Global epigenetic analysis of BDNF Val66Met mice hippocampus reveals changes in dendrite and spine remodeling genes.

Brain-derived neurotrophic factor (BDNF), a neurotrophin highly expressed in the hippocampus, plays crucial roles in cognition, neuroplasticity, synaptic function, and dendritic remodeling. The common human Val66Met polymorphism of BDNF has been implicated in the pathophysiology of neuropsychiatric and neurodegenerative disorders, and in the outcome of pro-adaptive and therapeutic treatments. Altered gene-expression profile has been previously shown in BDNF Val66Met knock-in mice, which recapitulate the phenotypic hallmarks of individuals carrying the BDNF Met allele. The aim of this study was to investigate the impact of the BDNF Val66Met polymorphism in the knock-in mouse model on two hippocampal epigenetic marks for transcriptional repression and activation, respectively: trimethylation of lysine 27 on histone H3 (H3K27me3) and acetylation of histone H3 (AcH3), using a genome-wide approach. Chromatin immunoprecipitation followed by deep sequencing of immunoprecipitated DNA (ChIP-Seq) was carried out with specific antibodies for H3K27me3 and AcH3. Our results revealed broad alteration of H3K27me3 and AcH3 marks association profiles in BDNFMet/Met , compared to BDNFVal/Val mice. Bioinformatics analysis showed changes in several biological functions and related pathways, affected by the presence of the polymorphism. In particular, a number of networks of functional interaction contained BDNF as central node. Quantitative PCR analysis confirmed epigenetically related significant changes in the expression of five genes: Dvl1, Nos3, Reln, Lypd6, and Sh3gl2. The first three are involved in dendrite and spine remodeling, morphological features altered in BDNFMet/Met mice. This work in homozygous knock-in mice shows that the human BDNF Val66Met polymorphism induces an array of histone H3 epigenetic modifications, in turn altering the expression of select genes crucial for structural and functional neuronal features.

Time-dependent activation of MAPK/Erk1/2 and Akt/GSK3 cascades: modulation by agomelatine.

BACKGROUND: The novel antidepressant agomelatine, a melatonergic MT1/MT2 agonist combined with 5-HT2c serotonin antagonist properties, showed antidepressant action in preclinical and clinical studies. There is a general agreement that the therapeutic action of antidepressants needs the activation of slow-onset adaptations in downstream signalling pathways finally regulating neuroplasticity. In the last several years, particular attention was given to cAMP-responsive element binding protein (CREB)-related pathways, since it was shown that chronic antidepressants increase CREB phosphorylation and transcriptional activity, through the activation of calcium/calmodulin-dependent (CaM) and mitogen activated protein kinase cascades (MAPK/Erk1/2). Aim of this work was to analyse possible effects of chronic agomelatine on time-dependent changes of different intracellular signalling pathways in hippocampus and prefrontal/frontal cortex of male rats. To this end, measurements were performed 1 h or 16 h after the last agomelatine or vehicle injection. RESULTS: We have found that in naïve rats chronic agomelatine, contrary to traditional antidepressants, did not increase CREB phosphorylation, but modulates the time-dependent regulation of MAPK/Erk1/2 and Akt/glycogen synthase kinase-3 (GSK-3) pathways. CONCLUSION: Our results suggest that the intracellular molecular mechanisms modulated by chronic agomelatine may be partly different from those of traditional antidepressants and involve the time-dependent regulation of MAPK/Erk1/2 and Akt/GSK-3 signalling pathways. This could exert a role in the antidepressant efficacy of the drug.

Chronic treatment with agomelatine or venlafaxine reduces depolarization-evoked glutamate release from hippocampal synaptosomes.

BACKGROUND: Growing compelling evidence from clinical and preclinical studies has demonstrated the primary role of alterations of glutamatergic transmission in cortical and limbic areas in the pathophysiology of mood disorders. Chronic antidepressants have been shown to dampen endogenous glutamate release from rat hippocampal synaptic terminals and to prevent the marked increase of glutamate overflow induced by acute behavioral stress in frontal/prefrontal cortex. Agomelatine, a new antidepressant endowed with MT1/MT2 agonist and 5-HT2C serotonergic antagonist properties, has shown efficacy at both preclinical and clinical levels. RESULTS: Chronic treatment with agomelatine, or with the reference drug venlafaxine, induced a marked decrease of depolarization-evoked endogenous glutamate release from purified hippocampal synaptic terminals in superfusion. No changes were observed in GABA release. This effect was accompanied by reduced accumulation of SNARE protein complexes, the key molecular effector of vesicle docking, priming and fusion at presynaptic membranes. CONCLUSIONS: Our data suggest that the novel antidepressant agomelatine share with other classes of antidepressants the ability to modulate glutamatergic transmission in hippocampus. Its action seems to be mediated by molecular mechanisms located on the presynaptic membrane and related with the size of the vesicle pool ready for release.

Abnormal exocytotic release of glutamate in a mouse model of amyotrophic lateral sclerosis.

Glutamate-mediated excitotoxicity plays a major role in the degeneration of motor neurons in amyotrophic lateral sclerosis and reduced astrocytary glutamate transport, which in turn increases the synaptic availability of the amino acid neurotransmitter, was suggested as a cause. Alternatively, here we report our studies on the exocytotic release of glutamate as a possible source of excessive glutamate transmission. The basal glutamate efflux from spinal cord nerve terminals of mice-expressing human soluble superoxide dismutase (SOD1) with the G93A mutation [SOD1/G93A(+)], a transgenic model of amyotrophic lateral sclerosis, was elevated when compared with transgenic mice expressing the wild-type human SOD1 or to non-transgenic controls. Exposure to 15 mM KCl or 0.3 µM ionomycin provoked Ca(2+)-dependent glutamate release that was dramatically increased in late symptomatic and in pre-symptomatic SOD1/G93A(+) mice. Increased Ca(2+) levels were detected in SOD1/G93A(+) mouse spinal cord nerve terminals, accompanied by increased activation of Ca(2+)/calmodulin-dependent kinase II and increased phosphorylation of synapsin I. In line with these findings, release experiments suggested that the glutamate release augmentation involves the readily releasable pool of vesicles and a greater capability of these vesicles to fuse upon stimulation in SOD1/G93A(+) mice.

Antidepressant treatments change 5-HT2C receptor mRNA expression in rat prefrontal/frontal cortex and hippocampus.

BACKGROUND/AIMS: Compelling evidence would suggest the involvement of the serotonin 2C receptor in the pathophysiology of affective disorders and in the action of antidepressants. We analyzed the time course of 5-HT2C receptor (5-HTR2C) mRNA expression during antidepressant treatment in the prefrontal/frontal cortex (P/FC) and in the hippocampus (HC) of rats chronically treated with fluoxetine (a selective serotonin reuptake inhibitor) and reboxetine (a selective noradrenaline reuptake inhibitor). We also analyzed the 5-HTR2C RNA-editing levels at the sites called A, B, C, C' and D, which are known to modulate 5-HTR2C receptor function. RESULTS: The expression profile of 5-HTR2C mRNA was modified during treatment with both antidepressants. In particular, we found a general down-regulation of 5-HTR2C mRNA expression in P/FC, which became significant after 3 weeks of treatment with both antidepressants and persisted after a fourth week of drug withdrawal (-46% with fluoxetine, -41% with reboxetine, p < 0.05). In HC, however, reboxetine induced significant down-regulation (-56%, p < 0.05) of 5-HTR2C mRNA after 3 weeks, while fluoxetine induced threefold up-regulation (p < 0.01) by the 2nd and 3rd week, returning to the base level after drug withdrawal of both antidepressants. Moreover, the frequency of 5-HTR2C-edited isoforms showed no significant alterations, although analysis of the RNA-editing level at the single editing sites showed small decreases in the C' and D sites induced by reboxetine in P/FC. CONCLUSION: Our results suggest that chronic administration of antidepressants in rats slightly modifies the editing levels of 5-HT2C receptor but has considerable influence on its mRNA expression patterns in a way that is area- and time-specific.

miR-9-5p is involved in the rescue of stress-dependent dendritic shortening of hippocampal pyramidal neurons induced by acute antidepressant treatment with ketamine.

Converging clinical and preclinical evidence demonstrates that depressive phenotypes are associated with synaptic dysfunction and dendritic simplification in cortico-limbic glutamatergic areas. On the other hand, the rapid antidepressant effect of acute ketamine is consistently reported to occur together with the rescue of dendritic atrophy and reduction of spine number induced by chronic stress in the hippocampus and prefrontal cortex of animal models of depression. Nevertheless, the molecular mechanisms underlying these morphological alterations remain largely unknown. Here, we found that miR-9-5p levels were selectively reduced in the hippocampus of rats vulnerable to Chronic Mild Stress (CMS), while acute subanesthetic ketamine restored its levels to basal condition in just 24h; miR-9-5p expression inversely correlated with the anhedonic phenotype. A decrease of miR-9-5p was reproduced in an in vitro model of stress, based on primary hippocampal neurons incubated with the stress hormone corticosterone. In both CMS animals and primary neurons, decreased miR-9-5p levels were associated with dendritic simplification, while treatment with ketamine completely rescued the changes. In vitro modulation of miR-9-5p expression showed a direct role of miR-9-5p in regulating dendritic length and spine density in mature primary hippocampal neurons. Among the putative target genes tested, Rest and Sirt1 were validated as biological targets in primary neuronal cultures. Moreover, in line with miR-9-5p changes, REST protein expression levels were remarkably increased in both CMS vulnerable animals and corticosterone-treated neurons, while ketamine completely abolished this alteration. Finally, the shortening of dendritic length in corticosterone-treated neurons was shown to be partly rescued by miR-9-5p overexpression and dependent on REST protein expression. Overall, our data unveiled the functional role of miR-9-5p in the remodeling of dendritic arbor induced by stress/corticosterone in vulnerable animals and its rescue by acute antidepressant treatment with ketamine.

Blockade of stress-induced increase of glutamate release in the rat prefrontal/frontal cortex by agomelatine involves synergy between melatonergic and 5-HT2C receptor-dependent pathways.

BACKGROUND: Agomelatine is a melatonergic receptor agonist and a 5HT2C receptor antagonist that has shown antidepressant efficacy. In order to analyze separately the effect of the two receptorial components, rats were chronically treated with agomelatine, melatonin (endogenous melatonergic agonist), or S32006 (5-HT2C antagonist), and then subjected to acute footshock-stress. RESULTS: Only chronic agomelatine, but not melatonin or S32006, completely prevented the stress-induced increase of glutamate release in the rat prefrontal/frontal cortex. CONCLUSIONS: These results suggest a potential synergy between melatonergic and serotonergic pathways in the action of agomelatine.

Blues in the Brain and Beyond: Molecular Bases of Major Depressive Disorder and Relative Pharmacological and Non-Pharmacological Treatments.

Despite the extensive research conducted in recent decades, the molecular mechanisms underlying major depressive disorder (MDD) and relative evidence-based treatments remain unclear. Various hypotheses have been successively proposed, involving different biological systems. This narrative review aims to critically illustrate the main pathogenic hypotheses of MDD, ranging from the historical ones based on the monoaminergic and neurotrophic theories, through the subsequent neurodevelopmental, glutamatergic, GABAergic, inflammatory/immune and endocrine explanations, until the most recent evidence postulating a role for fatty acids and the gut microbiota. Moreover, the molecular effects of established both pharmacological and non-pharmacological approaches for MDD are also reviewed. Overall, the existing literature indicates that the molecular mechanisms described in the context of these different hypotheses, rather than representing alternative ones to each other, are likely to contribute together, often with reciprocal interactions, to the development of MDD and to the effectiveness of treatments, and points at the need for further research efforts in this field.

Early raise of BDNF in hippocampus suggests induction of posttranscriptional mechanisms by antidepressants.

BACKGROUND: The neurotrophin BDNF has been implicated in the regulation of neuroplasticity, gene expression, and synaptic function in the adult brain, as well as in the pathophysiology of neuropsychiatric disorders and the mechanism of action of antidepressants. Antidepressant treatments have been shown to increase the expression of BDNF mRNA, although the changes measured were found to be different depending on various factors. A few studies only have measured levels of BDNF protein after antidepressant treatments, and poor correlation was found between mRNA and protein changes. We studied the time course of expression of BDNF mRNA and protein during drug treatments, in order to elucidate the temporal profile of regulation of this effector and whether mRNA and protein levels correlate. Rat groups were treated for 1, 2 or 3 weeks with fluoxetine or reboxetine; in additional groups drug treatment was followed by a washout week (3+1). Total BDNF mRNA was measured by Real Time PCR, pro- and mature BDNF proteins were measured by Western blot. RESULTS: We found that mature BDNF protein is induced more rapidly than mRNA, by both drugs in hippocampus (weeks 1-2) and by reboxetine in prefrontal/frontal cortex (week 1). The temporal profile of BDNF protein expression was largely inconsistent with that of mRNA, which followed the protein induction and reached a peak at week 3. CONCLUSION: These results suggest that BDNF protein is rapidly elevated by antidepressant treatments by posttranscriptional mechanisms, and that induction of BDNF mRNA is a slower process.

Early induction of CREB activation and CREB-regulating signalling by antidepressants.

Converging evidence points to adaptive changes in neuroplasticity and gene expression as mediators of therapeutic action of antidepressants. Activation of cAMP response-element binding protein (CREB) and CREB-regulating signalling are considered main effectors in these mechanisms. We analysed the temporal profile of intracellular changes induced by antidepressants, by measuring activation of major CREB-regulating signalling cascades and activation (Ser133 phosphorylation) of CREB. The main aims of the study were to investigate how these different variables are modulated with time, whether stronger activation of signalling cascades corresponds to stronger activation of CREB, and whether these changes are different in distinct brain areas. Rat groups were treated for 1, 2 or 3 wk with the antidepressants fluoxetine or reboxetine; in additional groups drug treatment was followed by a washout week (3+1). Activation of CREB and major effectors in signalling cascades were analysed by Western blot analysis with phospho-antibodies, in nuclear and cytosolic fractions from hippocampus and prefrontal/frontal cortex (P/FC). Surprisingly, CREB activation was already maximal after 1-wk treatment. In hippocampus early and stronger CREB activation was consistent with early and stronger activation of signalling. For both drugs, the profile of activation in P/FC was different from that observed in hippocampus. The results also showed that, contrary to the activatory role of MAP-ERKs and CaM kinase IV, nuclear alphaCaM kinase II was inactivated in parallel with activation of CREB.

Remodelling by early-life stress of NMDA receptor-dependent synaptic plasticity in a gene-environment rat model of depression.

An animal model of depression combining genetic vulnerability and early-life stress (ELS) was prepared by submitting the Flinders Sensitive Line (FSL) rats to a standard paradigm of maternal separation. We analysed hippocampal synaptic transmission and plasticity in vivo and ionotropic receptors for glutamate in FSL rats, in their controls Flinders Resistant Line (FRL) rats, and in both lines subjected to ELS. A strong inhibition of long-term potentiation (LTP) and lower synaptic expression of NR1 subunit of the NMDA receptor were found in FSL rats. Remarkably, ELS induced a remodelling of synaptic plasticity only in FSL rats, reducing inhibition of LTP; this was accompanied by marked increase of synaptic NR1 subunit and GluR2/3 subunits of AMPA receptors. Chronic treatment with escitalopram inhibited LTP in FRL rats, but this effect was attenuated by prior ELS. The present results suggest that early gene-environment interactions cause lifelong synaptic changes affecting functional and molecular aspects of plasticity, partly reversed by antidepressant treatments.

Time-dependent biphasic modulation of human BDNF by antidepressants in neuroblastoma cells.

BACKGROUND: Recent rodent studies reported that antidepressant treatments affect the expression of brain-derived neurotrophic factor (BDNF) mRNA in a way that is dependent on treatment duration, by selective modulation of different BDNF transcripts. However, no data are available for the human BDNF gene. We studied the effect of different antidepressants on BDNF mRNA expression in human neuroblastoma SH-SY5Y cells. RESULTS: Cultured cells were treated with the antidepressants fluoxetine, reboxetine and desipramine for different time lengths (6, 24, 48 hours). Expression of total BDNF mRNA was analyzed by reverse transcription PCR and levels of different BDNF transcripts were detected by hemi-nested PCR with specific primers. Short-term treatment (6 hours) with reboxetine or desipramine reduced total BDNF, whereas long-term treatment (48 hours) significantly increased total BDNF mRNA levels. These changes were accounted for by differential regulation of BDNF IV and VIa/b transcripts. Fluoxetine showed no significant effects. CONCLUSION: This is the first study showing biphasic changes in the expression of total and specific BDNF transcripts in human cells following antidepressant treatments. These findings suggest that biphasic induction of BDNF by antidepressants could be a feature common to rodents and humans and encourage the use of SH-SY5Y cells as a tool for investigation of drug effects on human genes.

Chronic antidepressants induce redistribution and differential activation of alphaCaM kinase II between presynaptic compartments.

Changes in synaptic plasticity are involved in pathophysiology of depression and in the mechanism of antidepressants. Ca(2+)/calmodulin (CaM) kinase II, a protein kinase involved in synaptic plasticity, has been previously shown to be a target of antidepressants. We previously found that antidepressants activate the kinase in hippocampal neuronal cell bodies by increasing phosphorylation at Thr(286), reduce the kinase phosphorylation in synaptic membranes, and in turn its phosphorylation-dependent interaction with syntaxin-1 and the release of glutamate from hippocampal synaptosomes. Here, we investigated the chronic effect of different antidepressants (fluoxetine, desipramine, and reboxetine) on the expression and function of the kinase in distinct subcellular compartments in order to dissect the different kinase pools affected. Acute treatments did not induce any change in the kinase. In total tissue extracts chronic drug treatments induced activation of the kinase; in hippocampus (HC), but not in prefrontal/frontal cortex, this was partially accounted for by increased Thr(286) phosphorylation, suggesting the involvement of different mechanisms of activation. In synaptosomes, all drugs reduced the kinase phosphorylation, particularly in HC where, upon fractionation of the synaptosomal particulate into synaptic vesicles and membranes, we found that the drugs induced a redistribution and differential activation of the kinase between membranes and vesicles. Furthermore, a large decrease in the level and phosphorylation of synapsin I located at synaptic membranes was consistent with the observed decrease of CaM kinase II. Overall, antidepressants induce a complex pattern of modifications in distinct subcellular compartments; at presynaptic level, these changes are in line with a dampening of glutamate release.

Regulation of editing and expression of glutamate alpha-amino-propionic-acid (AMPA)/kainate receptors by antidepressant drugs.

BACKGROUND: Several reports have shown that the glutamatergic system is involved in both the pathogenesis of affective and stress-related disorders and in the action of antidepressant drugs. In particular, antidepressant treatment was shown to modulate expression and function of ionotropic glutamate receptors, to inhibit glutamate release and to restore synaptic plasticity impaired by stress. METHODS: We analyzed the mRNA expression and RNA editing of alpha-amino-propionic-acid (AMPA) and kainate (KA) receptor subunits, in the pre-frontal/frontal cortex (P/FC) and hippocampus (HI) of rats chronically treated with three different drugs: the selective serotonin (5-HT) reuptake inhibitor fluoxetine, the selective noradrenaline (NA) reuptake inhibitor reboxetine and the tricyclic antidepressant desipramine. RESULTS: Our data showed that fluoxetine and desipramine exerted moderate but selective effects on glutamate receptor expression and editing, while reboxetine appeared to be the drug that affects glutamate receptors (GluR) most. The most consistent effect, observed with pronoradrenergic drugs (desipramine and reboxetine), was a decrease of GluR3 expression both in P/FC and HI. Interestingly, in HI, the same drugs also decreased the editing levels of either the flip (desipramine) or flop (reboxetine) form of GluR3. CONCLUSIONS: Overall, these results point to specific and regionally discrete changes in the expression and editing level of glutamate receptors and, in particular, to a selective reduction of conductance for GluR3-containing receptors following treatment with antidepressant drugs. These data support the hypothesis that changes in glutamate neurotransmission are involved in the therapeutic effects induced by these drugs.

Peripheral whole blood microRNA alterations in major depression and bipolar disorder.

Major depression (MD) and bipolar disorder (BD) are severe and potentially life-threating mood disorders whose etiology is to date not completely understood. MicroRNAs (miRNAs) are small non-coding RNAs that regulate protein synthesis post-transcriptionally by base-pairing to target gene mRNAs. Growing evidence indicated that miRNAs might play a key role in the pathogenesis of neuropsychiatric disorders and in the action of psychotropic drugs. On these bases, in this study we evaluated the expression levels of 1733 mature miRNAs annotated in miRBase v.17, through a microarray technique, in the blood of 20 MD and 20 BD patients and 20 healthy controls, in order to identify putative miRNA signatures associated with mood disorders. We found that 5 miRNAs (hsa-let-7a-5p, hsa-let-7d-5p, hsa-let-7f-5p, hsa-miR-24-3p and hsa-miR-425-3p) were specifically altered in MD patients and 5 (hsa-miR-140-3p, hsa-miR-30d-5p, hsa-miR-330-5p, hsa-miR-378a-5p and hsa-miR-21-3p) in BD patients, whereas 2 miRNAs (hsa-miR-330-3p and hsa-miR-345-5p) were dysregulated in both the diseases. The bioinformatic prediction of the genes targeted by the altered miRNAs revealed the possible involvement of neural pathways relevant for psychiatric disorders. In conclusion, the observed results indicate a dysregulation of miRNA blood expression in mood disorders and could indicate new avenues for a better understanding of their pathogenetic mechanisms. The identified alterations may represent potential peripheral biomarkers to be complemented with other clinical and biological features for the improvement of diagnostic accuracy.

Expression and phosphorylation of delta-CaM kinase II in cultured Alzheimer fibroblasts.

Dysregulation of calcium homeostasis is among the major cellular alterations in Alzheimer's disease (AD). We studied Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II), one of the major effectors regulating neuronal responses to changes in calcium fluxes, in cultured skin fibroblasts from subjects with sporadic AD. We found, by using PCR and Western analysis, that human fibroblasts express the delta-isoform of this kinase, and that CaM kinase II is the major Ca(2+)/calmodulin-dependent kinase in these cells. Protein expression level of the kinase was not significantly different in AD fibroblasts. However, the total activity of the kinase (stimulated by Ca(2+)/calmodulin) was significantly reduced in AD cell lines, whereas Ca(2+)-independent activity was significantly enhanced. The percent autonomy of the kinase (%Ca(2+)-independent/Ca(2+)-dependent activity) in AD cell lines was 62.8%, three-fold the corresponding percentage in control fibroblasts. The abnormal calcium-independent activity was not due to enhanced basal autophosphorylation of Thr(287). The observed abnormalities, if present in brain tissue, may be implicated either in dysfunction of neuroplasticity and cognitive functions or in dysregulation of cell cycle.

Selective phosphorylation of nuclear CREB by fluoxetine is linked to activation of CaM kinase IV and MAP kinase cascades.

Regulation of gene expression is purported as a major component in the long-term action of antidepressants. The transcription factor cAMP-response element-binding protein (CREB) is activated by chronic antidepressant treatments, although a number of studies reported different effects on CREB, depending on drug types used and brain areas investigated. Furthermore, little is known as to what signaling cascades are responsible for CREB activation, although cAMP-protein kinase A (PKA) cascade was suggested to be a central player. We investigated how different drugs (fluoxetine (FLX), desipramine (DMI), reboxetine (RBX)) affect CREB expression and phosphorylation of Ser(133) in the hippocampus and prefrontal/frontal cortex (PFCX). Acute treatments did not induce changes in these mechanisms. Chronic FLX increased nuclear phospho-CREB (pCREB) far more markedly than pronoradrenergic drugs, particularly in PFCX. We investigated the function of the main signaling cascades that were shown to phosphorylate and regulate CREB. PKA did not seem to account for the selective increase of pCREB induced by FLX. All drug treatments markedly increased the enzymatic activity of nuclear Ca2+/calmodulin (CaM) kinase IV (CaMKIV), a major neuronal CREB kinase, in PFCX. Activation of this kinase was due to increased phosphorylation of the activatory residue Thr196, with no major changes in the expression levels of alpha- and beta-CaM kinase kinase, enzymes that phosphorylate CaMKIV. Again in PFCX, FLX selectively increased the expression level of MAP kinases Erk1/2, without affecting their phosphorylation. Our results show that FLX exerts a more marked effect on CREB phosphorylation and suggest that CaMKIV and MAP kinase cascades are involved in this effect.

The protein kinase A in platelets from patients with panic disorder.

Although previous studies suggested that dysfunctions in the protein kinase A (PKA) and in some of its substrates are associated with several psychiatric disorders, there is no evidence regarding the possible involvement of such components in panic disorder (PD). Thus, the aim of the present study was to investigate the levels of PKA and Rap1 in platelets from patients with such disorder. Twenty-four drug free patients with PD and 24 healthy volunteers participated to the study. Employing the Western Blot analysis, immunostaining and computer-assisted imaging, the levels of the regulatory (R, type I and type II) and the catalytic (C) subunits of PKA, and those of Rap1 were assessed in platelets from the two groups. The data show that patients with PD have significantly higher levels of platelet RI and C subunits of PKA than controls, whereas the levels of RII were unchanged. No significant differences were found in the immunolabelling of Rap1 between groups. These findings may provide clues toward understanding the involvement of cAMP signalling in anxiety disorders.

Protein kinase A activity in platelets from patients with bipolar disorder.

BACKGROUND: Abnormal levels of protein kinase A (PKA) were found in patients with bipolar disorder (BD). Since altered levels are generally accompanied by functional modifications, the purpose of this study was to investigate PKA activity in patients with BD. METHODS: PKA activity was assessed in platelets from 20 drug-free bipolar patients and 19 controls. RESULTS: The cAMP-stimulated PKA activity was significantly increased in bipolar patients compared with controls. LIMITATIONS: This study made use of platelets, which may not fully represent changes occurring in specific brain regions. CONCLUSION: This study adds to the growing evidence suggesting that abnormalities of PKA are associated with BD.

Micro spies from the brain to the periphery: new clues from studies on microRNAs in neuropsychiatric disorders.

microRNAs (miRNAs) are small non-coding RNAs (20-22 nucleotides) playing a major role in post-transcriptional regulation of gene expression. miRNAs are predicted to regulate more than 50% of all the protein-coding genes. Increasing evidence indicates that they may play key roles in the biological pathways that regulate neurogenesis and synaptic plasticity, as well as in neurotransmitter homeostasis in the adult brain. In this article we review recent studies suggesting that miRNAs may be involved in the pathophysiology of neuropsychiatric disorders and in the action of psychotropic drugs, in particular by analyzing the contribution of genomic studies in patients' peripheral tissues. Alterations in miRNA expression have been observed in schizophrenia, bipolar disorder, major depression, Parkinson's disease, Alzheimer's disease and other neuropsychiatric conditions. In particular, intriguing findings concern the identification of disease-associated miRNA signatures in peripheral tissues, or modifications in miRNA profiles induced by drug treatments. Furthermore, genetic variations in miRNA sequences and miRNA-related genes have been described in neuropsychiatric diseases. Overall, though still at a preliminary stage, several lines of evidence indicate an involvement of miRNAs in both the pathophysiology and pharmacotherapy of neuropsychiatric disorders. In this regard, the data obtained in peripheral tissues may provide further insights into the etiopathogenesis of several brain diseases and contribute to identify new biomarkers for diagnostic assessment improvement and treatment personalization.