The role of CREB and other transcription factors in the pharmacotherapy and etiology of depression

Brain and blood transcriptome profiles delineate common genetic pathways across suicidal ideation and suicide

Human genetic studies indicate that suicidal ideation and behavior are both heritable. Most studies have examined associations between aberrant gene expression and suicide behavior, but behavior risk is linked to the severity of suicidal ideation. Through a gene network approach, this study investigates how gene co-expression patterns are associated with suicidal ideation and severity using RNA-seq data in peripheral blood from 46 live participants with elevated suicidal ideation and 46 with no ideation. Associations with the presence of suicidal ideation were found within 18 co-expressed modules (p < 0.05), as well as in 3 co-expressed modules associated with suicidal ideation severity (p < 0.05, not explained by severity of depression). Suicidal ideation presence and severity-related gene modules with enrichment of genes involved in defense against microbial infection, inflammation, and adaptive immune response were identified and investigated using RNA-seq data from postmortem brain that revealed gene expression differences with moderate effect sizes in suicide decedents vs. non-suicides in white matter, but not gray matter. Findings support a role of brain and peripheral blood inflammation in suicide risk, showing that suicidal ideation presence and severity are associated with an inflammatory signature detectable in blood and brain, indicating a biological continuity between ideation and suicidal behavior that may underlie a common heritability.

Insights into the neurobiology of suicidality: explicating the role of glutamatergic systems through the lens of ketamine

Suicidality is a prevalent mental health condition, and managing suicidal patients is one of the most challenging tasks for health care professionals due to the lack of rapid-acting, effective psychopharmacological treatment options. According to the literature, suicide has neurobiological underpinnings that are not fully understood, and current treatments for suicidal tendencies have considerable limitations. To treat suicidality and prevent suicide, new treatments are required; to achieve this, the neurobiological processes underlying suicidal behavior must be thoroughly investigated. Although multiple neurotransmitter systems, particularly serotonergic systems, have been studied in the past, less has been reported in relation to disruptions in glutamatergic neurotransmission, neuronal plasticity, and neurogenesis that result from stress-related abnormalities of the hypothalamic-pituitary-adrenal system. Informed by the literature, which reports robust antisuicidal and antidepressive properties of subanaesthetic doses of ketamine, this review aims to provide an examination of the neurobiology of suicidality (and relevant mood disorders) with implications of pertinent animal, clinical, and postmortem studies. We discuss dysfunctions in the glutamatergic system, which may play a role in the neuropathology of suicidality and the role of ketamine in restoring synaptic connectivity at the molecular levels.

Imbalance of multiple neurotransmitter pathways leading to depression-like behavior and cognitive dysfunction in the triple transgenic mouse model of Alzheimer disease

Depression is among the most frequent psychiatric comorbid conditions in Alzheimer disease (AD). However, pharmacotherapy for depressive disorders in AD is still a big challenge, and the data on the efffcacy of current antidepressants used clinically for depressive symptoms in patients with AD remain inconclusive. Here we investigated the mechanism of the interactions between depression and AD, which we believe would aid in the development of pharmacological therapeutics for the comorbidity of depression and AD. Female APP/PS1/Tau triple transgenic (3×Tg-AD) mice at 24 months of age and age- and sex-matched wild-type (WT) mice were used. The shuttle-box passive avoidance test (PAT) were implemented to assess the abilities of learning and memory, and the open field test (OFT) and the tail suspension test (TST) were used to assess depression-like behavior. High-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) was used to detect the level of neurotransmitters related to depression in the hippocampus of mice. The data was identified by orthogonal projections to latent structures discriminant analysis (OPLS-DA). Most neurotransmitters exert their effects by binding to the corresponding receptor, so the expression of relative receptors in the hippocampus of mice was detected using Western blot. Compared to WT mice, 3×Tg-AD mice displayed significant cognitive impairment in the PAT and depression-like behavior in the OFT and TST. They also showed significant decreases in the levels of L-tyrosine, norepinephrine, vanillylmandelic acid, 5-hydroxytryptamine, and acetylcholine, in contrast to significant increases in 5-hydroxyindoleacetic acid, L-histidine, L-glutamine, and L-arginine in the hippocampus. Moreover, the expression of the alpha 1a adrenergic receptor (ADRA1A), serotonin 1 A receptor (5HT1A), and γ-aminobutyric acid A receptor subunit alpha-2 (GABRA2) was significantly downregulated in the hippocampus of 3×Tg-AD mice, while histamine H3 receptor (H3R) expression was significantly upregulated. In addition, the ratio of phosphorylated cAMP-response element-binding protein (pCREB) and CREB was significantly decreased in the hippocampus of 3×Tg-AD mice than WT mice. We demonstrated in the present study that aged female 3×Tg-AD mice showed depression-like behavior accompanied with cognitive dysfunction. The complex and diverse mechanism appears not only relevant to the imbalance of multiple neurotransmitter pathways, including the transmitters and receptors of the monoaminergic, GABAergic, histaminergic, and cholinergic systems, but also related to the changes in L-arginine and CREB signaling molecules.

Functional Architecture of Brain and Blood Transcriptome Delineate Biological Continuity Between Suicidal Ideation and Suicide

Human genetic studies indicate that suicidal ideation and behavior are both heritable. Most studies have examined associations between aberrant gene expression and suicide behavior, but behavior risk is linked to severity of suicidal ideation. Through a gene network approach, this study investigates how gene co-expression patterns are associated with suicidal ideation and severity using RNA-seq data in peripheral blood from 46 live participants with elevated suicidal ideation and 46 with no ideation. Associations with presence and severity of suicidal ideation were found within 18 and 3 co-expressed modules respectively (p < 0.05), not explained by severity of depression. Suicidal ideation presence and severity-related gene modules with enrichment of genes involved in defense against microbial infection, inflammation, and adaptive immune response were identified, and tested using RNA-seq data from postmortem brain that revealed gene expression differences in suicide decedents vs. non-suicides in white matter, but not gray matter. Findings support a role of brain and peripheral blood inflammation in suicide risk, showing that suicidal ideation presence and severity is associated with an inflammatory signature detectable in blood and brain, indicating a biological continuity between ideation and suicidal behavior that may underlie a common heritability.

Dihydromyricetin Attenuates Depressive-like Behaviors in Mice by Inhibiting the AGE-RAGE Signaling Pathway

Depression is a complex mental disorder, affecting approximately 280 million individuals globally. The pathobiology of depression is not fully understood, and the development of new treatments is urgently needed. Dihydromyricetin (DHM) is a natural flavanone, mainly distributed in Ampelopsis grossedentata. DHM has demonstrated a protective role against cardiovascular disease, diabetes, liver disease, cancer, kidney injury and neurodegenerative disorders. In the present study, we examined the protective effect of DHM against depression in a chronic depression mouse model induced by corticosterone (CORT). Animals exposed to CORT displayed depressive-like behaviors; DHM treatment reversed these behaviors. Network pharmacology analyses showed that DHM's function against depression involved a wide range of targets and signaling pathways, among which the inflammation-linked targets and signaling pathways were critical. Western blotting showed that CORT-treated animals had significantly increased levels of the advanced glycation end product (AGE) and receptor of AGE (RAGE) in the hippocampus, implicating activation of the AGE-RAGE signaling pathway. Furthermore, enzyme-linked immunosorbent assay (ELISA) detected a marked increase in the production of proinflammatory cytokines, interleukin-1 beta (IL-1β), IL-6 and tumor necrosis factor-alpha (TNFα) in the hippocampus of CORT-treated mice. DHM administration significantly counteracted these CORT-induced changes. These findings suggest that protection against depression by DHM is mediated by suppression of neuroinflammation, predominantly via the AGE-RAGE signaling pathway.

Immune transcriptional profiles in mothers with clinically elevated depression and anxiety symptoms several years post-delivery

BACKGROUND

Most research on maternal mental health focuses on the perinatal period and does not extend beyond 12 months postpartum. However, emerging evidence suggests that for some women (30%-50%), psychological symptoms may persist beyond the first year postpartum or even emerge later increasing the risk of chronic mood and anxiety symptoms. Despite the high prevalence rates and devastating maternal-child consequences, studies examining maternal depression, anxiety, and post-traumatic stress disorder (PTSD) beyond the first year postpartum are rare and our understanding of the underlying biological mechanisms is incomplete. Inflammatory processes are thought to be involved in the pathophysiology of depression, anxiety, & PTSD outside of the postpartum period. Therefore, the purpose of the current investigation was to examine the relationship between depression, anxiety, and PTSD two to three years post-delivery, and transcriptional control pathways relevant to inflammatory and antiviral processes.

METHODS

Women over 18 years of age enrolled in ongoing research studies at Cedars Sinai Medical Center who were 2-3 years postpartum were invited to participate in the current study. Women (N = 33) reported on their levels of depression, anxiety, and PTSD and provided a blood sample approximately 2-3 years post-delivery. Bioinformatic analyses of differential gene expression (DGEs) to infer transcription factor activity were used. Gene expression was assayed by RNA sequencing and TELiS bioinformatics analysis of transcription factor-binding motifs in the promoters of differentially expressed genes.

RESULTS

DGE analyses revealed that women with clinically elevated symptoms of depression, anxiety and PTSD (n = 16) showed upregulation of genes activated by transcription control pathways associated with inflammation (NF-_Κ B, p = 0.004; JUN, p = 0.02), including ꞵ-adrenergic responsive CREB (p = 0.01) and reduced activation of genes associated with the antiviral response (IRFs, p = 0.02) and the glucocorticoid signaling pathway (GR, p = 0.02) compared to women without clinical symptoms (n = 17).

CONCLUSIONS

This is one of the first investigations into the immune signaling pathways involved in depression, anxiety, and PTSD two to three years post-delivery. The results of this study suggest that clinically elevated symptoms of depression, anxiety, and PTSD two to three years post-delivery are associated with a gene expression profile characterized by upregulated expression of pro-inflammatory genes and downregulated expression of antiviral genes. The data also point to two potential stress responsive pathways linking symptoms to increased inflammatory signaling in immune cells: sympathetic nervous system mediated ꞵ-adrenergic signaling and reduced hypothalamic pituitary adrenal axis activity. Together, these findings highlight the need for investigations into maternal mental health beyond the first year postpartum. This article is protected by copyright. All rights reserved.

Farnesoid X Receptor-Mediated Cytoplasmic Translocation of CRTC2 Disrupts CREB-BDNF Signaling in Hippocampal CA1 and Leads to the Development of Depression-Like Behaviors in Mice

BACKGROUND

We recently identified neuronal expression of farnesoid X receptor (FXR), a bile acid receptor known to impair autophagy by inhibiting cyclic adenosine monophosphate response element-binding protein (CREB), a protein whose underfunctioning is linked to neuroplasticity and depression. In this study, we hypothesize that FXR may mediate depression via a CREB-dependent mechanism.

METHODS

Depression was induced in male C57BL6/J mice via chronic unpredictable stress (CUS). Subjects underwent behavioral testing to identify depression-like behaviors. A variety of molecular biology techniques, including viral-mediated gene transfer, Western blot, co-immunoprecipitation, and immunofluorescence, were used to correlate depression-like behaviors with underlying molecular and physiological events.

RESULTS

Overexpression of FXR, whose levels were upregulated by CUS in hippocampal CA1, induced or aggravated depression-like behaviors in stress-naïve and CUS-exposed mice, while FXR short hairpin RNA (shRNA) ameliorated such symptoms in CUS-exposed mice. The behavioral effects of FXR were found to be associated with changes in CREB-brain-derived neurotrophic factor (BDNF) signaling, as FXR overexpression aggravated CUS-induced reduction in BDNF levels while the use of FXR shRNA or disruption of FXR-CREB signaling reversed the CUS-induced reduction in the phosphorylated CREB and BDNF levels. Molecular analysis revealed that FXR shRNA prevented CUS-induced cytoplasmic translocation of CREB-regulated transcription coactivator 2 (CRTC2); CRTC2 overexpression and CRTC2 shRNA abrogated the regulatory effect of FXR overexpression or FXR shRNA on CUS-induced depression-like behaviors.

CONCLUSIONS

In stress conditions, increased FXR in the CA1 inhibits CREB by targeting CREB and driving the cytoplasmic translocation of CRTC2. Uncoupling of the FXR-CREB complex may be a novel strategy for depression treatment.

Transcriptomic predictors of inflammation-induced depressed mood

Inflammation plays a significant role in the pathophysiology of depression. However, not all individuals exposed to inflammatory challenge develop depression, and identifying those at risk is necessary to develop targeted monitoring, prevention, and treatment strategies. Within a randomized double-blind placebo-controlled study (n = 115), we examined whether leukocyte transcriptome profiles predicted inflammation-induced depressed mood in volunteers who received low-dose intravenous endotoxin (n = 58; aged 18-50). At baseline, transcription factor (TF) activities were assessed using genome-wide transcriptional profiling of peripheral blood mononuclear cells and promoter-based bioinformatic analyses. Then, participants were administered endotoxin. Self-reported depressed mood was assessed using the Profile of Mood States. Based on extant studies linking transcriptional profiles to depressive disorder, we examined whether post-endotoxin depressed mood is predicted by baseline activity of TFs related to immune activation, sympathetic activation, and glucocorticoid insensitivity: respectively, nuclear factor kappa B (NF-kB), cAMP response element-binding protein (CREB), and glucocorticoid receptor (GR). Twenty-one participants (36%) experienced an increase in depressed mood from baseline to 2 h post endotoxin, when depressive response peaks. Bioinformatics analyses controlling for age, sex, ethnicity, body mass index, and physical sickness response revealed that post-endotoxin depressed mood was predicted by increased baseline activity of TFs related to inflammation (NF-kB) and beta-adrenergic signaling (CREB) and by decreased activity of GR-related TFs (P's < 0.001). Inflammation-induced depressed mood is predicted by peripheral transcriptome profiles related to immune activation, sympathetic activation, and glucocorticoid insensitivity. With further replication, these stress-related molecular profiles could be used for a novel genomic approach for identifying individuals at high-risk for the inflammatory subtype of depression.

Altered Expression of Phox2 Transcription Factors in the Locus Coeruleus in Major Depressive Disorder Mimicked by Chronic Stress and Corticosterone Treatment In Vivo and In Vitro

Phox2a and Phox2b are two homeodomain transcription factors playing a pivotal role in the development of noradrenergic neurons during the embryonic period. However, their expression and function in adulthood remain to be elucidated. Using human postmortem brain tissues, rat stress models and cultured cells, this study aimed to examine the alteration of Phox2a and Phox2b expression. The results show that Phox2a and Phox2b are normally expressed in the human locus coeruleus (LC) in adulthood. Furthermore, the levels of Phox2a protein and mRNA and protein levels of Phox2b were significantly elevated in the LC of brain donors that suffered from the major depressive disorder, as compared to age-matched and psychiatrically normal control donors. Fischer 344 rats subjected to chronic social defeat showed higher mRNA and protein levels of Phox2a and Phox2b in the LC, as compared to non-stressed control rats. In rats chronically administered oral corticosterone, mRNA and protein levels of Phox2b, but not Phox2a, in the LC were significantly increased. In addition, the corticosterone-induced increase in Phox2b protein was reversed by simultaneous treatment with either mifepristone or spironolactone. Exposing SH-SY5Y cells to corticosterone significantly increased expression of Phox2a and Phox2b, which was blocked by corticosteroid receptor antagonists. Taken together, these experiments reveal that Phox2 genes are expressed throughout the lifetime in the LC of humans and Fischer 344 rats. Alterations in their expression may play a role in major depressive disorder and possibly other stress-related disorders through their modulatory effects on the noradrenergic phenotype.

Association analysis in over 329,000 individuals identifies 116 independent variants influencing neuroticism

Neuroticism is a relatively stable personality trait characterized by negative emotionality (for example, worry and guilt) 1 ; heritability estimated from twin studies ranges from 30 to 50% 2 , and SNP-based heritability ranges from 6 to 15% 3-6 . Increased neuroticism is associated with poorer mental and physical health 7,8 , translating to high economic burden 9 . Genome-wide association studies (GWAS) of neuroticism have identified up to 11 associated genetic loci 3,4 . Here we report 116 significant independent loci from a GWAS of neuroticism in 329,821 UK Biobank participants; 15 of these loci replicated at P < 0.00045 in an unrelated cohort (N = 122,867). Genetic signals were enriched in neuronal genesis and differentiation pathways, and substantial genetic correlations were found between neuroticism and depressive symptoms (r g = 0.82, standard error (s.e.) = 0.03), major depressive disorder (MDD; r g = 0.69, s.e. = 0.07) and subjective well-being (r g = -0.68, s.e. = 0.03) alongside other mental health traits. These discoveries significantly advance understanding of neuroticism and its association with MDD.

Alterations in leukocyte transcriptional control pathway activity associated with major depressive disorder and antidepressant treatment

Major depressive disorder (MDD) is associated with a significantly elevated risk of developing serious medical illnesses such as cardiovascular disease, immune impairments, infection, dementia and premature death. Previous work has demonstrated immune dysregulation in subjects with MDD. Using genome-wide transcriptional profiling and promoter-based bioinformatic strategies, we assessed leukocyte transcription factor (TF) activity in leukocytes from 20 unmedicated MDD subjects versus 20 age-, sex- and ethnicity-matched healthy controls, before initiation of antidepressant therapy, and in 17 of the MDD subjects after 8 weeks of sertraline treatment. In leukocytes from unmedicated MDD subjects, bioinformatic analysis of transcription control pathway activity indicated an increased transcriptional activity of cAMP response element-binding/activating TF (CREB/ATF) and increased activity of TFs associated with cellular responses to oxidative stress (nuclear factor erythroid-derived 2-like 2, NFE2l2 or NRF2). Eight weeks of antidepressant therapy was associated with significant reductions in Hamilton Depression Rating Scale scores and reduced activity of NRF2, but not in CREB/ATF activity. Several other transcriptional regulation pathways, including the glucocorticoid receptor (GR), nuclear factor kappa-B cells (NF-κB), early growth response proteins 1-4 (EGR1-4) and interferon-responsive TFs, showed either no significant differences as a function of disease or treatment, or activities that were opposite to those previously hypothesized to be involved in the etiology of MDD or effective treatment. Our results suggest that CREB/ATF and NRF2 signaling may contribute to MDD by activating immune cell transcriptome dynamics that ultimately influence central nervous system (CNS) motivational and affective processes via circulating mediators.

Treadmill exercise alleviates stress-induced impairment of social interaction through 5-hydroxytryptamine 1A receptor activation in rats

Brain-derived neurotrophic factor (BDNF) and its receptors tyrosine kinase B (trkB), and cyclic adenosine monophosphate response element binding protein (CREB) have been suggested as the neurobiological risk factors causing depressive disorder. Serotonin (5-hydroxytryptamine, 5-HT) plays an important role in the pathogenesis of depression. We in-vestigated the effect of treadmill exercise on social interaction in relation with BDNF and 5-HT expressions following stress in rats. Stress was induced by applying inescapable 0.2 mA electric foot shock to the rats for 7 days. The rats in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 4 weeks. Social interaction test and western blot for BDNF, TrkB, pCREB, and 5-HT1A in the hippocampus were performed. The results indicate that the spend time with unfamiliar partner was decreased by stress, in contrast, treadmill exercise increased the spending time in the stress-induced rats. Expressions of BDNF, TrkB, and pCREB were decreased by stress, in contrast, treadmill exercise enhanced expressions of BDNF, TrkB, and pCREB in the stress-induced rats. In addition, 5-HT1A receptor expression was de-creased by stress, in contrast, treadmill exercise enhanced 5-HT1A expression in the stress-induced rats. In the present study, treadmill exercise alleviated stress-induced social interaction impairment through enhancing hippocampal plasticity and serotonergic function in the hippocampus. These effects of treadmill exercise are achieved through 5-HT1A receptor activation.

Effects of desipramine treatment on stress-induced up-regulation of norepinephrine transporter expression in rat brains

RATIONALE

Many studies demonstrate down-regulation of the norepinephrine transporter (NET) by desipramine (DMI) in vitro and in stress-naive rats. Little is known regarding regulation of the NET in stressed animals.

OBJECTIVE

The present study was designed to investigate effects of DMI on the expression of NET and protein kinases in the stress rat.

METHODS

Adult Fischer 344 rats were subjected to chronic social defeat (CSD) for 4 weeks. DMI (10 mg/kg, intraperitoneal (i.p.)) was administered concurrently with CSD or 1 or 2 weeks after cessation of CSD. Sucrose consumption, NET expression, and protein kinases were measured.

RESULTS

CSD significantly increased messenger RNA (mRNA) and protein levels of NET in the locus coeruleus, as well as NET protein levels in the hippocampus, frontal cortex, and amygdala. These effects were nearly abolished when DMI was administered concurrently with CSD. CSD-induced up-regulation of NET expression in the locus coeruleus, hippocampus, and amygdala lasted at least 2 weeks after cessation of CSD, an effect that was significantly attenuated by 1 or 2 weeks of DMI treatment starting from cessation of the CSD. Concurrent administration of DMI with CSD did not markedly interfere with CSD-induced decreases in protein levels of protein kinases A and C in these brain regions, but it did reverse the CSD-induced reduction in phosphorylated cAMP response element-binding (pCREB) protein levels in most brain regions.

CONCLUSION

These findings suggest that NET regulation by DMI occurs in both stressed and behaviorally naive rats, and DMI-induced changes in pCREB may be involved.

Chronic unpredictable stress (CUS)-induced anxiety and related mood disorders in a zebrafish model: altered brain proteome profile implicates mitochondrial dysfunction

Anxiety and depression are major chronic mood disorders, and the etiopathology for each appears to be repeated exposure to diverse unpredictable stress factors. Most of the studies on anxiety and related mood disorders are performed in rodents, and a good model is chronic unpredictable stress (CUS). In this study, we have attempted to understand the molecular basis of the neuroglial and behavioral changes underlying CUS-induced mood disorders in the simplest vertebrate model, the zebrafish, Danio rerio. Zebrafish were subjected to a CUS paradigm in which two different stressors were used daily for 15 days, and thorough behavioral analyses were performed to assess anxiety and related mood disorder phenotypes using the novel tank test, shoal cohesion and scototaxis. Fifteen days of exposure to chronic stressors appears to induce an anxiety and related mood disorder phenotype. Decreased neurogenesis, another hallmark of anxiety and related disorders in rodents, was also observed in this zebrafish model. The common molecular markers of rodent anxiety and related disorders, corticotropin-releasing factor (CRF), calcineurin (ppp3r1a) and phospho cyclic AMP response element binding protein (pCREB), were also replicated in the fish model. Finally, using 2DE FTMS/ITMSMS proteomics analyses, 18 proteins were found to be deregulated in zebrafish anxiety and related disorders. The most affected process was mitochondrial function, 4 of the 18 differentially regulated proteins were mitochondrial proteins: PHB2, SLC25A5, VDAC3 and IDH2, as reported in rodent and clinical samples. Thus, the zebrafish CUS model and proteomics can facilitate not only uncovering new molecular targets of anxiety and related mood disorders but also the routine screening of compounds for drug development.

Downregulation of serotonergic gene expression in the Raphe nuclei of the midbrain under chronic social defeat stress in male mice

There is ample experimental evidence supporting the hypothesis that the brain serotonergic system is involved in the control of chronic social defeat stress (CSDS), depression, and anxiety. The study aimed to analyze mRNA levels of the serotonergic genes in the raphe nuclei of midbrain that may be associated with chronic social defeats consistently shown by male mice in special experimental settings. The serotonergic genes were the Tph2, Sert, Maoa, and Htr1a. The Bdnf and Creb genes were also studied. The experimental groups were composed of male mice with experience of defeats in 21 daily encounters and male mice with the same track record of defeats followed by a no-defeat period without agonistic interactions (relative rest for 14 days). It has been shown that mRNA levels of the Tph2, Maoa, Sert, Htr1a, Bdnf, and Creb genes in the raphe nuclei of defeated mice are decreased as compared with the controls. The expression of the serotonergic genes as well as the Creb gene is not restored to the control level after the 2 weeks of relative rest. mRNA levels of Bdnf gene are not recovered to the control levels, although some upregulation was observed in rested losers. CSDS experience inducing the development of mixed anxiety/depression-like state in male mice downregulates the expression of serotonergic genes associated with the synthesis, inactivation, and reception of serotonin. The Bdnf and Creb genes in the midbrain raphe nuclei are also downregulated under CSDS. Period of relative rest is not enough for most serotonergic genes to recover expression to the control levels.

European Group for the Study of Resistant Depression (GSRD)--where have we gone so far: review of clinical and genetic findings

The primary objective of this review is to give an overview of the main findings of the European multicenter project "Patterns of Treatment Resistance and Switching Strategies in Affective Disorder", performed by the Group for the Study of Resistant Depression (GSRD). The aim was to study methodological issues, operational criteria, clinical characteristics, and genetic variables associated with treatment resistant depression (TRD), that is failure to reach response after at least two consecutive adequate antidepressant trials. The primary findings of clinical variables associated with treatment resistance include comorbid anxiety disorders as well as non-response to the first antidepressant received lifetime. Although there is a plethora of hints in textbooks that switching the mechanism of action should be obtained in case of nonresponse to one medication, the results of the GSRD challenge this notion by demonstrating in retrospective and prospective evaluations that staying on the same antidepressant mechanism of action for a longer time is more beneficial than switching, however, when switching is an option there is no benefit to switch across class. The GSRD candidate gene studies found that metabolism status according to cytochrome P450 gene polymorphisms may not be helpful to predict response and remission rates to antidepressants. Significant associations with MDD and antidepressant treatment response were found for COMT SNPs. Investigating the impact of COMT on suicidal behaviour, we found a significant association with suicide risk in MDD patients not responding to antidepressant treatment, but not in responders. Further significant associations with treatment response phenotypes were found with BDNF, 5HTR2A and CREB1. Additional investigated candidate genes were DTNBP1, 5HT1A, PTGS2, GRIK4 and GNB3.

Chronic social defeat up-regulates expression of norepinephrine transporter in rat brains

Stress has been reported to activate the locus coeruleus (LC)-noradrenergic system. However, the molecular link between chronic stress and noradrenergic neurons remains to be elucidated. In the present study adult Fischer 344 rats were subjected to a regimen of chronic social defeat (CSD) for 4weeks. Measurements by in situ hybridization and Western blotting showed that CSD significantly increased mRNA and protein levels of the norepinephrine transporter (NET) in the LC region and NET protein levels in the hippocampus, frontal cortex and amygdala. CSD-induced increases in NET expression were abolished by adrenalectomy or treatment with corticosteroid receptor antagonists, suggesting the involvement of corticosterone and corticosteroid receptors in this upregulation. Furthermore, protein levels of protein kinase A (PKA), protein kinase C (PKC), and phosphorylated cAMP-response element binding (pCREB) protein were significantly reduced in the LC and its terminal regions by the CSD paradigm. Similarly, these reduced protein levels caused by CSD were prevented by adrenalectomy. However, effects of corticosteroid receptor antagonists on CSD-induced down-regulation of PKA, PKC, and pCREB proteins were not consistent. While mifeprestone and spironolactone, either alone or in combination, totally abrogate CSD effects on these protein levels of PKA, PKC and pCREB in the LC and those in the hippocampus, frontal cortex and amygdala, their effects on PKA and PKC in the hippocampus, frontal cortex and amygdala were region-dependent. The present findings indicate a correlation between chronic stress and activation of the noradrenergic system. This correlation and CSD-induced alteration in signal transduction molecules may account for their critical effects on the development of symptoms of major depression.

Pharmacogenetics of antidepressants

Up to 60% of depressed patients do not respond completely to antidepressants (ADs) and up to 30% do not respond at all. Genetic factors contribute for about 50% of the AD response. During the recent years the possible influence of a set of candidate genes as genetic predictors of AD response efficacy was investigated by us and others. They include the cytochrome P450 superfamily, the P-glycoprotein (ABCB1), the tryptophan hydroxylase, the catechol-O-methyltransferase, the monoamine oxidase A, the serotonin transporter (5-HTTLPR), the norepinephrine transporter, the dopamine transporter, variants in the 5-hydroxytryptamine receptors (5-HT1A, 5-HT2A, 5-HT3A, 5-HT3B, and 5-HT6), adrenoreceptor beta-1 and alpha-2, the dopamine receptors (D2), the G protein beta 3 subunit, the corticotropin releasing hormone receptors (CRHR1 and CRHR2), the glucocorticoid receptors, the c-AMP response-element binding, and the brain-derived neurotrophic factor. Marginal associations were reported for angiotensin I converting enzyme, circadian locomotor output cycles kaput protein, glutamatergic system, nitric oxide synthase, and interleukin 1-beta gene. In conclusion, gene variants seem to influence human behavior, liability to disorders and treatment response. Nonetheless, gene × environment interactions have been hypothesized to modulate several of these effects.

Signal transduction pathways in the pathophysiology of bipolar disorder

Signal transduction pathways and genes associated with cellular life and death have received much attention in bipolar disorder (BPD) and provide scientists with molecular targets for understanding the biological basis of BPD. In this chapter, we describe the signal transduction pathways involved in the molecular biology of BPD and the indications for the mechanisms of disease and treatment. We discuss the BPD literature with respect to the disease itself and the effects of mood stabilizer treatment on cellular receptors, including G-protein-coupled receptors, glutamate receptors, and tyrosine receptor kinase. We also discuss the intracellular alterations observed in BPD to second messenger systems, such as cyclic adenosine monophosphate (cAMP), protein kinase A, phosphoinositide pathways, glycogen synthase kinase-3, protein kinase B, Wnt, and arachidonic acid. We describe how receptor activation and modulation of second messengers occurs, and how transcription factors are activated and altered in this disease (e.g., the transcription factors ?-catenin, cAMP response element binding protein, heat shock transcription factor-1, and activator protein-1). Abnormalities in intracellular signal transduction pathways could generate a functional discrepancy in numerous neurotransmitter systems, which may explain the varied clinical symptoms observed in BPD. The influence of mood stabilizers on transcription factors may be important in connecting the regulation of gene expression to neuroplasticity and cellular resilience.

Epistatic interaction of CREB1 and KCNJ6 on rumination and negative emotionality

G protein-activated K+ channel 2 (GIRK2) and cAMP-response element binding protein (CREB1) are involved in synaptic plasticity and their genes have been implicated depression and memory processing. Excessive rumination is a core cognitive feature of depression which is also present in remission. High scores on the Ruminative Response Scale (RRS) questionnaire are predictive of relapse and recurrence. Since rumination involves memory, we tested the hypothesis that variation in the genes encoding GIRK2 (KCNJ6) and CREB1 mechanisms would influence RRS scores. GIRK2 and CREB1 polymorphisms were studied in two independent samples (n=651 and n=1174) from the general population. Strongly significant interaction between the TT genotype of rs2070995 (located in KCNJ6) and the GG genotype of rs2253206 (located in CREB1) on RRS were found in both samples. These results were validated in an independent third sample (n=565; individuals with personality disorders) showing significant main effect of the variants mentioned as well as significant interaction on a categorical diagnosis of Cluster C personality disorder (obsessional-compulsive, avoidant and dependent) in which rumination is a prominent feature. Our results suggest that genetic epistasis in post-receptor signaling pathways in memory systems may have relevance for depression and its treatment.

Comparative analysis of acute and chronic corticosteroid pharmacogenomic effects in rat liver: transcriptional dynamics and regulatory structures

Background

Comprehensively understanding corticosteroid pharmacogenomic effects is an essential step towards an insight into the underlying molecular mechanisms for both beneficial and detrimental clinical effects. Nevertheless, even in a single tissue different methods of corticosteroid administration can induce different patterns of expression and regulatory control structures. Therefore, rich in vivo datasets of pharmacological time-series with two dosing regimens sampled from rat liver are examined for temporal patterns of changes in gene expression and their regulatory commonalities.

Results

The study addresses two issues, including (1) identifying significant transcriptional modules coupled with dynamic expression patterns and (2) predicting relevant common transcriptional controls to better understand the underlying mechanisms of corticosteroid adverse effects. Following the orientation of meta-analysis, an extended computational approach that explores the concept of agreement matrix from consensus clustering has been proposed with the aims of identifying gene clusters that share common expression patterns across multiple dosing regimens as well as handling challenges in the analysis of microarray data from heterogeneous sources, e.g. different platforms and time-grids in this study. Six significant transcriptional modules coupled with typical patterns of expression have been identified. Functional analysis reveals that virtually all enriched functions (gene ontologies, pathways) in these modules are shown to be related to metabolic processes, implying the importance of these modules in adverse effects under the administration of corticosteroids. Relevant putative transcriptional regulators (e.g. RXRF, FKHD, SP1F) are also predicted to provide another source of information towards better understanding the complexities of expression patterns and the underlying regulatory mechanisms of those modules.

Conclusions

We have proposed a framework to identify significant coexpressed clusters of genes across multiple conditions experimented from different microarray platforms, time-grids, and also tissues if applicable. Analysis on rich in vivo datasets of corticosteroid time-series yielded significant insights into the pharmacogenomic effects of corticosteroids, especially the relevance to metabolic side-effects. This has been illustrated through enriched metabolic functions in those transcriptional modules and the presence of GRE binding motifs in those enriched pathways, providing significant modules for further analysis on pharmacogenomic corticosteroid effects.

Hyperforin is a modulator of inducible nitric oxide synthase and phagocytosis in microglia and macrophages

Upon activation, microglia, the immunocompetent cells in the brain, get highly phagocytic and release pro-inflammatory mediators like nitric oxide (NO). Excessive NO production is pivotal in neurodegenerative disorders, and there is evidence that abnormalities in NO production and inflammatory responses may at least support a range of neuropsychiatric disorders, including depression. Although extracts of St. John's wort (Hypericum perforatum L.) have been used for centuries in traditional medicine, notably for the treatment of depression, there is still considerable lack in scientific knowledge about the impact on microglia. We used N11 and BV2 mouse microglia, as well as RAW 264.7 macrophages to investigate the effects of St. John's wort extract and constituents thereof on NO production Moreover, flow cytometry and fluorescence microscopy were employed to analyze the influence on phagocytosis, transcription factor activation states, and cell motility. We found that extracts of St. John's wort efficiently suppress lipopolysaccharide-induced NO release and identified hyperforin as the responsible compound, being effective at concentrations between 0.25 and 0.75 microM. The reduced NO production was mediated by diminished inducible nitric oxide synthase expression on the mRNA and protein level. In addition, at similar concentrations, hyperforin reduced zymosan phygocytosis to 20-40% and putatively acted by downregulating the CD206 macrophage mannose receptor and modulation of cell motility. We found that the observed effects correlate with a suppression of the activated state of Nf-kappaB and phospho-CREB, while c-JUN, STAT1, and HIF-1alpha activity and cyclooxygenase-2 expression remained unaffected by hyperforin. These results reveal that hyperforin influences pro-inflammatory and immunological responses of microglia that are involved in the progression of neuropathologic disorders.

Suicide neurobiology

In this review, we examine the history of the neurobiology of suicide, as well as the genetics, molecular and neurochemical findings in suicide research. Our analysis begins with a summary of family, twin, and adoption studies, which provide support for the investigation of genetic variation in suicide risk. This leads to an overview of neurochemical findings restricted to neurotransmitters and their receptors, including recent findings in whole genome gene expression studies. Next, we look at recent studies investigating lipid metabolism, cell signalling with a particular emphasis on growth factors, stress systems with a focus on the role of polyamines, and finally, glial cell pathology in suicide. We conclude with a description of new ideas to study the neurobiology of suicide, including subject-specific analysis, protein modification assessment, neuroarchitecture studies, and study design strategies to investigate the complex suicide phenotype.

Phosphorylation status of glucocorticoid receptor, heat shock protein 70, cytochrome c and Bax in lymphocytes of euthymic, depressed and manic bipolar patients

Bipolar disorder (BD), a severe mental illness, has been correlated with alterations in glucocorticoid receptor (GR) signaling. Since it is phosphorylated GR that contributes to receptor function and determines its transcriptional activity, the Ser211 being a biomarker for activated GR in vivo, it is pertinent that we seek to determine the putative role of the total phosphorylation status of GR and site-specific phosphorylation at serine 211 (S211) in BD and their possible association with parameters of apoptosis. In lymphocytes from 48 BD patients under multiple psychotropic therapy and 20 healthy subjects, we measured whole cell GR, total GR phosphorylation, and phosphorylation of GR at serine 211 in nucleus, using immunoprecipitation, phosphospecific antibody and Western-blot analysis. Cytosolic cytochrome c and Bax and whole cell HSP70 were determined by immunoblot analysis. One-way ANOVA statistical analysis was carried out. Total phosphorylated GR was lower (P<0.001) while the GR S211 was higher (P<0.001) in all BD patients as compared to healthy subjects. HSP70 was reduced in euthymic (P<0.05), depressed (P<0.001) and manic (P<0.001) as compared to healthy subjects. Cytochrome c was higher in all-patient groups as compared to healthy subjects, however without reaching statistical significance (P>0.05). Bax levels were lower in the cytosolic fraction of all three BD groups. We provide the first evidence of altered GR phosphorylation joined with signs of apoptosis in lymphocytes of BD patients and suggest that the phosphorylation status of GR may play a role in the pathophysiology of bipolar disorder.

Lithium response and genetic variation in the CREB family of genes

Bipolar disorder (BD) is a severe psychiatric disorder that affects 1% of the population. Recently, there have been many attempts to identify specific genes that are involved in BD; however, the task of finding susceptibility genes is not easy due to the complexity of the disorder. Since lithium (Li) has been used for over 40 years now as an effective prophylactic agent and response to Li treatment seems to be, at least in part, genetically determined, classification according to Li response is a manner through which more homogeneous populations can be obtained for investigation. It has previously been suggested that Li exerts an effect on signal transduction pathways, such as the cyclic adenosine monophosphate (cAMP) pathway. We carried out an association study of BD with CREB1, CREB2 and CREB3 genes, located at ch 2q32.3-q34, 22q13.1 and 9pter-p22.1, respectively. A total of three promoter single nucleotide polymorphisms (SNP), 14 SNPs in the UTR, 6 exonic and 15 intronic SNPs were investigated for their frequency and haplotype distribution in a BD sample of 180 lithium responders and 69 nonresponders and 127 controls using a SNaPshot multiplex reaction from Applied Biosystems, a modified fluorescent single base pair extension procedure. Following correction for multiple testing, our results suggest that the CREB1-1H SNP (G/A change, P < 0.002) and the CREB1-7H SNP (T/C change, P < 0.002) may be associated with BD and/or lithium response.

Adenylyl cyclase-cyclicAMP signaling in mood disorders: role of the crucial phosphorylating enzyme protein kinase A

Mood disorders are among the most prevalent and recurrent forms of psychiatric illnesses. In the last decade, there has been increased understanding of the biological basis of mood disorders. In fact, novel mechanistic concepts of the neurobiology of unipolar and bipolar disorders are evolving based on recent pre-clinical and clinical studies, most of which now focus on the role of signal transduction mechanisms in these psychiatric illnesses. Particular investigative emphasis has been given to the role of phosphorylating enzymes, which are crucial in regulating gene expression and neuronal and synaptic plasticity. Among the most important phosphorylating enzyme is protein kinase A (PKA), a component of adenylyl cyclase-cyclic adenosine monophosphate (AC-cAMP) signaling system. In this review, we critically and comprehensively discuss the role of various components of AC-cAMP signaling in mood disorders, with a special focus on PKA, because of the interesting observation that have been made about its involvement in unipolar and bipolar disorders. We also discuss the functional significance of the findings regarding PKA by discussing the role of important PKA substrates, namely, Rap-1, cyclicAMP-response element binding protein, and brain-derived neurotrophic factor. These studies suggest the interesting possibility that PKA and related signaling molecules may serve as important neurobiological factors in mood disorders and may be relevant in target-specific therapeutic interventions for these disorders.

CREB-regulated diurnal activity patterns are not indicative for depression-like symptoms in mice and men

Activation of the transcription factor CREB by Ser142 phosphorylation is implicated in synchronizing circadian rhythmicity, which is disturbed in many depressive patients. Hence, one could assume that emotional behaviour and neuroendocrinological markers would be altered in CREB(S142A) mice, in which serine 142 is replaced by alanine, preventing phosphorylation at this residue. Moreover, associations of CREB Ser142 and seasonal affective disorder (SAD) might be detectable by the analysis of single-nucleotide polymorphisms (SNPs) in the CREB gene close to the Ser142 residue in SAD patients. However, neither CREB(S142A) mice demonstrate features of depression, nor there is evidence for an association of SAD with the CREB genotypes. Nevertheless, in humans there is an association of a global seasonality score and circadian rhythmicity with the CREB genotypes in healthy control probands, but not SAD patients. This parallels the phenotype of CREB(S142A) mice, presenting alterations of circadian rhythm and light-induced entrainment. Thus it is reasonable to assume that CREB Ser142 represents a molecular switch in mice and men, which is responsible for the (dys)regulation of circadian rhythms.

Effects of low-level formaldehyde exposure on synaptic plasticity-related gene expression in the hippocampus of immunized mice

We examined the effects of inhalative exposure to formaldehyde (FA, 400 ppb) on N-methyl-D-aspartate (NMDA) receptor subunits (NR2A and NR2B), dopamine receptor subtypes (D1 and D2), cyclic AMP responsive element-binding protein (CREB)-1, CREB-2, FosB/DeltaFosB, and transient receptor potential vanilloid receptor (TRPV1) in the hippocampus of ovalbumin-immunized mice using quantitative real-time PCR. Western blot analyses for pCREB were performed. The mRNA levels of NR2A, D1 and D2 receptors, and CREB-1 were significantly increased by FA, but NR2B, CREB-2, FosB/DeltaFosB, and TRPV1 mRNA levels remained unchanged. Treatment with MK-801 normalized the mRNA levels induced by FA. There was no significant effect of FA exposure and MK-801 treatment on the protein level of pCREB. These results indicate that FA exposure selectively up-regulates hippocampal gene expression in immunologically sensitized mice. The FA effects are presumably mediated by glutamatergic neurotransmission through NMDA receptors.

A20 attenuates vascular smooth muscle cell proliferation and migration through blocking PI3k/Akt singling in vitro and in vivo

A20 was originally characterized as a TNF-inducible gene in human umbilical vein endothelial cells. It is also induced in many other cell types by a wide range of stimuli. Expression of A20 has been shown to protect from TNF-induced apoptosis and also functions via a negative-feedback loop to block NF-kappaB activation induced by TNF and other stimuli. However, there are no reports on whether A20 can inhibit vascular smooth muscle cell proliferation in vivo. Here, we examined the effects of A20 on neointimal formation after balloon injury and TNF-alpha-induced vascular smooth muscle cells (VSMCs) proliferation and migration, as well as related molecular mechanisms in vitro and in vivo. We introduced adenovirus expressing A20 or GFP into rat carotid arterial segments after balloon injury. The effects of A20 were evaluated 14 days after gene delivery with morphometry and immunohistochemical staining for proliferating and apoptotic cells. Ad-A20 infection resulted in a significantly lower intima to media ratio and a greater lumen area compared with Ad-GFP infected group. Proliferation index was significantly reduced 14 days in Ad-A20 infection group. However, apoptotic index and caspase-3 activity were not significantly different between any groups at 14 days. In vitro experiments were performed to show that A20 markedly inhibited TNF-alpha-induced proliferation and migration in VSMCs. Further studies showed that A20 expression blocked artery injury- and TNF-alpha-activated PI3K/Akt/GSK3beta/CREB pathway in vivo and in vitro. In conclusion, A20 attenuates neointimal formation after arterial injury as well as cell proliferation and migration in response to TNF-alpha in VSMCs through blocking PI3K/Akt/GSKbeta-dependent activation of CREB.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Proposed multigenic Composite Inheritance in major depression

Various rationale have been considered in the familial inheritance pattern of major depression ranging from simple one-gene Mendelian inheritance to pseudo-additive gene action. We instead predict broad genetic expressivity patterns in the progeny of parents where at least one parent has recurrent major depression. In keeping with this idea, we feel that recurrent major depression could involve an expression imbalance of "normal" genes either exclusively or along with allelic variation(s). The patterns of pathology are theoretically conceptualized as qualitative and quantitative, meaning that expressivity of the genetic pattern in these children may range from minimal to complete even among siblings. Thus, prediction of the particular genetic pattern expressed by a particular child might prove difficult. The complex inheritance pattern that we propose is referred to as Composite Inheritance. Composite Inheritance considers that both the up- and down-regulation of luxury genes and housekeeping genes are involved in this dichotomous qualitative inheritance pattern and also the wide quantitative expressivity. The luxury genes include such genes as those coding for the neurotransmitter transporters and receptors. The housekeeping genes found to date include those that code for proteins involved in gene transcription, secondary signaling systems, fatty acid metabolism and transport, and intracellular calcium homeostasis. Other luxury and housekeeping genes no doubt remain to be discovered. Our current research utilizes an empirical approach involving advanced genomics and specialized pattern recognition mathematics in families having at least one parent with recurrent major depression. The goal of our research is to develop a pattern recognition system of genetic expressivity in major depression to which prevention and early intervention may be tailored.

CRH, Stress, and Major Depression: A Psychobiological Interplay

Major depressive disorder (MDD) is a complex disease and is one of the leading causes of disability in our society. The provoking factors are multiple; acute and chronic psychological stress, severe early trauma experiences, somatic disease, and genetic factors all play a role. This review focuses on hyperdrive of corticotropin-releasing hormone (CRH) as the fundamental neurobiological correlate of MDD. CRH plays a key role in the adaptation to acute stress, but chronic CRH hyperdrive leads to a number of disadvantageous emotional and somatic effects. The evidence that the HPA axis is hyperactive in MDD, probably as a result of a primary hyperdrive of CRH, comes from multiple sources: biochemical studies, functional HPA axis tests, neuroimaging and postmortem studies, and clinical trials with HPA axis-related compounds. The liability to develop CRH hyperdrive is probably partly genetic. For a number of relevant genes, transgenic animal studies and human association studies indicate a role in HPA axis regulation and the liability to develop CRH hyperdrive. These data are reviewed. Finally, early adverse experience can produce a lasting effect on HPA axis regulation as well, probably leading to a lifelong tendency to develop chronic CRH hyperdrive in response to stress. This has been shown in a number of animal studies, and recently some data in humans with early trauma have become available as well. Taken together, these findings allow formulating an integrative hypothesis, with CRH hyperdrive at the core, bridging the old dichotomy between biology and psychology in our thinking about MDD.