonergic and nonserotonergic drugs. The rank order of potency for inhibition was WAY-100478>pindobind>NAN-190>buspirone>imipramine>serotonin. While pimozide, desipramine, nomifensine, haloperidol and sulpiride did not inhibit the binding. Kinetic parameters calculated from saturation experiments indicated one site of interaction, with an equilibrium dissociation constant of 2.50 nM and maximum binding capacity of 487.21 nmol/10(6) cells. Complete dissociation was obtained with serotonin as the displacement agent, and equilibrium dissociation constant calculated by association and dissociation experiments was 2.03 nM. Thus, serotonin 5-HT(1A) receptors are present in resting lymphocytes. The in vivo administration of the mitogens lipopolysacharide (0.1 mg/kg, 18 h) or concanavalin A (0.2 mg/kg, 18 h) increased the number of sites. The elevation produced by the latter was of higher magnitude than that of lipopolysacharide, and two sites of the binding were determined by isotopic dilution. Immobilization stress (1 h daily for 7 days) also resulted in a significant increase of binding capacity, but was smaller than that produced by the mitogens. The affinity of binding was not affect by the treatments. The results indicate that serotonin 5-HT(1A) receptors are modulated by unspecific and specific immune system activation, as well as by a potent stress condition, which might result in relevant functional modifications in the response of rat lymphocytes.

Serotonin transporter modulation in blood lymphocytes from patients with major depression.

1. Serotonin is a neurotransmitter in the central nervous system which has been implicated in the aetiology and pathogenesis of affective disorders. The serononergic system also plays several roles in the immune system through the expression of a number of its receptor subtypes in the immune cells. 2. Following release serotonin is inactivated by reuptake into neurons and other cells by a specific serotonin sodium and chloride-dependent transporter molecule, whose structure has been elucidated. 3. Measurement [3H]paroxetine binding showed that human lymphocytes contain a high-affinity serotonin transporter. 4. To assess the serotonin function in major depression, we investigated serotonin transporter density in blood lymphocytes from patients with this disorder and selected according to the interview of the American Psychiatric Association. 5. Patients were divided into two groups and treated with two different antidepressant drugs, one group receiving fluoxetine, a selective serotonin reuptake inhibitor, and another mirtazapine, an antagonist of alpha2-adrenergic auto and heteroreceptors, for a period of 6 weeks. 6. Blood samples were obtained before and after the treatment, lymphocytes were isolated by Ficoll/Hypaque gradient, subjected to differential adhesion to plastic, and cell membranes were prepared for binding assay of [3H]paroxetine. 7. Lymphocytes serotonin transporter number was significantly reduced, while the affinity was unchanged, in patients with major depression disorder as compare to controls. 8. In addition, there was a partial recovery in lymphocytes serotonin (5HT) transporter number in the period posterior to the antidepressants administration, accompanied with clinical and depression rating scales improvement. Serotonin was determined in platelet-poor plasma and in lymphocytes before and after drugs administration, showing a significant decrease in the patients treated compared to untreated and controls. 9. These results are evidence of the potential interaction between the nervous and immune systems. The mechanisms underlying this interaction are under study, and might be related to modifications in the expression or function of the serotonin transporters in lymphocytes of depressed patients.

Incriase of the serotonin metabolite, 5-hydroxyindoleacetic acid, in cerebro-spinal fluid and spinal cord of bovines affected with the paraplegic syndrome

The paraplegic syndrome of bovines is a condition characterized by impairment of locomotion, hypoalgesia and finally death within 72 h. The pathogenesis of the syndrome has not been established. In the present work we determined the levels of monoamines and their metabolites in cerebro-spinal fluid and spinal cord of affected animals in order to investigate the functional state of these neurotransmitters. The content of the main metabolite of serotonin, 5-hydroxyindoleacetic acid, was elevated in the cerebro-spinal fluid and in the gray matter of the spinal cord of paraplegic bovines. Serotonin content in the spinal cord did not differ with respect to control animals, but was decreased in the cerebro-spinal fluid of affected animals. Modifications in the noradrenergic system were also observed, but were less consistent, for which reason further studies are needed. These observations indicate an increase in the turnover rate of serotonin in the paraplegic syndrome. The meaning of the described alterations is unknown at the moment