Kazue Hisaoka

Antidepressant drug treatments induce glial cell line‐derived neurotrophic factor (GDNF) synthesis and release in rat C6 glioblastoma cells

Modulation of neurotrophic factors to protect neurons from damage is proposed as a novel mechanism for the action of antidepressants. However, the effect of antidepressants on modulation of glial cell line‐derived neurotrophic factor (GDNF), which has potent and widespread effects, remains unknown. Here, we demonstrated that long‐term use of antidepressant treatment significantly increased GDNF mRNA expression and GDNF release in time‐ and concentration‐dependent manners in rat C6 glioblastoma cells. Amitriptyline treatment also increased GDNF mRNA expression in rat astrocytes. GDNF release continued for 24 h following withdrawal of amitriptyline. Furthermore, following treatment with antidepressants belonging to several different classes (amitriptyline, clomipramine, mianserin, fluoxetine and paroxetine) significantly increased GDNF release, but which did not occur after treatment with non‐antidepressant psychotropic drugs (haloperidol, diazepam and diphenhydramine). Amitriptyline‐induced GDNF release was inhibited by U0126 (10 µm), a mitogen‐activated protein kinase (MAPK)‐extracellular signal‐related kinase (ERK) kinase (MEK) inhibitor, but was not inhibited by H‐89 (1 µm), a protein kinase A inhibitor, calphostin C (100 nm), a protein kinase C inhibitor and PD 169316 (10 µm), a p38 mitogen‐activated protein kinase inhibitor. These results suggested that amitriptyline‐induced GDNF synthesis and release occurred at the transcriptional level, and may be regulated by MEK/MAPK signalling. The enhanced and prolonged induction of GDNF by antidepressants could promote neuronal survival, and protect neurons from the damaging effects of stress. This may contribute to explain therapeutic action of antidepressants and suggest new strategies of pharmacological intervention.

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.

Serotonin increases glial cell line-derived neurotrophic factor release in rat C6 glioblastoma cells.

Antidepressants, which increase monoamine levels, induce glial cell line-derived neurotrophic factor (GDNF) release in C6 cells. Thus, we examined whether monoamines affect on GDNF release in C6 cells. We found that serotonin (5-HT) specifically increased GDNF mRNA expression and GDNF release in a dose- and time-dependent manner. The 5-HT-induced GDNF release was mediated through the MEK/mitogen-activated protein kinase (MAPK) pathway and, at least, 5-HT(2A) receptors. The action of 5-HT on GDNF release may provide important insights into the mechanism of antidepressants.

Activation of transient receptor potential ankyrin 1 evokes nociception through substance P release from primary sensory neurons

J. Neurochem. (2012) 120, 1036–1047.

Noradrenergic regulation of period1 expression in spinal astrocytes is involved in protein kinase A, c-Jun N-terminal kinase and extracellular signal-regulated kinase activation mediated by α1- and β2-adrenoceptors.

Our recent data suggest that noradrenaline (NA) regulates expression of Per1 mRNA in rat C6 cells, as a model of brain astrocytes, by two distinct NA-mediating pathways. Although C6 cells possess potential astrocyte-type characteristics, we hypothesize that astrocytes located in a distinct tissue or organ play specific roles consistent with their own unique functions in response to the surrounding environment. We have herein found in primary rat spinal astrocytes using real-time RT-PCR that NA induced robust transient increases in Per1, Cry1, Cry2 and Bmal1 mRNA expression. Cry1, Cry2 and Bmal1 expressions induced by NA were attenuated by transfection of Per1 small interference RNA (siRNA). The effect of NA on Per1 expression was partially blocked by either prazosin (a selective antagonist of α1-adrenoceptor) or ICI118551 (a selective antagonist of β2-adrenoceptor), and completely blocked by the combination of both antagonists. Treatment with H89 (a protein kinase A [PKA] inhibitor), SP600125 (a c-Jun N-terminal kinase [JNK] inhibitor), or PD98059 (an extracellular signal-regulated kinase [ERK] inhibitor), partially inhibited NA-induced Per1 mRNA expression, and the combination of these three inhibitors inhibited expression to nearly a non-stimulated level. Furthermore, NA phosphorylated not only ERK but also JNK1, an effect that was detected by western blotting. These actions were inhibited only by prazosin, and not by ICI118551. In addition, we found that NA induced phosphorylation of transcription-related proteins such as cAMP response element binding protein (CREB) and c-Jun. These phosphorylation processes were regulated through distinct pathways: CREB phosphorylation was dependent on the PKA and JNK pathways but c-Jun phosphorylation was mediated by the ERK and JNK pathways. These results suggest that Per1 plays a key role in noradrenergic regulation on clock gene expression in spinal astrocytes and activation of α1 and β2 adrenoceptors are of importance in regulation of Per1 mRNA expression via PKA/JNK-CREB and ERK/JNK-c-Jun cascades.

Antidepressant drugs and cytokines in mood disorders

This article reviews recent developments in cytokine research that pertain to pharmacological treatment of mood disorders such as antidepressants and lithium. We review the possible involvement of cytokines in mood disorders and their role in the therapeutic effects of antidepressant drugs. Growing evidence suggests that specific cytokines signal the brain to generate neurochemical, neuroimmune, neuroendocrine and behavior changes. An imbalance of cytokines within the central nervous system (CNS), or even systemically, may play a role in the pathophysiology of mood disorders. Modulation of these cytokines by chronic antidepressant treatment may result in restored balance. However, the effect of antidepressants on cytokines is still unclear both in clinical and preclinical research due to limited data. Further research is needed to clarify the involvement of cytokines in mood disorders. Understanding this relationship may lead to rational, therapeutic improvements in antidepressant and mood stabilizing drugs.