Mami Tsuchioka

Decreased levels of whole blood glial cell line-derived neurotrophic factor (GDNF) in remitted patients with mood disorders

Recent post-mortem and imaging studies provide evidence for a glial reduction in different brain areas in mood disorders. This study was aimed to test whether glial cell line-derived neurotrophic factor (GDNF), a member of transforming growth factor (TGF)-beta superfamily, in blood levels was associated with mood disorders. We measured GDNF and TGF-beta levels in whole blood in remitted patients with mood disorders [n=56; major depressive disorders (MDD) 39, bipolar disorders (BD) 17] and control subjects (n=56). GDNF and TGF-beta were assayed with the sandwich ELISA method. Total GDNF levels were significantly lower in MDD and in BD than in control subjects (MDD, p=0.0003; BD, p=0.018), while no significant difference in total TGF-beta1 or total TGF-beta2 levels was found in these groups. Our study suggests that lower GDNF levels might be involved in the pathophysiology of mood disorders, although this preliminary study has several limitations.

Antidepressants Increase Glial Cell Line-Derived Neurotrophic Factor Production through Monoamine-Independent Activation of Protein Tyrosine Kinase and Extracellular Signal-Regulated Kinase in Glial Cells

Recent studies show that neuronal and glial plasticity are important for therapeutic action of antidepressants. We previously reported that antidepressants increase glial cell line-derived neurotrophic factor (GDNF) production in rat C6 glioma cells (C6 cells). Here, we found that amitriptyline, a tricyclic antidepressant, increased both GDNF mRNA expression and release, which were selectively and completely inhibited by mitogen-activated protein kinase kinase inhibitors. Indeed, treatment of amitriptyline rapidly increased extracellular signal-regulated kinase (ERK) activity, as well as p38 mitogen-activated protein kinase and c-Jun NH2-terminal kinase activities. Furthermore, different classes of antidepressants also rapidly increased ERK activity. The extent of acute ERK activation and GDNF release were significantly correlated to each other in individual antidepressants, suggesting an important role of acute ERK activation in GDNF production. Furthermore, antidepressants increased the acute ERK activation and GDNF mRNA expression in normal human astrocytes as well as C6 cells. Although 5-hydroxytryptamine (serotonin) (5-HT), but not noradrenaline or dopamine, increased ERK activation and GDNF release via 5-HT2A receptors, ketanserin, a 5-HT2A receptor antagonist, did not have any effect on the amitriptyline-induced ERK activation. Thus, GDNF production by amitriptyline was independent of monoamine. Both of the amitriptyline-induced ERK activation and GDNF mRNA expression were blocked by genistein, a general protein tyrosine kinase (PTK) inhibitor. Actually, we found that amitriptyline acutely increased phosphorylation levels of several phosphotyrosine-containing proteins. Taken together, these findings indicate that ERK activation through PTK regulates antidepressant-induced GDNF production and that the GDNF production in glial cells may be a novel action of the antidepressant, which is independent of monoamine.

Serotonin (5-HT) induces glial cell line-derived neurotrophic factor (GDNF) mRNA expression via the transactivation of fibroblast growth factor receptor 2 (FGFR2) in rat C6 glioma cells

We previously reported that serotonin (5‐HT) increased glial cell line‐derived neurotrophic factor (GDNF) release in a 5‐HT2 receptor (5‐HT2R) and mitogen‐activated protein kinase kinase/extracellular signal‐related kinase (MEK/ERK)‐dependent manner in rat C6 glioma cells (C6 cells), a model of astrocytes. We herein found that 5‐HT‐induced rapid ERK phosphorylation was blocked by 5‐HT2R antagonists in C6 cells. We therefore examined 5‐HT‐induced ERK phosphorylation to reveal the mechanism of 5‐HT‐induced GDNF mRNA expression. As 5‐HT‐induced ERK phosphorylation was blocked by inhibitors for Gαq/11 and fibroblast growth factor receptor (FGFR), but not for second messengers downstream of Gαq/11, 5‐HT2R‐mediated FGFR transactivation was suggested to be involved in the ERK phosphorylation. Although FGFR1 and 2 were functionally expressed in C6 cells, 5‐HT selectively phosphorylated FGFR2. Indeed, small interfering RNA for FGFR2, but not for FGFR1, blocked 5‐HT‐induced ERK phosphorylation. As Src family tyrosine kinase inhibitors and microtubule depolymerizing agents blocked 5‐HT‐induced FGFR2 phosphorylation, Src family tyrosine kinase and stabilized microtubules were suggested to act upstream of FGFR2. Finally, 5‐HT‐induced GDNF mRNA expression was also inhibited by the blockade of 5‐HT2R, FGFR, and Src family tyrosine kinase. In conclusion, our findings suggest that 5‐HT induces GDNF mRNA expression via 5‐HT2R‐mediated FGFR2 transactivation in C6 cells.

Tricyclic Antidepressant Amitriptyline Activates Fibroblast Growth Factor Receptor Signaling in Glial Cells INVOLVEMENT IN GLIAL CELL LINE-DERIVED NEUROTROPHIC FACTOR PRODUCTION

Recently, both clinical and animal studies demonstrated neuronal and glial plasticity to be important for the therapeutic action of antidepressants. Antidepressants increase glial cell line-derived neurotrophic factor (GDNF) production through monoamine-independent protein-tyrosine kinase, extracellular signal-regulated kinase (ERK), and cAMP responsive element-binding protein (CREB) activation in glial cells (Hisaoka, K., Takebayashi, M., Tsuchioka, M., Maeda, N., Nakata, Y., and Yamawaki, S. (2007) J. Pharmacol. Exp. Ther. 321, 148–157; Hisaoka, K., Maeda, N., Tsuchioka, M., and Takebayashi, M. (2008) Brain Res. 1196, 53–58). This study clarifies the type of tyrosine kinase and mechanism of antidepressant-induced GDNF production in C6 glioma cells and normal human astrocytes. The amitriptyline (a tricyclic antidepressant)-induced ERK activation was specifically and completely inhibited by fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitors and siRNA for FGFR1 and -2. Treatment with amitriptyline or several different classes of antidepressants, but not non-antidepressants, acutely increased the phosphorylation of FGFRs and FGFR substrate 2α (FRS2α). Amitriptyline-induced CREB phosphorylation and GDNF production were blocked by FGFR-tyrosine kinase inhibitors. Therefore, antidepressants activate the FGFR/FRS2α/ERK/CREB signaling cascade, thus resulting in GDNF production. Furthermore, we attempted to elucidate how antidepressants activate FGFR signaling. The effect of amitriptyline was inhibited by heparin, non-permeant FGF-2 neutralizing antibodies, and matrix metalloproteinase (MMP) inhibitors. Serotonin (5-HT) also increased GDNF production through FGFR2 (Tsuchioka, M., Takebayashi, M., Hisaoka, K., Maeda, N., and Nakata, Y. (2008) J. Neurochem. 106, 244–257); however, the effect of 5-HT was not inhibited by heparin and MMP inhibitors. These results suggest that amitriptyline-induced FGFR activation might occur through an extracellular pathway, in contrast to that of 5-HT. The current data show that amitriptyline-induced FGFR activation might occur by the MMP-dependent shedding of FGFR ligands, such as FGF-2, thus resulting in GDNF production.

Antidepressants induce acute CREB phosphorylation and CRE-mediated gene expression in glial cells: a possible contribution to GDNF production.

Recently, the changes of neuronal and glial plasticity related gene expression following the increase of monoamine are suggested to be important for the therapeutic effect of antidepressants. We previously showed that antidepressants increased glial cell line-derived neurotrophic factor (GDNF) expression, which was dependent on acute activation of protein tyrosine kinase (PTK) and extracellular signal-regulated kinase (ERK) in rat C6 glioma cells (C6 cells) and normal human astrocytes (NHA). Transcription of many genes including GDNF is directed by the cAMP responsive element (CRE) and its cognate transcription factor CRE binding protein (CREB). In this study, we showed that amitriptyline, a tricyclic antidepressant, acutely increased phosphorylation of CREB, without altering the level of total CREB in C6 cells as well as in NHA. In contrast, acute amitriptyline treatment did not affect phosphorylation of CREB in SH-SY5Y cells, a human neuroblastoma cell line. Different classes of antidepressants as well as amitriptyline acutely increased phosphorylation of CREB, but haloperidol and diazepam did not. The amitriptyline-induced phosphorylation of CREB was completely blocked by U0126 [a mitogen-activated protein (MAP) kinase kinase 1 inhibitor] and genistein (a PTK inhibitor), but not by inhibitors of protein kinase A, p38 MAP kinase, or Ca(2+)/calmodulin-dependent kinase. Amitriptyline treatment also increased the expression of luciferase reporter gene regulated by CRE elements. The amitriptyline-induced luciferase activity was completely inhibited by U0126 in the same as phosphorylation of CREB. These results suggest that antidepressants acutely increase CREB activity in PTK and ERK-dependent manners, which might contribute to gene expression including GDNF in glial cells.

Riluzole-induced glial cell line-derived neurotrophic factor production is regulated through fibroblast growth factor receptor signaling in rat C6 glioma cells.

Riluzole is approved for the treatment of amyotrophic lateral sclerosis (ALS); however, recent accumulating evidence suggests that riluzole is also effective for the treatment of psychiatric disorders, such as mood disorders. Plastic change in the brain induced by neurotrophic factors/growth factors is thought to be involved in the mechanism of antidepressants. This study investigated the mechanism of riluzole-induced glial cell line-derived neurotrophic factor (GDNF) production in rat C6 glioma cells (C6 cells), a model of astrocytes. The study investigated the phosphorylation of cAMP response element binding protein (CREB), an important transcriptional factor of the gdnf gene, and found that riluzole increased CREB phosphorylation in a time-dependent manner, peaking at 40min after treatment. The riluzole-induced CREB phosphorylation was completely blocked by a mitogen-activated protein kinase kinase (MEK) inhibitor (U0126). Riluzole increased extracellular signal-regulated kinase (ERK) activation prior to CREB phosphorylation. These results suggest that riluzole rapidly activates the MEK/ERK/CREB pathway. Furthermore, two types of fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitors (SU5402 and PD173074) completely blocked riluzole-induced CREB phosphorylation. In addition, riluzole rapidly phosphorylated FGFR substrate 2α (FRS2α), a major adaptor protein of FGFR. These findings suggest that riluzole induces CREB phosphorylation through FGFR. In addition, PD173074 inhibited riluzole-induced GDNF production. In contrast, l-glutamate and a glutamate transporter inhibitor (t-PDC) did not yield any effects in either CREB phosphorylation or GDNF production. These findings suggest that riluzole rapidly activates a MEK/ERK/CREB pathway through FGFR in a glutamate transporter-independent manner, followed by GDNF expression in C6 cells.

Asymmetric alternation of the hemodynamic response at the prefrontal cortex in patients with schizophrenia during electroconvulsive therapy: a near-infrared spectroscopy study.

OBJECTIVE Although electroconvulsive therapy (ECT) is a well-established treatment for psychiatric disorders, its mechanism of action remains unclear. To investigate the cerebral hemodynamic response during ECT, we measured the changes in the regional cerebral blood flow (rCBF) at the bilateral prefrontal cortex (PFC) using near-infrared spectroscopy (NIRS). Method. The participants included eleven patients with schizophrenia and ten patients with mood disorders. The normalized tissue hemoglobin index (nTHI) was used as a sensitive parameter of rCBF by the SRS method and was measured during bilateral ECT using a two-channel NIRS. Results. 1. All patients responded to ECT treatment. 2. The levels of bilateral nTHI indicated a transient decrease during electrical stimulation and immediately were increased at both ictal and post-ictal phases by approximately 20% above baseline. 3. Patients with schizophrenia, but not mood disorders, showed significant asymmetric alteration of nTHI levels (left>right) during both the ictal and post-ictal phases. 4. The asymmetry index of nTHI, which indicates the difference between the left and right sides of the nTHI, was negatively correlated with the period of illness for schizophrenia, although the asymmetry index was not significantly correlated with any other clinical data, such as the effect of ECT treatment. Conclusion. Preliminary data demonstrated that bilateral ECT caused hemodynamic changes in bilateral PFC, and asymmetric alteration was found for schizophrenia, but not for mood disorders. Although further studies are necessary, the asymmetric hemodynamic response by ECT may be associated with the pathophysiology of schizophrenia, especially in the early stages.