Michèle Schwald

Decreased serum brain-derived neurotrophic factor levels in major depressed patients.

Recent findings with animal models have suggested a possible role for brain-derived neurotrophic factor (BDNF) in depression. We have therefore hypothesized that depression could be characterized by low levels of serum BDNF. Major depressed patients (15F + 15M) diagnosed according to DSM-IV criteria and healthy controls (15F + 15M) participated in the study. Serum BDNF was assayed with the ELISA method and the severity of depression was evaluated with Montgomery-Asberg-Depression Rating Scale (MADRS). BDNF levels were significantly lower in patients than in controls: 22.6 +/- 3 and 26.5 +/- 7 ng/ml (t-test = 2.7; d.f. = 58; P < 0.01). They were negatively correlated to the MADRS scores (r = -0.55; P < 0.02). Female patients were more depressed and released less BDNF than men. Analysis of covariance (MADRS and gender as independent variable vs. BDNF as dependent variable) indicated that depression severity mainly accounted for the negative correlation. These results suggest that major depression is characterized by low serum BDNF levels and support the hypothesis of neurotrophic factor involvement in affective disorders.

Postnatal developmental profile of brain-derived neurotrophic factor in rat brain and platelets

The brain-derived neurotrophic factor (BDNF) has been involved in pre- and postnatal brain development. Moreover, abundant levels of this neurotrophin have been found in animal and human brain and serum. This study was aimed to assess the postnatal change profile of both serum and brain BDNF levels. By using immunoassay and reverse transcription-polymerase chain reaction methods, BDNF protein and mRNA levels were determined in serum and platelets, respectively, and in two brain structures (hippocampus and frontal cortex) of postnatal rats (one and three weeks old), young adults (two months old) and in aged animals (two years old). The results showed that brain and serum BDNF levels underwent similar changes during maturation and aging processes (analysis of variance (ANOVA): P<0.001, P<0.001, for hippocampus and serum, respectively). During the same investigation period, the measure of BDNF mRNA indicated gradual changes in the hippocampus but not in platelets (ANOVA: P<0.001 and not significant, for hippocampus and platelets, respectively). Interestingly, there was a positive correlation between serum and cortical BDNF levels (r=0.81, P<0.01), especially in young animals. This study of ontogenic characteristics of BDNF in blood and central nervous system can help to shed more light on the role of platelet BDNF.

Low brain-derived neurotrophic factor (BDNF) levels in serum of depressed patients probably results from lowered platelet BDNF release unrelated to platelet reactivity.

BACKGROUND Recent reports have suggested a role for brain-derived neurotrophic factor (BDNF) in psychiatric disorders. Decreased serum BDNF levels have been reported in major depression, but the cause of this decrease has not yet been investigated. The goal of this study was to assess blood BDNF and a platelet activation index, PF4. METHODS Forty-three drug-free patients (27 female, 16 male) diagnosed with major depression and 35 healthy control subjects (18 female, 17 male) were assessed for plasma, serum, and blood BDNF content. Brain-derived neurotrophic factor and PF4 were assayed with enzyme-linked immunosorbent assay methods, and severity of depression was evaluated with the Montgomery-Asberg Depression Rating Scale. RESULTS Serum and plasma BDNF levels were decreased in depressed patients compared with control subjects. In whole blood, BDNF levels were unaltered in the depressed subjects compared with control subjects. The serum/blood BDNF ratio was lower in patients with major depression. Increased plasma but not serum PF4 levels were observed in depressed subjects compared with control subjects. CONCLUSIONS Our results suggest that an alteration of serum or plasma BDNF is not due to the change in blood BDNF but rather is probably related to mechanisms of BDNF release. Secretion of BDNF seems to be independent of platelet reactivity; other mechanisms are therefore probably involved and need to be elucidated.

Partial normalization of serum brain-derived neurotrophic factor in remitted patients after a major depressive episode.

We had previously reported decreased serum brain-derived neurotrophic factor (BDNF) levels in depressed patients. In the present study, we tested the hypothesis that antidepressant treatment would normalize serum BDNF levels, at least in a subgroup of patients. Major depressed patients (15 females and 11 males) diagnosed according to DSM-IV criteria and healthy controls (13 females and 13 males) participated in this study. Serum BDNF was assayed with the ELISA method for depressed and remitted patients and the severity of depression was evaluated with the Montgomery-Asberg Depression Rating Scale. An analysis of variance showed that treatment had an effect [F(1, 24) = 4.46, p = 0.045] on the normalization of serum BDNF levels. We also found a correlation between the severity of depression (r = 0.51, p = 0.008), the pretreatment BDNF levels (r = 0.62, p = 0.001) and the difference in serum BDNF levels after antidepressant treatment. These results suggest that antidepressant treatment has a positive effect on serum BDNF levels and support the hypothesis of neurotrophic factor involvement in affective disorders.

Early effects of mood stabilizers on the Akt/GSK-3β signaling pathway and on cell survival and proliferation

RationaleLithium, some of the anticonvulsants, and several second-generation antipsychotic drugs are common medications widely prescribed to treat bipolar disorder. Molecular targets and cellular events that mediate their effects have been described for these drugs but are only partially unraveled. Few comparative studies have been performed.ObjectivesWe evaluated seven mood stabilizers (MS) in the same in vitro system and found several differences and similarities in their cellular mechanisms (proliferation and cell survival). As some MS were previously shown to activate the Akt/GSK-3β axis, this pathway was explored for other drugs.Materials and methodsThe SH-SY5Y cells were cultured in RPMI-1640 medium. Effects of MS drugs on serum-induced cell proliferation and on slowing of cell death were analyzed. Phosphorylation and expression of Akt-1 and GSK-3β mRNA and protein were assessed for the seven drugs as well.ResultsLithium, Valproate, Olanzapine, and Clozapine enhance proliferation and protect cells against serum withdrawal-induced injury. These drugs also activate Akt-1 and GSK-3β phosphorylation. Interestingly, gene expression of Akt-1 mRNA and protein, but not GSK-3β, was increased. The other drugs Lamotrigine, Haloperidol, and Carbamazepine did not affect cellular events nor activate Akt/GSK-3β axis.ConclusionValproate and atypical antipsychotics (Olanzapine and Clozapine) regulate SH-SY5Y cell proliferation and survival, activate the Akt/GSK-3β axis, and stimulate gene expression of Akt-1 mRNA and protein, as does Lithium. The other medications have no effect. The study shows the importance of the Akt/GSK-3 axis in MS actions but also pinpoints a different dependence of these drugs on this signaling axis.

A non-radioactive assay for the cAMP-dependent protein kinase activity in rat brain homogenates and age-related changes in hippocampus and cortex

Cyclic AMP-dependent protein kinase (PKA) activity was involved in a number of brain functions such as cognitive process or aging. The measurement of PKA activity is traditionally based on the use of [(32)P]ATP in phosphorylation of specific protein. Recently non-isotopic PKA assays have been developed, but none has been tested on brain homogenates. This work aimed to adapt a fluorimetric method of PKA activity into a novel assay never applied before in brain homogenate, and to characterize the enzyme activity and ratio in hippocampus and cortex from rats of different ages. Optimal conditions of homogenization and enzyme protection were determined. The method was sensitive and reproducible (intra-assay and interassay variation was 5.0% and 9.0%, respectively). In hippocampal cytosol, PKA activity was 27+/-8 and 80+/-9 nmol/min per mg protein in basal and cAMP-stimulated activity, respectively, and accounted for 80% of total cell PKA activity. The non-PKA activity, assessed by the use of the PKA specific inhibitor (PKI) accounted for 49.0% and 65.0% of endogenous levels in cytosol and membrane, respectively. cAMP-augmenting drugs effects were measured and increase of 53%, 273% and 118% over basal by 10 microM isoproterenol, 100 microM forskolin, 1 microM Sp-AMP, respectively, was observed. With respect to the changes in animal age, PKA activity increased from newborn to the mature rats but decreased in older rats. The PKA ratio was higher in cytosol than in particulate fraction, and was decreased in hippocampal sample from old rats (P<0.05). This last result was interpreted as related to the loss of cognitive capacities in old animals.

The cAMP-dependent protein kinase A and brain-derived neurotrophic factor expression in lymphoblast cells of bipolar affective disorder

BACKGROUND Abnormalities in cAMP signaling and altered expression of downstream targets such as brain-derived neurotrophic factor (BDNF) have been postulated in patients with bipolar disorder (BD). METHODS The PKA activity and levels of (3)H-cAMP binding to PKA R regulatory subunits were measured in lymphoblasts from 10 BD and 10 control subjects. In addition, the possibility that BDNF expression could be altered in these cells has been explored. RESULTS Results indicate that PKA activity significantly increased (t-test; P<0.01), whereas the (3)H-cAMP binding to PKA R subunits decreased in cells from BD (t-test; P<0.02). The presence of 10 microM Sp-cAMP in culture 24 h before cell harvesting induced an increase in enzyme activity and a decrease in (3)H-cAMP binding sites (t-test; P<0.01), with a significant difference between BD and controls (t-test; P<0.01). This presence of Sp-cAMP also results in increased BDNF expression (t-test, P<0.01), but neither in resting cells, nor in stimulated cells, was any difference observed in BDNF expression between BD and controls (t-test, NS). LIMITATIONS This study was conducted on a peripheral model cell, whose importance of BDNF is unknown. CONCLUSIONS These data suggest that the upregulation of cAMP signaling observed in BD patients results in the normalization of the BDNF expression. Studies on signal transduction, gene expression and pathologies have implications for development of novel treatments.

Drug-Induced Decrease of Protein Kinase A Activity Reveals Alteration in BDNF Expression of Bipolar Affective Disorder

Bipolar affective disorder (BAD) is a severe disease whose molecular and cellular bases are not well known. The aim of the present study was to probe the cAMP signaling downstream targets by pharmacologically manipulating the protein kinase A (PKA) enzyme, along with the assessment of brain-derived neurotrophic factor (BDNF) expression in lymphoblasts. The time course of lymphoblast PKA activity (up to 72 h) revealed optimal activity at 24 h. Then, the enzyme activity and protein levels of PKA Cα subunit and phopsho-cAMP responsive element binding (CREB) were assayed in lymphoblasts derived from 12 BAD and 12 control (CT) subjects and cultured for 24 h in the presence of cAMP analog drugs. The results indicated that basal PKA activity and PKA Cα subunit immunolabeling are increased in cells from BAD compared with controls. Enzyme activity was increased by Sp-isomer in BAD and in CTs cells, without change in protein levels. In contrast, the Rp-isomer decreased enzyme activity and protein levels. In drug-naive conditions, there was no change in BDNF expression of BAD cells compared with CT cells. Treatment with Sp-isomer induced increased BDNF in both groups, while treatment with Rp-isomer induced a significant decrease in BDNF expression of BAD compared with CT. The p-CREB changes followed changes in BDNF levels, with increased and decreased Sp-isomer and Rp-isomer treatment, respectively. Our results suggest that mood disorder is associated with PKA upregulation and this could mask alteration in BDNF expression, because slowing down of PKA signaling results in a decrease of BDNF expression. These findings, combined with previous reports, provide a new insight to explain pharmacological features in different diagnostic groups.

Differential changes of cAMP-dependent protein kinase activity and 3H-cAMP binding sites in rat hippocampus during maturation and aging.

The cyclic AMP-dependent protein kinase (PKA) has been involved in the brain aging process and recent papers have reported age-associated changes in enzyme activity in rat brain. The present study was undertaken to assess simultaneously PKA activity and regulatory (R) subunit levels during maturation and aging. Five cohorts of rats of different ages were used, namely pups of 1 week and 3 weeks old, mature rats (2 months), postmature rats (1 year) and old rats (2 years or more). PKA activity and 3H-cAMP binding sites were determined in cytosolic fractions of hippocampus. Results showed a low PKA activity in newborn rats which increased in mature and postmature rats and finally declined in old rats (ANOVA, P<0.001). The maximum binding sites (Bmax) of 3H-cAMP which measure the PKA R subunit levels were elevated in newborn rats and declined in mature and old rats (ANOVA; P<0.001). It is suggested the changes in PKA R subunit levels reflect an adaptative role in maturing process, a role which is lost in aging phase.

Lithium and Haloperidol Treatments Differently Affect the Mononuclear Leukocyte Gαs Protein Levels in Bipolar Affective Disorder

Despite numerous suggestions of the involvement of GTP-binding proteins in the mechanisms of action of psychoactive drugs in bipolar affective disorder, few studies have been conducted during the drug treatment of patients. The aim of the present study was to investigate the effects of a mood stabilizer and an antipsychotic drug on Gαs proteins. Patients with bipolar affective disorder under lithium treatment with or without haloperidol were assessed with respect to their mononuclear leukocyte (MNL) Gαs subunit protein. Gαs-45 protein subunit levels were analyzed by the Western immunoblot method. The subjects consisted of a group of 20 patients, all diagnosed as euthymic bipolars, and a comparison group of 15 drug-free healthy subjects. Results showed that Gαs levels were significantly decreased in the bipolar patients (BP) compared to drug-free healthy subjects (Mann-Whitney U test, p < 0.002). The drug effect was evaluated by a factorial analysis of variance and showed significant differences between groups (Kruskal-Wallis H test, p < 0.02). Lithium-treated patients displayed the most decreased Gαs levels (normalized mean values 53.2 ± 31 vs. 122 ± 45% for BP and controls, respectively, p < 0.001), while no change was observed in Gαs levels of haloperidol-treated patients compared to controls (mean values: 124.9 ± 37%; NS). The data indicate that lithium and haloperidol affect the mechanism of Gαs protein signal transduction differently, consistent with previous animal studies.