Chronic treatment with desipramine and fluoxetine modulate BDNF, CaMKKα and CaMKKβ mRNA levels in the hippocampus of transgenic mice expressing antisense RNA against the glucocorticoid receptor
Introduction
Major depressive disorders (MDDs) are common, severe, chronic and often life-threatening illnesses. Causes of MDDs are still unclear but it is well known that impairments in monoaminergic neurotransmitter availability and changes in monoaminergic receptor density characterize these diseases (Coppen, 1967, Leonard, 2000, Schildkaut, 1965). Recent studies have also associated MDDs with regional reductions in central nervous system (CNS) volume, as well as in the numbers and/or sizes of glia and neurons in discrete brain regions, including the hippocampus (Drevets, 2000, Manji et al., 2001, Rajkowska et al., 1999).
Antidepressant drugs are the most common therapeutic for the treatment of depression. A variety of studies have demonstrated that chronic antidepressant treatment indirectly regulates a number of factors involved in cell survival pathways, including CREB, BDNF, bcl-2 and MAP kinases (Manji et al., 2000). cAMP response element binding protein (CREB) can be phosphorylated and activated on Ser133 by many kinases: including protein kinase A (PKA), Ca2+-calmodulin-dependent protein kinases I and IV (CaMKI and IV), protein kinase C (PKC) and the Ras-MAPK signaling pathway (Montminy, 1997). When phosphorylated by CaMKKs, the affinity of CaMKIV for CREB is increased, with Vmax and KM values equivalent to those of PKA (Enslen et al., 1995). CaMKKα and CaMKKβ, which are encoded by two distinct genes, but share high homology, are widely expressed in the CNS and in peripheral tissues such as liver, spleen and testis (Anderson et al., 1998, Sakagami et al., 1998, Vinet et al., 2003). Recently, it has been demonstrated that the CaMK pathway regulates CREB-mediated transcription in vivo (Kimura et al., 2002) and CaMKKβ knockout mice have impaired CREB activation during spatial long-term memory formation (Peters et al., 2003).
Neuroendocrine changes, hypothalamic–pituitary–adrenal (HPA) axis hyperactivity and impaired glucocorticoid feedback have been demonstrated in 20–50% of depressed patients (Arborelius et al., 1999, Gold et al., 1995, Sapolsky, 2000). Stress is a major factor in the onset of depression and can results in the atrophy of CA3 neurons (Sheline et al., 1999, Whiteford et al., 1987). It has been shown that antidepressant drugs inhibit some changes evoked by glucocorticoids and stress (Jackson and Luo, 1998, Nibuya et al., 1995, Schaaf et al., 1998, Watanabe et al., 1992) and antidepressants can also affect glucocorticoid receptor (GR)-mediated gene transcription (Pepin et al., 1992a, Budziszewska et al., 2000), which can be modulated by CaMKs (Silver et al., 1986).
In order to study the effect of a disturbed HPA on brain function and on the mechanism of action of antidepressant drugs, a transgenic (TG) mouse with impaired type II GR function has been developed (Pepin et al., 1992b). These mice present a different pattern of GR mRNA and receptor density localization compared to normal mice. Moreover, they show different GR regulation and fail to respond adequately to a decision-making task when exposed to a chronic mild stress (Froger et al., 2004). These neurobiological and behavioral characteristics make the TG mice a good genetic model to use in depression-related studies. We have previously published the effects of antidepressant treatments on CREB mRNA expression in the hippocampus of TG mice (Blom et al., 2002). Here, we investigate the effects of chronic administration of desipramine (DMI) and fluoxetine (FLU) on the gene expression of different molecular targets, that are either upstream of CREB, such as CaMKKα and CaMKKβ, or downstream of CREB, such as brain-derived neurotrophic factor (BDNF).
Section snippets
Experimental animals
Adult male wild-type (Wt) B6C3F1 mice (Charles River Laboratories) and male homozygous transgenic mice (TG, line 5.4) were used in this study. Homozygous TG mice were generated by inserting in the genome of Wt B6C3F1 mice an inverted 1.815 kb fragment of the GR 3′ non-coding region coupled to a 2.3 kb EcoRI/HindIII human neurofilament gene promoter (Pepin et al., 1992b). These mice are characterized by a 50–70% diminution of GR mRNA in different brain areas. They fail to reduce ACTH levels when
Results
The effect of chronic antidepressant treatment on the expression of CaMKKα, CaMKKβ and BDNF mRNA in the hippocampus of Wt and TG mice was examined using in situ hybridization. Densitometric analysis was carried out in the CA1, CA3 and DG of the hippocampus. Distribution and relative expression of each mRNA analyzed was similar to those reported previously (Nibuya et al., 1995, Sakagami et al., 1998, Vinet et al., 2003). Data are summarized in Table 1. Only data of hippocampal subfields where
Discussion
MDDs have recently been associated with impairments in signaling pathways that regulate neuroplasticity and cell survival. A number of studies have identified critical components, in particular the transcription factor CREB and the neurotrophin BDNF, as potential long-term mediators of mood stabilization. CREB represents the convergence point of several transduction pathways: it can be phosphorylated by the protein kinases A and C (PKA, PKC), by the mitogen-activated protein kinases (MAPK) and
References (51)
- et al.
Components of a calmodulin-dependent protein kinase cascade. Molecular cloning, functional characterization and cellular localization of Ca2+/calmodulin-dependent protein kinase kinase beta
J. Biol. Chem
(1998) - et al.
Altered regulation of CREB by chronic antidepressant administration in the brain of transgenic mice with impaired glucocorticoid receptor function
Neuropsychopharmacology
(2002) - et al.
Acute application of the tricyclic antidepressant desipramine presynaptically stimulates the exocytosis of glutamate in the hippocampus
Neuroscience
(1999) - et al.
Depletion in serotonin decreases neurogenesis in the dentate gyrus and the subventricular zone of adult rats
Neuroscience
(1999) - et al.
Increased hippocampal BDNF immunoreactivity in subjects treated with antidepressant medication
Biol. Psychiatry
(2001) - et al.
Bi-phasic change in BDNF gene expression following antidepressant drug treatment
Neuropharmacology
(2003) Functional anatomical abnormalities in limbic and prefrontal cortical structures in major depression
Prog. Brain Res
(2000)- et al.
Phosphorylation of CREB by CaM-kinase IV activated by CaM-kinase IV kinase
Biochem. Biophys. Res. Commun
(1995) - et al.
Antidepressants and protein kinases: desipramine treatment affects pineal gland cAMP-dependent protein kinase activity
Eur. J. Pharmacol
(1986) - et al.
Evidence for a functional interaction between calmodulin and the glucocorticoid receptor
Biochem. Biophys. Res. Commun
(1995)
Morphometric evidence for neuronal and glial prefrontal cell pathology in major depression
Biol. Psychiatry
Phosphorylation and inhibition of rat glucocorticoid receptor transcriptional activation by glycogen synthase kinase-3 (GSK-3). Species-specific differences between human and rat glucocorticoid receptor signaling as revealed through GSK-3 phosphorylation
J. Biol. Chem
Localization of the mRNAs for two isoforms of Ca2+/calmodulin-dependent protein kinase kinases in the adult rat brain
Brain Res. Mol. Brain Res
Downregulation of BDNF mRNA and protein in the rat hippocampus by corticosterone
Brain Res
Antidepressants and protein kinases: inhibition of Ca2+-regulated myosin phosphorylation by fluoxetine and iprindole
Eur. J. Pharmacol
Dexamethasone nonsuppression in transgenic mice expressing antisense RNA to the glucocorticoid receptor
J. Psychiatry Res
Cloning of mouse Ca(2+)/calmodulin-dependent protein kinase kinase beta (CaMKKbeta) and characterization of CaMKKbeta and CaMKKalpha distribution in the adult mouse brain
Brain Res. Mol. Brain Res
Tianeptine attenuates stress-induced morphological changes in the hippocampus
Eur. J. Pharmacol
Elevated baseline and postdexamethasone cortisol levels. A reflection of severity or endogeneity?
J. Affect. Disord
The role of corticotropin-releasing factor in depression and anxiety disorders
J. Endocrinol
Antidepressant drugs inhibit glucocorticoid receptor-mediated gene transcription—a possible mechanism
Br. J. Pharmacol
Regulation of adult neurogenesis by excitatory input and NMDA receptor activation in the dentate gyrus
J. Neurosci
The biochemistry of affective disorders
Br. J. Psychiatry
Central 5-hydroxytryptamine-2A receptor expression in transgenic mice bearing a glucocorticoid receptor antisense
Neuroendocrinology
Neurochemical and behavioral alterations in glucocorticoid receptor-impaired transgenic mice after chronic mild stress
J. Neurosci
Cited by (0)
- 1
These authors equally participated to this work.