Early-life stress and antidepressant treatment involve synaptic signaling and Erk kinases in a gene-environment model of depression

Repeated cannabidiol treatment affects neuroplasticity and endocannabinoid signaling in the prefrontal cortex of the Flinders Sensitive Line (FSL) rat model of depression

Delayed therapeutic responses and limited efficacy are the main challenges of existing antidepressant drugs, thereby incentivizing the search for new potential treatments. Cannabidiol (CBD), non-psychotomimetic component of cannabis, has shown promising antidepressant effects in different rodent models, but its mechanism of action remains unclear. Herein, we investigated the antidepressant-like effects of repeated CBD treatment on behavior, neuroplasticity markers and lipidomic profile in the prefrontal cortex (PFC) of Flinders Sensitive Line (FSL), a genetic animal model of depression, and their control counterparts Flinders Resistant Line (FRL) rats. Male FSL animals were treated with CBD (10 mg/kg; i.p.) or vehicle (7 days) followed by Open Field Test (OFT) and the Forced Swimming Test (FST). The PFC was analyzed by a) western blotting to assess markers of synaptic plasticity and cannabinoid signaling in synaptosome and cytosolic fractions; b) mass spectrometry-based lipidomics to investigate endocannabinoid levels (eCB). CBD attenuated the increased immobility observed in FSL, compared to FRL in FST, without changing the locomotor behavior in the OFT. In synaptosomes, CBD increased ERK1, mGluR5, and Synaptophysin, but failed to reverse the reduced CB1 and CB2 levels in FSL rats. In the cytosolic fraction, CBD increased ERK2 and decreased mGluR5 expression in FSL rats. Surprisingly, there were no significant changes in eCB levels in response to CBD treatment. These findings suggest that CBD effects in FSL animals are associated with changes in synaptic plasticity markers involving mGluR5, ERK1, ERK2, and synaptophysin signaling in the PFC, without increasing the levels of endocannabinoids in this brain region.

Epigenetic Mechanism of 5-HT/NE/DA Triple Reuptake Inhibitor on Adult Depression Susceptibility in Early Stress Mice

Major depressive disorder (MDD) is a chronic, remitting and debilitating disease and the etiology of MDD is highly complicated that involves genetic and environmental interactions. Despite many pharmacotherapeutic options, many patients remain poorly treated and the development of effective treatments remains a high priority in the field. LPM570065 is a potent 5-hydroxytryptamine (5-HT), norepinephrine (NE) and dopamine (DA) triple reuptake inhibitor and both preclinical and clinical results demonstrate significant efficacy against MDD. This study extends previous findings to examine the effects and underlying mechanisms of LPM570065 on stress vulnerability using a “two-hit” stress mouse model. The “two-hit” stress model used adult mice that had experienced early life maternal separation (MS) stress for social defeat stress (SDS) and then they were evaluated in three behavioral assays: sucrose preference test, tail suspension test and forced swimming test. For the mechanistic studies, methylation-specific differentially expressed genes in mouse hippocampal tissue and ventral tegmental area (VTA) were analyzed by whole-genome transcriptome analysis along with next-generation bisulfite sequencing analysis, followed by RT-PCR and pyrophosphate sequencing to confirm gene expression and methylation. LPM570065 significantly reversed depressive-like behaviors in the mice in the sucrose preference test, the tail suspension test, and the forced swimming test. Morphologically, LPM570065 increased the density of dendritic spines in hippocampal CA1 neurons. Hypermethylation and downregulation of oxytocin receptor (Oxtr) in the hippocampal tissues along with increased protein expression of Dnmt1 and Dnmt3a in mice that experienced the “two-hit” stress compared to those that only experienced adulthood social defeat stress, and LPM570065 could reverse these changes. Combined, these results suggest that methylation specificity of the gene Oxtr in the hippocampus may play an important role in early life stress-induced susceptibility to depression and that the5-HT/NE/DA triple reuptake inhibitor LPM570065 may reduce depression susceptibility via the reversal of the methylation of the gene Oxtr.

Elucidating the Possible Role of FoxO in Depression

Forkhead box-O (FoxO) transcriptional factors perform essential functions in several physiological and biological processes. Recent studies have shown that FoxO is implicated in the pathophysiology of depression. Changes in the upstream mediators of FoxOs including brain-derived neurotrophic factor (BDNF) and protein kinase B have been associated with depressive disorder and the antidepressant agents are known to alter the phosphorylation of FoxOs. Moreover, FoxOs might be regulated by serotonin or noradrenaline signaling and the hypothalamic-pituitary-adrenal (HPA)-axis,both of them are associated with the development of the depressive disorder. FoxO also regulates neural morphology, synaptogenesis, and neurogenesis in the hippocampus, which accounts for the pathogenesis of the depressive disorder. The current article underlined the potential functions of FoxOs in the etiology of depressive disorder and formulate few essential proposals for further investigation. The review also proposes that FoxO and its signal pathway might establish possible therapeutic mediators for the management of depressive disorder.

Quantitative proteomic analysis of cortex in the depressive-like behavior of rats induced by the simulated complex space environment

Long-term spaceflight has always been challenging for astronauts due to the extremely complicated space environmental conditions, including microgravity, noise, confinement, and circadian rhythms disorders, which may cause adverse effects on astronauts' mental health, such as anxiety and depression. Unfortunately, so far, the underlying mechanism is not fully understood. Hence, a novel type of box and rat cage was designed and built in order to simulate complex space environment on the ground. After earth-based simulation for 21 days, the rats exhibited the depressive-like behavior according to the sucrose preference and forced swimming test. We applied label-free quantitative proteomics to explore the molecular mechanisms of depressive-like behavior through global changes in cortical protein abundance, given that the cortex is the hub of emotional management. The results revealed up-regulated spliceosome proteins in contrast to down-regulated oxidative phosphorylation (OXPHOS), glutamatergic, and GABAergic synapse related proteins in the simulated complex space environment (SCSE) group. Furthermore, PSD-95 protein was found down-regulated in mass spectrometry, reflecting its role in the psychopathology of depression, which was further validated by Western blotting. These findings provide valuable information to better understand the mechanisms of depressive-like behavior. SIGNIFICANCE: Quantitative proteomic analysis can quantify differentially abundant proteins related to a variety of potential signaling pathways in the rat cortex in the simulated complex space environment. These findings not only provide valuable information to better understand the mechanisms of depressive-like behavior, but also might offer the potential targets and develop countermeasures for the mental disorders to maintain the health of astronauts during the long-term spaceflight.

Depression-Associated Gene Negr1-Fgfr2 Pathway Is Altered by Antidepressant Treatment

The Negr1 gene has been significantly associated with major depression in genetic studies. Negr1 encodes for a cell adhesion molecule cleaved by the protease Adam10, thus activating Fgfr2 and promoting neuronal spine plasticity. We investigated whether antidepressants modulate the expression of genes belonging to Negr1-Fgfr2 pathway in Flinders sensitive line (FSL) rats, in a corticosterone-treated mouse model of depression, and in mouse primary neurons. Negr1 and Adam10 were the genes mostly affected by antidepressant treatment, and in opposite directions. Negr1 was down-regulated by escitalopram in the hypothalamus of FSL rats, by fluoxetine in the hippocampal dentate gyrus of corticosterone-treated mice, and by nortriptyline in hippocampal primary neurons. Adam10 mRNA was increased by nortriptyline administration in the hypothalamus, by escitalopram in the hippocampus of FSL rats, and by fluoxetine in mouse dorsal dentate gyrus. Similarly, nortriptyline increased Adam10 expression in hippocampal cultures. Fgfr2 expression was increased by nortriptyline in the hypothalamus of FSL rats and in hippocampal neurons. Lsamp, another IgLON family protein, increased in mouse dentate gyrus after fluoxetine treatment. These findings suggest that Negr1-Fgfr2 pathway plays a role in the modulation of synaptic plasticity induced by antidepressant treatment to promote therapeutic efficacy by rearranging connectivity in corticolimbic circuits impaired in depression.

Gene expression signature of antidepressant treatment response/non-response in Flinders Sensitive Line rats subjected to maternal separation

Neurobiological underpinnings of treatment-resistant depression, a debilitating condition associated with significant functional impairment, have not been elucidated. Consequently, the aim of this study was to use animal models of response and resistance to antidepressant treatment, in an attempt to identify differences in associated transcriptional responses. Flinders Sensitive Line rats were subjected to maternal separation (MS) and chronically treated with Escitalopram or Nortriptyline. Antidepressants reduced immobility time in the forced swim test in non-MS rats, while lack of antidepressant behavioural response was observed in MS animals. We developed a novel bioinformatic algorithm that enabled identification of transcriptional signatures in hippocampus and pre-frontal cortex that discriminate vehicle- and antidepressant-treated subjects in both MS and non-MS rats. Functional annotation analysis showed that in antidepressant-responder rats the most enriched pathways included IQGAPs activation, toll-like receptor trafficking, energy metabolism, and regulation of endopeptidase activity. The analysis of interacting proteins implicated synaptic vesicles and neurotransmitter release, ubiquitin regulation, cytoskeleton organisation and carbohydrate metabolism. In contrast, in treatment-resistant MS rats, main expression changes were revealed in ribosomal proteins, inflammatory responses, transcriptional/epigenetic regulation, and small GTPases. Susceptibility signature shared Rtn1, Zdhhc5, Igsf6, and Sim1 genes with the latest depression GWAS meta-analysis, while antidepressant resistance signature shared Ctnnd1, Rbms3, Atp1a3, and Pla2r1 genes. In conclusion, this study demonstrated that distinct transcriptional signatures are associated with behavioural response or non-response to antidepressant treatment. The identification of genes involved in antidepressant response will increase the comprehension of the neurobiological underpinnings of treatment-resistant depression, thus contributing to identification of novel therapeutic targets.

Selecting an Appropriate Animal Model of Depression

Depression has become one of the most severe psychiatric disorders and endangers the health of living beings all over the world. In order to explore the molecular mechanism that underlies depression, different kinds of animal models of depression are used in laboratory experiments. However, a credible and reasonable animal model that is capable of imitating the pathologic mechanism of depression in mankind has yet to be found, resulting in a barrier to further investigation of depression. Nevertheless, it is possible to explain the pathologic mechanism of depression to a great extent by a rational modeling method and behavioral testing. This review aims to provide a reference for researchers by comparing the advantages and disadvantages of some common animal depression models.

Targeting opioid dysregulation in depression for the development of novel therapeutics

Since the serendipitous discovery of the first class of modern antidepressants in the 1950's, all pharmacotherapies approved by the Food and Drug Administration for major depressive disorder (MDD) have shared a common mechanism of action, increased monoaminergic neurotransmission. Despite the widespread availability of antidepressants, as many as 50% of depressed patients are resistant to these conventional therapies. The significant length of time required to produce meaningful symptom relief with these medications, 4-6 weeks, indicates that other mechanisms are likely involved in the pathophysiology of depression which may yield more viable targets for drug development. For decades, no viable candidate target with a different mechanism of action to that of conventional therapies proved successful in clinical studies. Now several exciting avenues for drug development are under intense investigation. One of these emerging targets is modulation of endogenous opioid tone. This review will evaluate preclinical and clinical evidence pertaining to opioid dysregulation in depression, focusing on the role of the endogenous ligands endorphin, enkephalin, dynorphin, and nociceptin/orphanin FQ (N/OFQ) and their respective receptors, mu (MOR), delta (DOR), kappa (KOR), and the N/OFQ receptor (NOP) in mediating behaviors relevant to depression and anxiety. Finally, putative opioid based antidepressants that are under investigation in clinical trials, ALKS5461, JNJ-67953964 (formerly LY2456302 and CERC-501) and BTRX-246040 (formerly LY-2940094) will be discussed. This review will illustrate the potential therapeutic value of targeting opioid dysregulation in developing novel therapies for MDD.

7-Fluoro-1,3-diphenylisoquinoline-1-amine reverses the reduction in self-care behavior induced by maternal separation stress in rats by modulating glutamatergic/GABAergic systems

7-Fluoro-1,3-diphenylisoquinoline-1-amine (FDPI) is a promising isoquinoline that elicits an antidepressant-like action in rodents. In this study, an animal model of stress induced by maternal separation was used to investigate the effects of FDPI in Wistar rats of 30 and 90 days of age. It was investigated the effects of maternal separation in the self-care behavior and the contribution of glutamatergic and gamma-aminobutyric acid (GABA)ergic systems in the FDPI action. Male Wistar rats were separated from their mothers for 3 h/day from postnatal day (PND) 1-10. The rats were treated at different ages (PND-30 and PND-90) with FDPI (5 mg/kg, intragastrically/7 days) and performed the splash test. Maternal separation reduced total grooming time in the splash test, an index of motivational and self-care behavior, and FDPI treatment was effective in reversing this behavior in rats at both ages. The neurochemical parameters were differently affected, dependent on the age of rats, by maternal separation and FDPI. Maternal separation increased the GABA uptake and the excitatory amino acid transporter 1 levels in the prefrontal cortices of rats at PND-30 and FDPI was effective against these alterations. At PND-90, maternal separation decreased the glutamate uptake and increased the GABA uptake and the N-methyl-D-aspartate (NMDA) receptor 2B levels in the prefrontal cortices of rats. FDPI reversed the neurochemical alterations caused by maternal separation in the prefrontal cortices of rats at PND-90. The results of this study demonstrated that FDPI reversed the reduction in self-care behavior induced by maternal separation stress in rats by modulating the glutamatergic/GABAergic systems in rats.

A molluscan extracellular signal-regulated kinase is involved in host response to immune challenges in vivo and in vitro

Extracellular signal-regulated kinases (ERKs) are a group of highly conserved serine/threonine-specific protein kinases that function as important signaling intermediates in mitogen-activated protein kinase (MAPK) pathways, which are involved in a wide variety of cellular activities, including proliferation, inflammation and cytokine production. However, little is known about the roles of this kinase in mollusk immunity. In this study, we identified a molluscan ERK homolog (ChERK) in the Hong Kong oyster (Crassostrea hongkongensis) and investigated its biological functions. The open reading frame (ORF) of ChERK encoded a polypeptide of 365 amino acids, with a predicted molecular weight of 41.96 kDa and pI of 6.43. The predicted ChERK protein contained typical characteristic motifs of the ERK family, including a dual threonine-glutamate-tyrosine (TEY) phosphorylation motif and an ATRW substrate binding site. Phylogenetic analysis revealed that ChERK belonged to the mollusk cluster and shared a close evolutionary relationship with ERK from Crassostrea gigas. In addition, quantitative real-time PCR analysis revealed that ChERK expression was detected in all of the examined tissues and stages of embryonic development; its transcript level was significantly induced upon challenge with bacterial pathogens (Vibrio alginolyticus and Staphylococcus haemolyticus) in vivo and PAMPs (lipopolysaccharide and peptidoglycan) in vitro. Moreover, ChERK was mainly located in the cytoplasm of HEK293T cells. Taken together, these findings may provide novel insights into the functions of molluscan ERKs, especially their roles in response to immune challenge in oyster.

Decreased levels of kynurenic acid in prefrontal cortex in a genetic animal model of depression

OBJECTIVE

There is a growing interest in the role of kynurenine pathway and tryptophan metabolites in the pathophysiology of depression. In the present study, the metabolism of tryptophan along the kynurenine pathway was analysed in a rat model of depression.

METHODS

Kynurenic acid (KYNA) and 3-hydroxykynurenine (3-HK) were measured by high-performance liquid chromatography (HPLC) in prefrontal cortex (PFC) and frontal cortex (FC) in a rat model of depression, the Flinders Sensitive Line (FSL) and their controls, the Flinders Resistant Line (FRL) rats. In addition, KYNA was also measured in hippocampus, striatum and cerebellum.

RESULTS

KYNA levels were reduced in the PFC of FSL rats compared with FRL rats, but did not differ with regard to the FC, hippocampus, striatum or cerebellum. 3-HK levels in PFC and FC, representing the activity of the microglial branch of the kynurenine pathway, did not differ between the FSL and FRL strains.

CONCLUSION

Our results suggest an imbalanced metabolism of the kynurenine pathway in the PFC of FSL rats.

Mitogen-activated protein kinase 1 from disk abalone (Haliotis discus discus): Roles in early development and immunity-related transcriptional responses

Mitogen-activated protein kinase (MAPK) is involved in the regulation of cellular events by mediating signal transduction pathways. MAPK1 is a member of the extracellular-signal regulated kinases (ERKs), playing roles in cell proliferation, differentiation, and development. This is mainly in response to growth factors, mitogens, and many environmental stresses. In the current study, we have characterized the structural features of a homolog of MAPK1 from disk abalone (AbMAPK1). Further, we have unraveled its expressional kinetics against different experimental pathogenic infections or related chemical stimulants. AbMAPK1 harbors a 5' untranslated region (UTR) of 23 bps, a coding sequence of 1104 bps, and a 3' UTR of 448 bp. The putative peptide comprises a predicted molecular mass of 42.2 kDa, with a theoretical pI of 6.28. Based on the in silico analysis, AbMAPK1 possesses two N-glycosylation sites, one S_TK catalytic domain, and a conserved His-Arg-Asp domain (HRD). In addition, a conservative glycine rich ATP-phosphate-binding loop and a threonine-x-tyrosine motif (TEY) important for the autophosphorylation were also identified in the protein. Homology assessment of AbMAPK1 showed several conserved regions, and ark clam (Aplysia californica) showed the highest sequence identity (87.9%). The phylogenetic analysis supported close evolutionary kinship with molluscan orthologs. Constitutive expression of AbMAPK1 was observed in six different tissues of disk abalone, with the highest expression in the digestive tract, followed by the gills and hemocytes. Highest AbMAPK1 mRNA expression level was detected at the trochophore developmental stage, suggesting its role in abalone cell differentiation and proliferation. Significant modulation of AbMAPK1 expression under pathogenic stress suggested its putative involvement in the immune defense mechanism.

Influence of interactions between genes and childhood trauma on refractoriness in psychiatric disorders

Psychiatric disorders are excellent disease models in which gene-environmental interaction play a significant role in the pathogenesis. Childhood trauma has been known as a significant environmental factor in the progress of, and prognosis for psychiatric illness. Patients with refractory illness usually have more severe symptoms, greater disability, lower quality of life and are at greater risk of suicide than other psychiatric patients. Our literature review uncovered some important clinical factors which modulate response to treatment in psychiatric patients who have experienced childhood trauma. Childhood trauma seems to be a critical determinant of treatment refractoriness in psychotic disorder, bipolar disorder, major depressive disorder, and post-traumatic stress disorder. In patients with psychotic disorders, the relationship between childhood trauma and treatment-refractoriness appears to be mediated by cognitive impairment. In the case of bipolar disorder, the relationship appears to be mediated by greater affective disturbance and earlier onset, while in major depressive disorder the mediating factors are persistent, severe symptoms and frequent recurrence. In suicidal individuals, childhood maltreatment was associated with violent suicidal attempts. In the case of PTSD patients, it appears that childhood trauma makes the brain more vulnerable to subsequent trauma, thus resulting in more severe, refractory symptoms. Given that several studies have suggested that there are distinct subtypes of genetic vulnerability to childhood trauma, it is important to understand how gene-environment interactions influence the course of psychiatric illnesses in order to improve therapeutic strategies.

Contribution of NMDA, GABAA and GABAB receptors and l-arginine-NO-cGMP, MEK1/2 and CaMK-II pathways in the antidepressant-like effect of 7-fluoro-1,3-diphenylisoquinoline-1-amine in mice

It has been reported that the antidepressant-like effect of 7-fluoro-1,3-diphenylisoquinoline-1-amine (FDPI) may result from the modulation of brain monoaminergic systems. However, the mechanisms of FDPI action are not fully understood. The aim of this study was to investigate the contribution of N-methyl-d-aspartate (NMDA) and gamma-aminobutyric acid (GABA) systems as well as l-arginine-nitric oxide-(NO)-cyclic guanosine monophosphate-(cGMP), mitogen-activated protein/extracellular signal-regulated kinase (MEK1/2) and Ca(2+)/calmodulin-dependent protein kinase II (CaMK-II) signaling pathways in the antidepressant-like effect of FDPI in the mouse forced swimming test (FST). The levels of NO and uptake of [(3)H]glutamate and [(3)H]GABA were determined in prefrontal cortices of Swiss mice. Pretreatments with NMDA (0.1 pmol/site, i.c.v., a NMDA receptor agonist), bicuculline (1mg/kg, i.p., a GABAA receptor antagonist), phaclofen (2mg/kg, i.p., a GABAB receptor antagonist) and l-arginine (750mg/kg, i.p., a NO precursor), KN-62 (1μg/site, a CaMK-II inhibitor), U0126 (5μg/site, a MEK1/2 inhibitor) and PD09058 (5μg/site, a MEK1/2 inhibitor) blocked the antidepressant-like effect of FDPI, at a dose of 1mg/kg, in the FST. ODQ (30 pmol/site, i.c.v., a soluble guanylate cyclase (sGC) inhibitor) in combination with a sub-effective dose of FDPI (0.1mg/kg, i.g.) reduced the immobility time in the FST. The administration of FDPI (50mg/kg) to mice increased the glutamate uptake and reduced NO levels in the prefrontal cortex of mice. The results suggest a contribution of NMDA, GABAA and GABAB receptors and l-arginine-NO-cGMP pathway in the antidepressant-like action of FDPI in mice, and this effect is related to CaMK-II and MEK 1/2 activation.

Genetic vulnerability, timing of short-term stress and mood regulation: A rodent diffusion tensor imaging study

Early stressful life events predict depression and anxiety in carriers of specific polymorphisms and alter brain responses but brain structural phenotypes are largely unknown. We studied the interaction between short-term stress during specific time-windows and emotion-regulation using a genetic animal model of depression, the Wistar-Kyoto (WKY) rat. Brain structural alterations were analyzed using Diffusion Tensor Imaging (DTI). WKY (n=49) and Wistar (n=55) rats were divided into experimental groups: Early stress (ES): From postnatal day (PND) 27 rats were exposed to three consecutive days of stressors; Late stress (LS): From PND 44 rats were exposed to the same protocol;

CONTROL

No stressors. From PND 50, all animals were behaviorally tested for levels of anxiety and despair-like behaviors and then scanned. Gene×Environment×Timing (G×E×T) interactions (p=0.00022 after Hochberg correction) were found in ventral orbital cortex, cingulate cortex, external capsule, amygdala and dentate gyrus and in the emotion regulation measures. WKY showed longer immobility in forced swim test, but no effect of ES was detected. ES increased open-field anxiety-like behaviors in Wistar rats but not in WKY, possibly indicating a ceiling effect in WKY. Stress in pre-pubertal or adolescent phases in development may influence structural integrity of specific brain regions and emotion regulation behaviors depending on genetic vulnerability, consistent with a G×E×T interaction in mood dysregulation.

Serotonergic signalling suppresses ataxin 3 aggregation and neurotoxicity in animal models of Machado-Joseph disease

Polyglutamine diseases are a class of dominantly inherited neurodegenerative disorders for which there is no effective treatment. Here we provide evidence that activation of serotonergic signalling is beneficial in animal models of Machado-Joseph disease. We identified citalopram, a selective serotonin reuptake inhibitor, in a small molecule screen of FDA-approved drugs that rescued neuronal dysfunction and reduced aggregation using a Caenorhabditis elegans model of mutant ataxin 3-induced neurotoxicity. MOD-5, the C. elegans orthologue of the serotonin transporter and cellular target of citalopram, and the serotonin receptors SER-1 and SER-4 were strong genetic modifiers of ataxin 3 neurotoxicity and necessary for therapeutic efficacy. Moreover, chronic treatment of CMVMJD135 mice with citalopram significantly reduced ataxin 3 neuronal inclusions and astrogliosis, rescued diminished body weight and strikingly ameliorated motor symptoms. These results suggest that small molecule modulation of serotonergic signalling represents a promising therapeutic target for Machado-Joseph disease.

Identification and expression profiles of ERK2 and ERK5 in large yellow croaker (Larimichthys crocea) after temperature stress and immune challenge

Fish is highly affected by many environmental stresses such as temperature and invasive infection. The extracellular signal-regulated kinase (ERK) pathway, part of the mitogen-activated protein kinase (MAPK) family, is found to act as crucial mediators for cell differentiation, proliferation and cell response to various stresses. In the present study, ERK2 (LcERK2) and ERK5 (LcERK2) were cloned and characterized from large yellow croaker, Larimichthys crocea. The full length cDNA sequence of LcERK2 was of 1910 bp, including an ORF of 1110bp encoding a polypeptide of 369 amino acids. The full length cDNA sequence of LcERK5 was of 3720bp, including an ORF of 3375bp encoding a polypeptide of 1124 amino acids. Multiple alignments showed that both LcERK2 and LcERK5 contained highly conserved TEY motif and S_TKc domain in MAPK family and the unique catalytic and active structures of ERK2 and ERK5. Subcellular localization revealed that both LcERK2 and LcERK5 expressed in the cytoplasm and cell nucleus. The expression of LcERK2 and LcERK5 were detected in most tissues of large yellow croaker, with the most predominant expression of LcERK2 in brain and LcERK5 in gill, and the weakest expression of LcERK2 in liver and LcERK5 in intestine, respectively. The expression levels of LcERK2 and LcERK5 after temperature stress and poly I:C and flagellin challenge were investigated in LCK (L. crocea kidney) cells. After temperature stress, significant down-regulations of LcERK2 transcripts were detected after 10 °C stress (p < 0.05) whereas LcERK2 transcripts increased significantly after 35 °C stress (p < 0.05). However, significant down-regulations of LcERK5 expression were detected at most time points after both cold and heat stress (p < 0.05). However, significant up-regulations of LcERK2 and LcERK5 transcripts were found after immune challenge (p < 0.05). Our results showed that LcERK2 transcripts enhanced after heat stress and both LcERK2 and LcERK5 transcripts could be induced by immune challenge. These findings indicated that LcERK2 might be more important in fish response to high temperature stress and both LcERK2 and LcERK5 might play an important role in fish immune response.

Synaptoproteomic analysis of a rat gene-environment model of depression reveals involvement of energy metabolism and cellular remodeling pathways

BACKGROUND

Major depression is a severe mental illness that causes heavy social and economic burdens worldwide. A number of studies have shown that interaction between individual genetic vulnerability and environmental risk factors, such as stress, is crucial in psychiatric pathophysiology. In particular, the experience of stressful events in childhood, such as neglect, abuse, or parental loss, was found to increase the risk for development of depression in adult life. Here, to reproduce the gene x environment interaction, we employed an animal model that combines genetic vulnerability with early-life stress.

METHODS

The Flinders Sensitive Line rats (FSL), a validated genetic animal model of depression, and the Flinders Resistant Line (FRL) rats, their controls, were subjected to a standard protocol of maternal separation (MS) from postnatal days 2 to 14. A basal comparison between the two lines for the outcome of the environmental manipulation was performed at postnatal day 73, when the rats were into adulthood. We carried out a global proteomic analysis of purified synaptic terminals (synaptosomes), in order to study a subcellular compartment enriched in proteins involved in synaptic function. Two-dimensional gel electrophoresis (2-DE), mass spectrometry, and bioinformatic analysis were used to analyze proteins and related functional networks that were modulated by genetic susceptibility (FSL vs. FRL) or by exposure to early-life stress (FRL + MS vs. FRL and FSL + MS vs.

FSL) RESULTS

We found that, at a synaptic level, mainly proteins and molecular pathways related to energy metabolism and cellular remodeling were dysregulated.

CONCLUSIONS

The present results, in line with previous works, suggest that dysfunction of energy metabolism and cytoskeleton dynamics at a synaptic level could be features of stress-related pathologies, in particular major depression.

Early-life exposure to the SSRI paroxetine exacerbates depression-like behavior in anxiety/depression-prone rats

Selective serotonin reuptake inhibitor (SSRI) antidepressants are the mainstay treatment for the 10-20% of pregnant and postpartum women who suffer major depression, but the effects of SSRIs on their children's developing brain and later emotional health are poorly understood. SSRI use during pregnancy can elicit antidepressant withdrawal in newborns and increase toddlers' anxiety and social avoidance. In rodents, perinatal SSRI exposure increases adult depression- and anxiety-like behavior, although certain individuals are more vulnerable to these effects than others. Our study establishes a rodent model of individual differences in susceptibility to perinatal SSRI exposure, utilizing selectively bred Low Responder (bLR) and High Responder (bHR) rats that were previously bred for high versus low behavioral response to novelty. Pregnant bHR/bLR females were chronically treated with the SSRI paroxetine (10 mg/kg/day p.o.) to examine its effects on offspring's emotional behavior and gene expression in the developing brain. Paroxetine treatment had minimal effect on bHR/bLR dams' pregnancy outcomes or maternal behavior. We found that bLR offspring, naturally prone to an inhibited/anxious temperament, were susceptible to behavioral abnormalities associated with perinatal SSRI exposure (which exacerbated their Forced Swim Test immobility), while high risk-taking bHR offspring were resistant. Microarray studies revealed robust perinatal SSRI-induced gene expression changes in the developing bLR hippocampus and amygdala (postnatal days 7-21), including transcripts involved in neurogenesis, synaptic vesicle components, and energy metabolism. These results highlight the bLR/bHR model as a useful tool to explore the neurobiology of individual differences in susceptibility to perinatal SSRI exposure.

Agomelatine: mechanism of action and pharmacological profile in relation to antidepressant properties

Agomelatine behaves both as a potent agonist at melatonin MT1 and MT2 receptors and as a neutral antagonist at 5-HT2C receptors. Accumulating evidence in a broad range of experimental procedures supports the notion that the psychotropic effects of agomelatine are due to the synergy between its melatonergic and 5-hydroxytryptaminergic effects. The recent demonstration of the existence of heteromeric complexes of MT1 and MT2 with 5-HT2C receptors at the cellular level may explain how these two properties of agomelatine translate into a synergistic action that, for example, leads to increases in hippocampal proliferation, maturation and survival through modulation of multiple cellular pathways (increase in trophic factors, synaptic remodelling, glutamate signalling) and key targets (early genes, kinases). The present review focuses on the pharmacological properties of this novel antidepressant. Its mechanism of action, strikingly different from that of conventional classes of antidepressants, opens perspectives towards a better understanding of the physiopathological bases underlying depression.

ERK1/2 phosphorylation is involved in the antidepressant-like action of 2,5-diphenyl-3-(4-fluorophenylseleno)-selenophene in mice

We investigated the antidepressant-like action of 5 compounds belonging to the selenophene class. The involvement of ERK and CREB activation in this action was also demonstrated. In the experiment 1, time-course and dose-response effect of H-DPS, CH3-DPS, Cl-DPS, F-DPS and CF3-DPS were accompanied in the mouse forced swimming test (FST). Firstly, animals received compounds at a dose of 50mg/kg, by intragastric (i.g.) route, at different times (15-240 min) before test. Results showed that the peak of maximum anti-despair behavior induced by Cl-DPS, F-DPS and CF3-DPS was at 30 min; maximum effect of H-DPS and CH3-DPS was found at 60 min, which was maintained until 120 min. Regarding dose-response effect, all compounds reduced immobility time and increased latency for the first episode of immobility at a dose of 50mg/kg. In addition, F-DPS also showed antidepressant-like action at a dose of 25mg/kg, whilst H-DPS, CH3-DPS, Cl-DPS and CF3-DPS were not effective at lower doses. Thus, F-DPS was chosen for further investigation of its mechanism of action. Experiment 2 showed that treatment of animals with F-DPS (50 mg/kg, i.g.) significantly increased phosphorylated ERK1/2 levels in the prefrontal cortex and hippocampus; however, pCREB levels were not affected. Additionally, in the experiment 3 anti-immobility effect of F-DPS was completely blocked by pretreatment of animals with PD 98,059, an inhibitor of ERK phosphorylation, suggesting that ERK signalling activation is involved in its antidepressant-like action in mice. Together our data appoint F-DPS as a promising molecule for the development of a new antidepressant therapy.

Cannabinoids, Neurogenesis and Antidepressant Drugs: Is there a Link?

Similar to clinically used antidepressants, cannabinoids can also regulate anxiety and depressive symptoms. Although the mechanisms of these effects are not completely understood, recent evidence suggests that changes in endocannabinoid system could be involved in some actions of antidepressants. Chronic antidepressant treatment modifies the expression of CB1 receptors and endocannabinoid (EC) content in brain regions related to mood and anxiety control. Moreover, both antidepressant and cannabinoids activate mitogen-activated protein (MAP) kinase and phosphoinositide 3-kinase(PI3-K)/Akt or PKB signaling, intracellular pathways that regulate cell proliferation and neural cell survival. Facilitation of hippocampal neurogenesis is proposed as a common effect of chronic antidepressant treatment. Genetic or pharmacological manipulations of cannabinoid receptors (CB1 and CB2) or enzymes responsible for endocannabinoid-metabolism have also been shown to control proliferation and neurogenesis in the hippocampus. In the present paper we reviewed the studies that have investigated the potential contribution of cannabinoids and neurogenesisto antidepressant effects. Considering the widespread brain distribution of the EC system, a better understanding of this possible interaction could contribute to the development of therapeutic alternatives to mood and anxiety disorders.

Evaluation of the role of MAPK1 and CREB1 polymorphisms on treatment resistance, response and remission in mood disorder patients

Treatment resistant depression (TRD) is a significant clinical and public health problem. Among others, neuroplasticity and inflammatory pathways seem to play a crucial role in the pathomechanisms of antidepressant efficacy. The primary aim of this study was to investigate whether a set of single nucleotide polymorphisms (SNPs) within two genes implicated in neuroplasticity and inflammatory processes (the mitogen activated protein kinase 1, MAPK1 (rs3810608, rs6928, rs13515 and rs8136867), and the cyclic AMP responsive element binding protein 1, CREB1 (rs889895, rs6740584, rs2551922 and rs2254137)) was associated with antidepressant treatment resistance (according to two different definitions), in 285 Major Depressive Disorder (MDD) patients. As secondary aims, we investigated the genetic modulation of the same SNPs on response, remission and other clinical features both in MDD patients and in a larger sample including 82 Bipolar Disorder (BD) patients as well. All patients were screened in the context of a European multicenter project. No association between both the investigated genes and treatment resistance and response was found in MDD patients. However, considering remission, higher rates of CREB1 rs889895 GG genotype were reported in MDD patients. Moreover, MAPK1 rs8136867 AG genotype was found to be associated with remission in the whole sample (MDD and BD). Present results suggest that some genetic polymorphisms in both CREB1 and MAPK1 could be associated with treatment remission. Although further research is needed to draw more definitive conclusions, such results are intriguing since suggest a potential role of two genes implicated in neuroplasticity and inflammatory processes in symptom remission after antidepressant treatment.

Influence of genetic polymorphisms in the glutamatergic and GABAergic systems and their interactions with environmental stressors on antidepressant response

Aim: To investigate the role of genetic polymorphisms in glutamatergic and GABAergic genes and their interactions with environmental stressors in antidepressant response. Methods: A set of 114 SNPs of 34 glutamatergic and GABAergic genes, mainly in promoter and coding regions, were genotyped in 281 Chinese Han major depressive disorder patients. The 17-item Hamilton Depression Rating Scale was used to evaluate the symptom severity and therapeutic efficacy. Childhood Trauma Questionnaire and Life Events Scale were used for assessing early-onset and recent stressful life events, respectively. Results: The single SNPs rs1954787 (GRIK4), rs1992647 (GABRA6), rs10036156 (GABRP) and rs3810651 (GABRQ) were significantly associated with antidepressant response, as were haplotypes in GRIK4 and GABRP genes. A genetic interaction between rs11542313 (GAD1), rs13303344 (GABRD) and rs2256882 (GABRE) was identified as impacting therapeutic response. SNPs in GRIA3 demonstrated interactions with early-onset adverse events and recent negative life stress that influence treatment outcome. Conclusion: Genetic polymorphisms in the glutamatergic and GABAergic systems and certain genetic interactions, as well as gene–environment interactions, are associated with antidepressant response.

Original submitted 9 July 2012; Revision submitted 1 January 2013

Altered functional protein networks in the prefrontal cortex and amygdala of victims of suicide

Probing molecular brain mechanisms related to increased suicide risk is an important issue in biological psychiatry research. Gene expression studies on post mortem brains indicate extensive changes prior to a successful suicide attempt; however, proteomic studies are scarce. Thus, we performed a DIGE proteomic analysis of post mortem tissue samples from the prefrontal cortex and amygdala of suicide victims to identify protein changes and biomarker candidates of suicide. Among our matched spots we found 46 and 16 significant differences in the prefrontal cortex and amygdala, respectively; by using the industry standard t test and 1.3 fold change as cut off for significance. Because of the risk of false discoveries (FDR) in these data, we also made FDR adjustment by calculating the q-values for all the t tests performed and by using 0.06 and 0.4 as alpha thresholds we reduced the number of significant spots to 27 and 9 respectively. From these we identified 59 proteins in the cortex and 11 proteins in the amygdala. These proteins are related to biological functions and structures such as metabolism, the redox system, the cytoskeleton, synaptic function, and proteolysis. Thirteen of these proteins (CBR1, DPYSL2, EFHD2, FKBP4, GFAP, GLUL, HSPA8, NEFL, NEFM, PGAM1, PRDX6, SELENBP1 and VIM,) have already been suggested to be biomarkers of psychiatric disorders at protein or genome level. We also pointed out 9 proteins that changed in both the amygdala and the cortex, and from these, GFAP, INA, NEFL, NEFM and TUBA1 are interacting cytoskeletal proteins that have a functional connection to glutamate, GABA, and serotonin receptors. Moreover, ACTB, CTSD and GFAP displayed opposite changes in the two examined brain structures that might be a suitable characteristic for brain imaging studies. The opposite changes of ACTB, CTSD and GFAP in the two brain structures were validated by western blot analysis.

Maternal separation enhances object location memory and prevents exercise-induced MAPK/ERK signalling in adult Sprague-Dawley rats

Early life stress increases the risk of developing psychopathology accompanied by reduced cognitive function in later life. Maternal separation induces anxiety-like behaviours and is associated with impaired memory. On the other hand, exercise has been shown to diminish anxiety-like behaviours and improve cognitive function. The effects of maternal separation and exercise on anxiety, memory and hippocampal proteins were investigated in male Sprague-Dawley rats. Maternal separation produced anxiety-like behaviours which were reversed by exercise. Maternal separation also enhanced object location memory which was not affected by exercise. Exercise did, however, increase synaptophysin and phospho-extracellular signal-regulated kinase (p-ERK) in the hippocampus of non-separated rats and this effect was not observed in maternally separated rats. These findings show that maternal separation selectively enhanced n memory and prevented activation of the MAPK/ERK signalling pathway in the adult rat hippocampus.

5-HT2 ligands in the treatment of anxiety and depression

INTRODUCTION

One third of depressed patients do not respond adequately to conventional antidepressants including the selective serotonin reuptake inhibitors (SSRIs). Therefore, multi-target drugs or augmentation strategies have been developed for the management of SSRIs-resistant patients. In this context, the 5-HT(2) receptor subtypes represent promising targets but their precise roles have yet to be determined.

AREAS COVERED

The aim of this review is to shed some light on the preclinical evidence supporting the use of 5-HT(2A) and/or 5-HT(2C) receptor antagonists such as antipsychotics, as potential effective adjuncts in SSRIs-resistant depression. This review synthesizes the current literature about the behavioral, electrophysiological and neurochemical effects of 5-HT(2) receptors ligands on the monoaminergic systems but also on adult hippocampal neurogenesis.

EXPERT OPINION

Although studies support the hypothesis that the inactivation of 5-HT(2A) and/or 5-HT(2C) receptors might be of interest to reinforce different facets of the therapeutic activity of SSRIs, this pharmacological strategy remains debatable notably because of the lack of chronic data in relevant animal models. Conversely, emerging evidence suggests that the activation of 5-HT(2B) receptor is required for antidepressant-like activity, opening the way to new therapeutic approaches. However, the potential risks related to the enhancement of monoaminergic neurotransmissions could represent a major concern.

Long-lasting effects of chronic rTMS to treat chronic rodent model of depression

Repetitive transcranial magnetic stimulation (rTMS) has been demonstrated in the pre-clinical and clinical settings to have an antidepressant effect. However, studies on the long-lasting effect of rTMS, especially when the effect is measured after treatment has ceased for a few weeks is lacking. We examined this question in a chronic unpredicted mild stress (CUMS) rat model of depression. We gave 3 weeks of high frequency (15 Hz) rTMS, venlafaxine, or these two treatments combined to a modified CUMS paradigm, and then investigated the prolonged effect of treatments. Behavioral testing (sucrose preference test, open field test, forced swimming test, novelty suppressed feeding test), plasma hormone level, hippocampal BrdU labeling, and amount of related neurotropic factors were used to assess the effects of stress and treatments. Long-term chronic rTMS significantly reversed andehonic-like behavior, increased hippocampus cell proliferation, BDNF protein level, phosphorylation of ERK1/2 compared with CUMS rats two weeks after the cessation of rTMS treatment. However, the changes in plasma hormone level were not sustained for that amount of time. Venlafaxine had no interaction with the physical stimulation. Our results suggest that high frequency rTMS has long-lasting effects, which may have some relationship with neuroplasticity.

Influence and interaction of genetic polymorphisms in the serotonin system and life stress on antidepressant drug response

Variation in genes implicated in serotonin neurotransmission may interact with environmental factors to influence antidepressant response. We aimed to determine how a range of polymorphisms in serotonergic genes determine this response to treatment and how they interact with childhood trauma and recent life stress in a Chinese sample. In total, 14 single nucleotide polymorphisms (SNPs) in coding regions of 10 serotonergic genes (HTR1A, HTR1B, HTR1D, HTR2A, HTR3A, HTR3C, HTR3D, HTR3E, HTR5A and TPH2) were genotyped in 308 Chinese Han patients with major depressive disorder. Response to 6 weeks' antidepressant treatment was determined by change in the 17-item Hamilton Depression Rating Scale (HDRS-17) score, and previous stressful events were evaluated by the Life Events Scale (LES) and Childhood Trauma Questionnaire-Short Form (CTQ-SF). Two 5-HT1B receptor SNPs (rs6296 and rs6298) and one tryptophan hydroxylase2 (rs7305115) SNP were significantly associated with antidepressant response in this Chinese sample, as was a haplotype in TPH2 (rs7305115 and rs4290270). A gene-gene interaction on antidepressant response was found between SNPs in HTR1B, HTR3A and HTR5A in female subjects. The HTR1B SNPs demonstrated interaction with recent stress, while that for TPH2 interacted with childhood trauma to influence antidepressant response.

Genetic variation in the calcium/calmodulin-dependent protein kinase (CaMK) pathway is associated with antidepressant response in females

OBJECTIVE

Antidepressant effects on monoamine neurotransmission may be influenced by genetic variation in intracellular signal transduction pathways, such as the cyclic adenosine monophosphate (cAMP)--protein kinase A (PKA) pathway, Ras-mitogen activated protein kinase (MAPK) pathway and calcium/calmodulin-dependent protein kinase (CaMK) pathway. The aims of this study were to examine the association of polymorphisms in candidate genes of these three signal transduction pathways with response to antidepressant treatment, and to determine the effects of, and interactions with, environment factors.

METHODS

We recruited 412 patients who met diagnosis criteria for major depressive disorder (MDD) (DSM-IV Axis I). 284 patients completed 8 weeks treatment with selective serotonin reuptake inhibitors (SSRIs) or serotonin and noradrenergic reuptake inhibitors (SNRIs). Severity of depression was measured with the Hamilton Depression Rating Scale (HDRS) before and after 8 weeks antidepressant treatment. 209 patients completed the Childhood Trauma Questionnaire, 28 item Short Form (CTQ-SF) which was used to evaluate childhood adverse events. 218 patients completed the Life Events Scale (LES) which were used to evaluate life stress before onset. 155 SNPs in 66 candidate genes were genotyping by Illumina GoldenGate, including 28 SNPs in 15 genes of cAMP-PKA pathway, 37 SNPs in 17 genes of Ras-MAPK pathway and 90 SNPs in 34 genes of CaMK pathway. The remission criterion was HDRS score equal to or less than 7. Single SNP and haplotype associations were analyzed by UNPHASED 3.3.13. Gene-environment interactions were analyzed by binary logistic regression with SPSS 11.0 software.

RESULTS

The rs2230372 SNP in ITPR2, rs2280272 in PRKCZ, rs17109671, and rs17109674 in PLCE1 were significant associated with remission, as were haplotypes in PRKCZ and PLCE1. All these positive associations were found in genes of the CaMK pathway, but not the cAMP-PKA or Ras-MAPK pathways. There were no significant differences in CTQ scores and LES scores between remitters and non-remitters. No significantly interactions between candidate genes and environment effects were observed.

CONCLUSION

The CaMK pathway may be important in determining antidepressant response. But recent adverse life events, childhood adversity, and interactions between candidate genes and environment factors appear not to influence short term antidepressant outcome.

Escitalopram, an antidepressant with an allosteric effect at the serotonin transporter--a review of current understanding of its mechanism of action

RATIONALE

Escitalopram is a widely used antidepressant for the treatment of patients with major depression. It is the pure S-enantiomer of racemic citalopram. Several clinical trials and meta-analyses indicate that escitalopram is quantitatively more efficacious than many other antidepressants with a faster onset of action.

OBJECTIVE

This paper reviews current knowledge about the mechanism of action of escitalopram.

RESULTS

The primary target for escitalopram is the serotonin transporter (SERT), which is responsible for serotonin (or 5-hydroxytryptamine [5-HT]) reuptake at the terminals and cell bodies of serotonergic neurons. Escitalopram and selective serotonin reuptake inhibitors bind with high affinity to the 5-HT binding site (orthosteric site) on the transporter. This leads to antidepressant effects by increasing extracellular 5-HT levels which enhance 5-HT neurotransmission. SERT also has one or more allosteric sites, binding to which modulates activity at the orthosteric binding site but does not directly affect 5-HT reuptake by the transporter. In vitro studies have shown that through allosteric binding, escitalopram decreases its own dissociation rate from the orthosteric site on the SERT. R-citalopram, the nontherapeutic enantiomer in citalopram, is also an allosteric modulator of SERT but can inhibit the actions of escitalopram by interfering negatively with its binding. Both nonclinical studies and some clinical investigations have demonstrated the cellular, neurochemical, neuroadaptive, and neuroplastic changes induced by escitalopram with acute and chronic administration.

CONCLUSIONS

The findings from binding, neurochemical, and neurophysiological studies may provide a mechanistic rationale for the clinical difference observed with escitalopram compared to other antidepressant therapies.

Animal models of depression vulnerability

The rapid increase in the number of proposed animal models of depression reflects the dissatisfaction with our current state of knowledge on neurobiology of depression and unsuccessful drug development. Results obtained with even the best validated models can be difficult to compare. Because evidence from epidemiological studies suggests that depression occurs in biologically predisposed subjects under the impact of adverse life events, increasing attempts have been made to use the diathesis-stress concept in animal models. In this way, factors underpinning vulnerability to depression have been identified by measuring behavioural traits analogous to facets of human personality, or created by inducing neurochemical lesions. Stressful interventions administered prenatally, in early life or in adulthood have been combined with other vulnerability factors including genetic changes. As a result, several putative animal models of endophenotypes of depression or depression vulnerability have been proposed. Diathesis-stress models may aid in separating adaptive and maladaptive strategies in coping with stress, and understanding the relevant neurobiology. Studies comparing effects of stress on males and females should reveal to which extent the pathogenetic processes leading to depression can be specific to sex/gender.

Selectively bred rodents as models of depression and anxiety

Stress related diseases such as depression and anxiety have a high degree of co morbidity, and represent one of the greatest therapeutic challenges for the twenty-first century. The present chapter will summarize existing rodent models for research in psychiatry, mimicking depression- and anxiety-related diseases. In particular we will highlight the use of selective breeding of rodents for extremes in stress-related behavior. We will summarize major behavioral, neuroendocrine and neuronal parameters, and pharmacological interventions, assessed in great detail in two rat model systems: The Flinders Sensitive and Flinders Resistant Line rats (FSL/FRL model), and rats selectively bred for high (HAB) or low (LAB) anxiety related behavior (HAB/LAB model). Selectively bred rodents also provide an excellent tool in order to study gene and environment interactions. Although it is generally accepted that genes and environmental factors determine the etiology of mental disorders, precise information is limited: How rigid is the genetic disposition? How do genetic, prenatal and postnatal influences interact to shape adult disease? Does the genetic predisposition determine the vulnerability to prenatal and postnatal or adult stressors? In combination with modern neurobiological methods, these models are important to elucidate the etiology and pathophysiology of anxiety and affective disorders, and to assist in the development of new treatment paradigms.

Influence and interaction of genetic polymorphisms in catecholamine neurotransmitter systems and early life stress on antidepressant drug response

BACKGROUND

Catecholamine neurotransmission plays an important role in major depression. Variation in genes implicated in the synthesis and signal transduction of catecholamines (norepinephrine and dopamine) may interact with environmental factors to affect the outcome of antidepressant treatment. We aimed to determine how a range of polymorphisms in noradrenergic and dopaminergic genes influence this response to treatment and how they interact with childhood trauma and recent life stress in a Chinese sample.

METHODS

In a sample of 308 Chinese Han patients with major depressive disorder, 13 single nucleotide polymorphisms (SNPs) in coding regions of six genes (MAOA, SLC6A2, TH, COMT, DRD2, DRD3) with minor allele frequencies >5% were successfully genotyped from an initial series of 35 SNPs in 11 candidate genes associated with catecholamine neurotransmission. The responses to 6 weeks' treatment with antidepressant drugs was determined by changes in the 17-item Hamilton Depression Rating Scale (HAMD-17) score, and previous stressful events were evaluated by the Life Events Scale (LES) and Childhood Trauma Questionnaire-Short Form (CTQ-SF). Single SNP and haplotype associations with treatment response were analysed by UNPHASED 3.0.13, gene-gene interactions were analysed by generalized multifactor dimensionality reduction (GMDR) and gene-environment interactions by logistic regression.

RESULTS

A haplotype in MAOA (rs1137070 and rs6323) was significantly associated with antidepressant response in the total group, the nonSSRI subgroup and the female subgroup. Two haplotypes in COMT (involving rs4633, rs4818 and rs769224) were significantly associated with antidepressant response in the nonSSRI subgroup. The SLC6A2 SNPs interacted with childhood trauma to influence antidepressant response.

CONCLUSIONS

A haplotype in MAOA and two haplotypes in COMT are found to be associated with antidepressant treatment response in this sample. Stressors in early life may interact with polymorphisms in SLC6A2 to influence response to antidepressant treatment.

Abnormalities in α/β-CaMKII and related mechanisms suggest synaptic dysfunction in hippocampus of LPA1 receptor knockout mice

Lysophosphatidic acid (LPA) is a natural lysophospholipid that regulates neuronal maturation. In mice, the deletion of the LPA1 receptor causes some phenotypic defects partly overlapping with those found in schizophrenia. In this study, we identified molecular abnormalities in hippocampal synaptic mechanisms involved in glutamatergic neurotransmission, which allow further characterization of synaptic aberrations in LPA1 knockout (KO) mice. At the synaptic level, we found dysregulation of Ca2+/calmodulin (CaM)-dependent kinase II (CaMKII) activity and phosphorylation, with markedly higher Ca2+-dependent kinase activity, probably related to increased expression levels of the β isoform of CaMKII. Conversely, although the synaptic Ca2+-independent activity of the enzyme was unchanged, autophosphorylation levels of both α and β isoforms were significantly increased in LPA1 KO mice. Moreover, in LPA1 KO mice the α/β isoform ratio of CaMKII, which plays a key role in neuronal maturation during development, was markedly decreased, as found previously in schizophrenia patients. At post-synaptic level, LPA1 KO mice showed changes in expression, phosphorylation and interactions of NMDA and AMPA receptor subunits that are consistent with basal strengthening of glutamatergic synapses. However, we measured a reduction of nuclear cAMP responsive element-binding protein phosphorylation, suggesting that activation of the NMDA receptor does not occur at the intracellular signalling level. At the presynaptic level, in line with previous evidence from schizophrenia patients and animal models of pathology, LPA1 KO mice showed accumulation of SNARE protein complexes. This study shows that CaMKII and related synaptic mechanisms at glutamatergic synapses are strongly dysregulated in LPA1 KO mice.

Animal models of depression and anxiety: What do they tell us about human condition?

While modern neurobiology methods are necessary they are not sufficient to elucidate etiology and pathophysiology of affective disorders and develop new treatments. Achievement of these goals is contingent on applying cutting edge methods on appropriate disease models. In this review, the authors present four rodent models with good face-, construct-, and predictive-validity: the Flinders Sensitive rat line (FSL); the genetically "anxious" High Anxiety-like Behavior (HAB) line; the serotonin transporter knockout 5-HTT(-/-) rat and mouse lines; and the post-traumatic stress disorder (PTSD) model induced by exposure to predator scent, that they have employed to investigate the nature of depression and anxiety.

Escitalopram affects cytoskeleton and synaptic plasticity pathways in a rat gene-environment interaction model of depression as revealed by proteomics. Part II: environmental challenge

Large-scale investigations aimed at elucidating the molecular mechanism of action of antidepressant treatment are achievable through the application of proteomic technologies. We performed a proteomic study on the Flinders Sensitive Line (FSL), a genetically selected rat model of depression, and the control Flinders Resistant Line (FRL). To evaluate gene-environment interactions, FSL and FRL animals were separated from their mothers for 3 h from postnatal days 2 to 14 (maternal separation; MS), since early-life trauma is considered an important antecedent of depression. All groups received either escitalopram (Esc) admixed to food pellets (25 mg/kg.d) or vehicle for 1 month. Protein extracts from prefrontal/frontal cortex and hippocampus were separated by 2D electrophoresis. Proteins differentially modulated were identified by mass spectrometry. Bioinformatics analyses were performed to discover gene ontology terms associated with the modulated proteins. This paper was focused on the modifications induced by the environmental challenge of MS, both on the predisposed genetic background and on the resistant phenotype. The combination between Esc treatment and MS was investigated by comparing the MS, Esc-treated rats with rats subjected to each single procedure. In MS rats, antidepressant treatment influenced mainly proteins involved in carbohydrate metabolism in FSL rats and in vesicle-mediated transport in FRL rats. When studying the interaction between Esc and MS vs. non-separated rats, proteins playing a role in cytoskeleton organization, neuronal development, vesicle-mediated transport and synaptic plasticity were identified. The results provide further support to the available reports that antidepressant treatment affects intracellular pathways and also suggest new potential targets for future therapeutic intervention.

Gene-environment interactions: early life stress and risk for depressive and anxiety disorders

RATIONALE

Prior reviews have examined how stress, broadly defined, interacts with genetic diathesis in the pathogenesis of internalizing (i.e., depressive and anxiety) disorders. Recent findings have suggested a unique role for early life stress (ELS) in the development of internalizing disorders, contributing to the rapid proliferation of research in this area.

OBJECTIVE

This paper critically reviews studies in humans examining gene-environment interaction (GxE) effects of ELS on the risk for depression and anxiety, primarily from a candidate gene perspective. Major methodological challenges that are unique to such studies are considered.

RESULTS

The majority of published studies have focused on candidates that regulate the serotonin system, especially the serotonin transporter. More recent work has addressed interactions of ELS with candidates from the hypothalamic-pituitary-adrenal axis and neurotrophin system. Available studies vary greatly with respect to definitions of ELS, examination of gene-gene interactions, consideration of gender effects, and attention to analytic limitations.

CONCLUSIONS

Overall, there is support for GxE effects of ELS on the risk for depressive and anxiety outcomes. Future studies of ELS in this context will require careful attention to methodologic considerations. Such studies would benefit from more systematic assessment of positive environmental factors (e.g., social support) and greater utilization of developmentally sensitive paradigms.

Chronic escitalopram treatment restores spatial learning, monoamine levels, and hippocampal long-term potentiation in an animal model of depression

RATIONALE

The neural basis of depression-associated cognitive impairment remains poorly understood, and the effect of antidepressants on learning and synaptic plasticity in animal models of depression is unknown. In our previous study, learning was impaired in the neonatal clomipramine model of endogenous depression. However, it is not known whether the cognitive impairment in this model responds to antidepressant treatment, and the electrophysiological and neurochemical bases remain to be determined.

OBJECTIVES

To address this, we assessed the effects of escitalopram treatment on spatial learning and memory in the partially baited radial arm maze (RAM) task and long-term potentiation (LTP) in the Schaffer collateral-CA1 synapses in neonatal clomipramine-exposed rats. Also, alterations in the levels of biogenic amines and acetylcholinesterase (AChE) activity were estimated.

RESULTS

Fourteen days of escitalopram treatment restored the mobility and preference to sucrose water in the forced swim and sucrose consumption tests, respectively. The learning impairment in the RAM was reversed by escitalopram treatment. Interestingly, CA1-LTP was decreased in the neonatal clomipramine-exposed rats, which was restored by escitalopram treatment. Monoamine levels and AChE activity were decreased in several brain regions, which were restored by chronic escitalopram treatment.

CONCLUSIONS

Thus, we demonstrate that hippocampal LTP is decreased in this animal model of depression, possibly explaining the learning deficits. Further, the reversal of learning and electrophysiological impairments by escitalopram reveals the important therapeutic effects of escitalopram that could benefit patients suffering from depression.

Sidedness of the ATP-Na+-K+ interactions with the Na+ pump in squid axons

Using dialysed squid axons we have been able to control internal and external ionic compositions under conditions in which most of the Na+ efflux goes through the Na+ pump. We found that (i) internal K+ had a strong inhibitory effect on Na+ efflux; this effect was antagonized by ATP, with low affinity, and by internal Na+, (ii) a reduction in ATP levels from 3 mM to 50 microM greatly increased the apparent affinity for external K+, but reduced its effectiveness compared with other monovalent cations, as an activator of Na+ efflux, and (iii) the relative effectiveness of different K+ congeners as external activator of the Na+ efflux, though affected by the ATP concentration, was not affected by the Na+/K+ ratio inside the cells. These results are consistent with the idea that the same conformation of the (Na+ + K+)-ATPase can be reached by interaction with external K+ after phosphorylation and with internal K+ before rephosphorylation. They also stress a nonphosphorylating regulatory role of ATP.