The corticotropin-releasing hormone binding protein is associated with major depression in a population from Northern Sweden

Corticotropin Releasing Factor Binding Protein as a Novel Target to Restore Brain Homeostasis: Lessons Learned From Alcohol Use Disorder Research

Stress is well-known to contribute to the development of many psychiatric illnesses including alcohol and substance use disorder (AUD and SUD). The deleterious effects of stress have also been implicated in the acceleration of biological age, and age-related neurodegenerative disease. The physio-pathology of stress is regulated by the corticotropin-releasing factor (CRF) system, the upstream component of the hypothalamic-pituitary-adrenal (HPA) axis. Extensive literature has shown that dysregulation of the CRF neuroendocrine system contributes to escalation of alcohol consumption and, similarly, chronic alcohol consumption contributes to disruption of the stress system. The CRF system also represents the central switchboard for regulating homeostasis, and more recent studies have found that stress and aberrations in the CRF pathway are implicated in accelerated aging and age-related neurodegenerative disease. Corticotropin releasing factor binding protein (CRFBP) is a secreted glycoprotein distributed in peripheral tissues and in specific brain regions. It neutralizes the effects of CRF by sequestering free CRF, but may also possess excitatory function by interacting with CRF receptors. CRFBP’s dual role in influencing CRF bioavailability and CRF receptor signaling has been shown to have a major part in the HPA axis response. Therefore, CRFBP may represent a valuable target to treat stress-related illness, including: development of novel medications to treat AUD and restore homeostasis in the aging brain. This narrative review focuses on molecular mechanisms related to the role of CRFBP in the progression of addictive and psychiatric disorders, biological aging, and age-related neurodegenerative disease. We provide an overview of recent studies investigating modulation of this pathway as a potential therapeutic target for AUD and age-related neurodegenerative disease.

Increased protein and mRNA expression of corticotropin-releasing factor (CRF), decreased CRF receptors and CRF binding protein in specific postmortem brain areas of teenage suicide subjects

Overactivity of hypothalamic-pituitary-adrenal (HPA) axis function has been implicated in depression and suicidal behavior. This is based on the observation of an abnormal dexamethasone (DEX) and DEX-adrenocorticotropic hormone (ACTH) test in patients with depression and suicidal behavior. Recently, some studies have also found abnormalities of glucocorticoid receptors (GR), mineralocorticoid receptors (MR), corticotropin releasing factor (CRF), CRF receptors (CRF-R) and CRF binding protein (CRF-BP) in depressed and suicidal patients. Some investigators have also observed increased levels of CRF in the cerebrospinal fluid (CSF) and altered levels of MR, GR and CRF in the postmortem brain of depressed and suicidal subjects. We have earlier reported decreased protein and mRNA expression of GR and GILZ, a chaperone protein, in the postmortem brain of teenage suicide subjects. We have further studied CRF and its receptors in different areas of the postmortem brain of suicide subjects, i.e., the prefrontal cortex (PFC), hippocampus (HIPPO), subiculum and amygdala (AMY) from teenage suicide subjects. The CRF and its receptors were determined in the PFC (Brodmann area 9), HIPPO, subiculum and different amygdaloid nuclei from 24 normal control subjects and 24 teenage suicide subjects. Protein expression of CRF, its receptors and CRF-BP was determined by immunolabeling using the Western blot technique and mRNA expression was determined by real-time PCR (qPCR) technique. We found that the mRNA levels of CRF were significantly increased in the PFC, in the central amygdaloid nucleus (CeAMY) and in the subiculum. mRNA levels of CRF-R1 and CRF-BP were significantly decreased in the PFC. We did not find any changes in the HIPPO of any of the CRF components we studied. When we compared the protein expression of CRF components we found that CRF was significantly increased and CRF-R1, CRF-R2 and CRF-BP significantly decreased in the PFC. On the other hand, there were no changes in the protein expression of CRF components in the HIPPO. Our results in the postmortem brain suggest that, as found by clinical studies in the CSF, there are significant alterations of CRF and its receptors in the postmortem brain of teenage suicide subjects. These alterations of CRF and its components were region-specific, as changes were not generally observed in the HIPPO.

Importance of the brain corticosteroid receptor balance in metaplasticity, cognitive performance and neuro-inflammation

Bruce McEwen's discovery of receptors for corticosterone in the rat hippocampus introduced higher brain circuits in the neuroendocrinology of stress. Subsequently, these receptors were identified as mineralocorticoid receptors (MRs) that are involved in appraisal processes, choice of coping style, encoding and retrieval. The MR-mediated actions on cognition are complemented by slower actions via glucocorticoid receptors (GRs) on contextualization, rationalization and memory storage of the experience. These sequential phases in cognitive performance depend on synaptic metaplasticity that is regulated by coordinate MR- and GR activation. The receptor activation includes recruitment of coregulators and transcription factors as determinants of context-dependent specificity in steroid action; they can be modulated by genetic variation and (early) experience. Interestingly, inflammatory responses to damage seem to be governed by a similarly balanced MR:GR-mediated action as the initiating, terminating and priming mechanisms involved in stress-adaptation. We conclude with five questions challenging the MR:GR balance hypothesis.

Antidepressant Outcomes Predicted by Genetic Variation in Corticotropin-Releasing Hormone Binding Protein

OBJECTIVE

Genetic variation within the hypothalamic-pituitary-adrenal (HPA) axis has been linked to risk for depression and antidepressant response. However, these associations have yet to produce clinical gains that inform treatment decisions. The authors investigated whether variation within HPA axis genes predicts antidepressant outcomes within two large clinical trials.

METHOD

The test sample comprised 636 patients from the International Study to Predict Optimized Treatment in Depression (iSPOT-D) who completed baseline and 8-week follow-up visits and for whom complete genotyping data were available. The authors tested the relationship between genotype at 16 candidate HPA axis single-nucleotide polymorphisms (SNPs) and treatment outcomes for three commonly used antidepressants (escitalopram, sertraline, and extended-release venlafaxine), using multivariable linear and logistic regression with Bonferroni correction. Response and remission were defined using the Hamilton Depression Rating Scale. Findings were then validated using the Predictors of Remission in Depression to Individual and Combined Treatments (PReDICT) study of outcome predictors in treatment-naive patients with major depression.

RESULTS

The authors found that the rs28365143 variant within the corticotropin-releasing hormone binding protein (CRHBP) gene predicted antidepressant outcomes for remission, response, and symptom change. Patients homozygous for the G allele of rs28365143 had greater remission rates, response rates, and symptom reductions. These effects were specific to drug class. Patients homozygous for the G allele responded significantly better to the selective serotonin reuptake inhibitors escitalopram and sertraline than did A allele carriers. In contrast, rs28365143 genotype was not associated with treatment outcomes for the serotonin norepinephrine reuptake inhibitor venlafaxine. When patients were stratified by race, the overall effect of genotype on treatment response remained. In the validation sample, the GG genotype was again associated with favorable antidepressant outcomes, with comparable effect sizes.

CONCLUSIONS

These findings suggest that a specific CRHBP SNP, rs28365143, may have a role in predicting which patients will improve with antidepressants and which type of antidepressant may be most effective. The results add to the foundational knowledge needed to advance a precision approach to personalized antidepressant choices.

Corticotropin-releasing hormone-binding protein and stress: from invertebrates to humans

Corticotropin-releasing hormone (CRH) is a key regulator of the stress response. This peptide controls the hypothalamic-pituitary-adrenal (HPA) axis as well as a variety of behavioral and autonomic stress responses via the two CRH receptors, CRH-R1 and CRH-R2. The CRH system also includes an evolutionarily conserved CRH-binding protein (CRH-BP), a secreted glycoprotein that binds CRH with subnanomolar affinity to modulate CRH receptor activity. In this review, we discuss the current literature on CRH-BP and stress across multiple species, from insects to humans. We describe the regulation of CRH-BP in response to stress, as well as genetic mouse models that have been utilized to elucidate the in vivo role(s) of CRH-BP in modulating the stress response. Finally, the role of CRH-BP in the human stress response is examined, including single nucleotide polymorphisms in the human CRHBP gene that are associated with stress-related affective disorders and addiction. Lay summary The stress response is controlled by corticotropin-releasing hormone (CRH), acting via CRH receptors. However, the CRH system also includes a unique CRH-binding protein (CRH-BP) that binds CRH with an affinity greater than the CRH receptors. In this review, we discuss the role of this highly conserved CRH-BP in regulation of the CRH-mediated stress response from invertebrates to humans.

HPA Axis Interactions with Behavioral Systems

Perhaps the most salient behaviors that individuals engage in involve the avoidance of aversive experiences and the pursuit of pleasurable experiences. Engagement in these behaviors is regulated to a significant extent by an individual's hormonal milieu. For example, glucocorticoid hormones are produced by the hypothalamic-pituitary-adrenocortical (HPA) axis, and influence most aspects of behavior. In turn, many behaviors can influence HPA axis activity. These bidirectional interactions not only coordinate an individual's physiological and behavioral states to each other, but can also tune them to environmental conditions thereby optimizing survival. The present review details the influence of the HPA axis on many types of behavior, including appetitively-motivated behaviors (e.g., food intake and drug use), aversively-motivated behaviors (e.g., anxiety-related and depressive-like) and cognitive behaviors (e.g., learning and memory). Conversely, the manuscript also describes how engaging in various behaviors influences HPA axis activity. Our current understanding of the neuronal and/or hormonal mechanisms that underlie these interactions is also summarized. © 2016 American Physiological Society. Compr Physiol 6:1897-1934, 2016.

Teneurins, TCAP, and latrophilins: roles in the etiology of mood disorders

Mood disorders, including anxiety and depression, are thought to be characterized by disrupted neuronal synapses and altered brain plasticity. The etiology is complex, involving numerous regions of the brain, comprising a multitude of neurotransmitter and neuromodulator systems. Recently, new studies on the teneurins, an evolutionary ancient family of type II transmembrane proteins have been shown to interact with latrophilins (LPHN), a similarly phylogenetically old family of adhesion G protein-coupled receptors (GPCR) forming a transsynaptic adhesion and ligand-receptor pair. Each of the four teneurin proteins contains bioactive sequences termed the teneurin C-terminal associated peptides (TCAP-1-4), which possess a number of neuromodulatory effects. The primary structures of the TCAP are most closely similar to the corticotropin-releasing factor (CRF) family of peptides. CRF has been implicated in a number of diverse mood disorders. Via an association with dystroglycans, synthetic TCAP-1 administration to both embryonic and primary hippocampal cultures induces long-term changes in neuronal structure, specifically increased neurite outgrowth, dendritic branching, and axon growth. Rodent models treated with TCAP-1 show reduced anxiety responses in the elevated plus-maze, openfield test, and acoustic startle test and inhibited CRF-mediated cocaine-seeking behaviour. Thus the teneurin/TCAP-latrophilin interaction may play a major role in the origin, development and treatment of mood disorders.

Associations between Single-Nucleotide Polymorphisms in Corticotropin-Releasing Hormone-Related Genes and Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common functional disorder with distinct features of stress-related pathophysiology. A key mediator of the stress response is corticotropin-releasing hormone (CRH). Although some candidate genes have been identified in stress-related disorders, few studies have examined CRH-related gene polymorphisms. Therefore, we tested our hypothesis that single-nucleotide polymorphisms (SNPs) in CRH-related genes influence the features of IBS.

METHODS

In total, 253 individuals (123 men and 130 women) participated in this study. They comprised 111 IBS individuals and 142 healthy controls. The SNP genotypes in CRH (rs28364015 and rs6472258) and CRH-binding protein (CRH-BP) (rs10474485) were determined by direct sequencing and real-time polymerase chain reaction. The emotional states of the subjects were evaluated using the State-Trait Anxiety Inventory, Perceived Stress Scale, and the Self-rating Depression Scale.

RESULTS

Direct sequencing of the rs28364015 SNP of CRH revealed no genetic variation among the study subjects. There was no difference in the genotype distributions and allele frequencies of rs6472258 and rs10474485 between IBS individuals and controls. However, IBS subjects with diarrhea symptoms without the rs10474485 A allele showed a significantly higher emotional state score than carriers.

CONCLUSIONS

These results suggest that the CRH and CRH-BP genes have no direct effect on IBS status. However, the CRH-BP SNP rs10474485 has some effect on IBS-related emotional abnormalities and resistance to psychosocial stress.

Case-control study of glucocorticoid receptor and corticotrophin-releasing hormone receptor gene variants and risk of perinatal depression

Background

Depression during pregnancy or after childbirth is the most frequent perinatal illness affecting women of reproductive age. It could result in unfavourable outcomes for both women and their newborns. The incidence of perinatal depression is higher for those with family history of depression and other mental illness, suggesting the contribution of genetic factors. There is postulation that disruption or fluctuation of reproductive hormones could play a part in women who are sensitive to such changes.

Methods

This is a case-control study comparing the frequencies of candidate gene variants in patients with perinatal depression with controls. Patients of Chinese descent (N = 725) were recruited from the outpatient clinics of the hospital between 2010 and 2013. Controls were patients who came for postnatal consultations at the obstetrics clinics and scored ≤ 7 on the Edinburgh Postnatal Depression Scale (EPDS) at the postnatal screening programme of the hospital. Cases with confirmed diagnosis of clinical (major) depression related to pregnancy/postpartum were recruited from the hospital’s outpatient clinic. Genomic DNA was extracted from saliva samples and genotyped for the polymorphisms of interest. Differences between groups were assessed by chi-square analysis.

Results

CRHR1 rs242939 and rs1876828 were not polymorphic in the study population. There was no statistically significant association of perinatal depression for CRHR1 rs242941 and GR rs41423247 (BclI). When all subjects were grouped based on family history of mental illness, there was a statistically significant association of CRHR1 rs242941 with family history regardless of depression status (P = 0.043). There was also a statistically significant difference for GR rs41423247 and regularity of menstrual periods (P < 0.000). Although not statistically significant, women with perinatal depression showed a trend towards higher frequency of self-reported menstrual irregularity.

Conclusions

No evidence was found for the association of any of the genetic markers with perinatal depression in this study cohort. Instead, the possible genetic links were found in women with positive family history of mental illness and menstrual irregularity, suggesting these could be identifying risk markers for women.

Personalized Medicine and Mood Disorders

Some of the latest advances in personalized psychiatry with future research directions are discussed in this article. Many factors contribute to the phenotypic psychiatric profile in individual patients. These overlapping factors include but are not limited to genetics, epigenetics, central nervous system circuit alterations, family history, past personal history, environmental influences including early life stress, and more recent life stressors. The authors discuss the role of pharmacogenomics, particularly in the cytochrome P450 enzyme system in relation to treatment response. Despite some promising advances in personalized medicine in psychiatry, it is still in its early phases of development.

Drug addiction and stress-response genetic variability: association study in African Americans

Stress is a significant risk factor in the development of drug addictions and in addiction relapse susceptibility. This hypothesis-driven study was designed to determine if specific SNPs in genes related to stress response are associated with heroin and/or cocaine addiction in African Americans. The analysis included 27 genes (124 SNPs) and was performed independently for each addiction. The sample consisted of former heroin addicts in methadone maintenance treatment (n = 314), cocaine addicts (n = 281), and controls (n = 208). Fourteen SNPs showed nominally significant association with heroin addiction (p < 0.05), including the African-specific, missense SNP rs5376 (Asn334Ser) in the galanin receptor type 1 gene (GALR1) and the functional FKBP5 intronic SNP rs1360780. Thirteen SNPs showed association with cocaine addiction, including the synonymous SNPs rs237902, in the oxytocin receptor gene (OXTR), and rs5374 in GALR1. No signal remained significant after correction for multiple testing. Four additional SNPs (GALR1 rs2717162, AVP rs2282018, CRHBP rs1875999, and NR3C2 rs1040288) were associated with both addictions and may indicate common liability. The study provides preliminary evidence for novel association of variants in several stress-related genes with heroin and/or cocaine addictions and may enhance the understanding of the interaction between stress and addictions.

Personalized medicine in psychiatry: problems and promises

The central theme of personalized medicine is the premise that an individual's unique physiologic characteristics play a significant role in both disease vulnerability and in response to specific therapies. The major goals of personalized medicine are therefore to predict an individual's susceptibility to developing an illness, achieve accurate diagnosis, and optimize the most efficient and favorable response to treatment. The goal of achieving personalized medicine in psychiatry is a laudable one, because its attainment should be associated with a marked reduction in morbidity and mortality. In this review, we summarize an illustrative selection of studies that are laying the foundation towards personalizing medicine in major depressive disorder, bipolar disorder, and schizophrenia. In addition, we present emerging applications that are likely to advance personalized medicine in psychiatry, with an emphasis on novel biomarkers and neuroimaging.

Behavioral Studies and Genetic Alterations in Corticotropin-Releasing Hormone (CRH) Neurocircuitry: Insights into Human Psychiatric Disorders

To maintain well-being, all organisms require the ability to re-establish homeostasis in the presence of adverse physiological or psychological experiences. The regulation of the hypothalamic-pituitary adrenal (HPA) axis during stress is important in preventing maladaptive responses that may increase susceptibility to affective disorders. Corticotropin-releasing hormone (CRH) is a central stress hormone in the HPA axis pathway and has been implicated in stress-induced psychiatric disorders, reproductive and cardiac function, as well as energy metabolism. In the context of psychiatric disorders, CRH dysfunction is associated with the occurrence of post-traumatic stress disorder, major depression, anorexia nervosa, and anxiety disorders. Here, we review the synthesis, molecular signaling and regulation, as well as synaptic activity of CRH. We go on to summarize studies of altered CRH signaling in mutant animal models. This assembled data demonstrate an important role for CRH in neuroendocrine, autonomic, and behavioral correlates of adaptation and maladaptation. Next, we present findings regarding human genetic polymorphisms in CRH pathway genes that are associated with stress and psychiatric disorders. Finally, we discuss a role for regulators of CRH activity as potential sites for therapeutic intervention aimed at treating maladaptive behaviors associated with stress.

The kynurenine pathway in major depression: haplotype analysis of three related functional candidate genes

A consistent finding in major depressive disorder (MDD) research is dysfunction of the immune system. One of the relevant metabolic pathways in this regard is the kynurenine pathway. In patients with major depression, an imbalance between neuroprotective and neurotoxic arms of the pathway with lower plasma kynurenic acid concentration was demonstrated. Therefore, we investigated Single Nucleotide Polymorphism (SNP) and haplotype association of three candidate genes of the three enzymes involved in this metabolism. The three genes, namely, tryptophan hydroxylase 2 (TPH2), kynurenine 3 monooxygenase (KMO) and kynurenine amino transferase 3 (KAT III) SNPs and haplotype association analysis was performed in 338 (266 major depression and 72 bipolar depression) unrelated Caucasian patients with major depressive episodes and 310 age, gender and ethnicity matched controls. In sliding window analyses using PLINK of the haplotypes of KAT III, all windows which include the first SNP (rs12729558), the overall haplotype distribution (OMNIBUS) was significantly different between patients with a major depressive episode and control for all windows, with p-values ranging between 1.75 × 10=5 and 0.006. This is due to the haplotype CGCTCT (referring to 6 SNP window analysis), which is found in about 5.7% of patients and 1.9% of healthy controls. It was due to CGCTCT haplotype and the frequencies of this haplotype in both bipolar patients and patients with major depression showed significantly higher than the control population (p<0.001). This haplotype of KAT III gene CGCTCT may have effect on the function of this enzyme in formation of kynurenic acid in some patients with major depressive episodes.

Gene-environment interactions in geriatric depression

In older adults, several environmental challenges can potentially trigger the onset of an episode of major depression. Vulnerability to these challenges can be influenced by genetics. There is accumulating evidence for an interaction between stress and a serotonin transporter polymorphism, though there is also heterogeneity among studies. Other relevant genes include those encoding for the neuroendocrine stress axis, growth factors, and other monoaminergic systems. Each of these may interact with either predisposing traumas in early childhood or precipitating events later in life.

Poor replication of candidate genes for major depressive disorder using genome-wide association data

Data from the Genetic Association Information Network (GAIN) genome-wide association study (GWAS) in major depressive disorder (MDD) were used to explore previously reported candidate gene and single-nucleotide polymorphism (SNP) associations in MDD. A systematic literature search of candidate genes associated with MDD in case-control studies was performed before the results of the GAIN MDD study became available. Measured and imputed candidate SNPs and genes were tested in the GAIN MDD study encompassing 1738 cases and 1802 controls. Imputation was used to increase the number of SNPs from the GWAS and to improve coverage of SNPs in the candidate genes selected. Tests were carried out for individual SNPs and the entire gene using different statistical approaches, with permutation analysis as the final arbiter. In all, 78 papers reporting on 57 genes were identified, from which 92 SNPs could be mapped. In the GAIN MDD study, two SNPs were associated with MDD: C5orf20 (rs12520799; P=0.038; odds ratio (OR) AT=1.10, 95% CI 0.95-1.29; OR TT=1.21, 95% confidence interval (CI) 1.01-1.47) and NPY (rs16139; P=0.034; OR C allele=0.73, 95% CI 0.55-0.97), constituting a direct replication of previously identified SNPs. At the gene level, TNF (rs76917; OR T=1.35, 95% CI 1.13-1.63; P=0.0034) was identified as the only gene for which the association with MDD remained significant after correction for multiple testing. For SLC6A2 (norepinephrine transporter (NET)) significantly more SNPs (19 out of 100; P=0.039) than expected were associated while accounting for the linkage disequilibrium (LD) structure. Thus, we found support for involvement in MDD for only four genes. However, given the number of candidate SNPs and genes that were tested, even these significant may well be false positives. The poor replication may point to publication bias and false-positive findings in previous candidate gene studies, and may also be related to heterogeneity of the MDD phenotype as well as contextual genetic or environmental factors.

Associations between common arginine vasopressin 1b receptor and glucocorticoid receptor gene variants and HPA axis responses to psychosocial stress in a child psychiatric population

On the one hand, a suitable response to daily stressors is crucial for adequate functioning in any natural environment. On the other hand, depending on the individual's genetic makeup, prolonged stress that is accompanied by an inappropriate level of responsiveness may lead to physiological and psychiatric disorders. Several psychiatric conditions have been linked with stress and alterations in hypothalamic-pituitary-adrenal (HPA) activity. While stress is a general phenomenon, illness is only seen in a proportion of individuals, suggesting that genetic factors may play a role in the ability to cope with stress. In children, relatively little research has been conducted to determine the impact of genetic factors on the variability in HPA axis functioning. In the present exploratory investigation, 106 prepubertal children were studied to estimate the impact of four glucocorticoid receptor gene (NR3C1) polymorphisms (NR3C1-1 [rs10482605], ER22/23EK [rs6190], N363S [rs6195], N766N [rs6196]) and five arginine vasopressin (AVP) receptor 1b gene (AVPR1b) polymorphisms (AVPR1b_s1 [rs28536160], AVPR1b_s2 [rs28373064], AVPR1b_s3 [rs33976516], AVPR1b_s4 [rs33985287], AVPR1b_s5 [rs33933482]) on cortisol responses after a psychosocial stress test (public speaking task). ER22/23EK carriers had significantly lower cortisol responses to psychosocial stress compared with noncarriers. These findings provide evidence for the relevance of the ER22/23EK polymorphism in childhood HPA axis regulation. However, the small number of ER22/23EK subjects does not allow us to draw definitive conclusions about the genotypic effect.

The CRF system, stress, depression and anxiety-insights from human genetic studies

A concatenation of findings from preclinical and clinical studies support a preeminent function for the corticotropin-releasing factor (CRF) system in mediating the physiological response to external stressors and in the pathophysiology of anxiety and depression. Recently, human genetic studies have provided considerable support to several long-standing hypotheses of mood and anxiety disorders, including the CRF hypothesis. These data, reviewed in this report, are congruent with the hypothesis that this system is of paramount importance in mediating stress-related psychopathology. More specifically, variants in the gene encoding the CRF(1) receptor interact with adverse environmental factors to predict risk for stress-related psychiatric disorders. In-depth characterization of these variants will likely be important in furthering our understanding of the long-term consequences of adverse experience.

Depression and antidepressants: molecular and cellular aspects

Clinical depression is viewed as a physical and psychic disease process having a neuropathological basis, although a clear understanding of its ethiopathology is still missing. The observation that depressive symptoms are influenced by pharmacological manipulation of monoamines led to the hypothesis that depression results from reduced availability or functional deficiency of monoaminergic transmitters in some cerebral regions. However, there are limitations to current monoamine theories related to mood disorders. Recently, a growing body of experimental data has showed that other classes of endogenous compounds, such as neuropeptides and amino acids, may play a significant role in the pathophysiology of affective disorders. With the development of neuroscience, neuronal networks and intracellular pathways have been identified and characterized, describing the existence of the interaction between monoamines and receptors in turn able to modulate the expression of intracellular proteins and neurotrophic factors, suggesting that depression/antidepressants may be intermingled with neurogenesis/neurodegenerative processes.

Genetic variation in the hypothalamic-pituitary-adrenal stress axis influences susceptibility to musculoskeletal pain: results from the EPIFUND study

OBJECTIVES

To determine if genetic variation in genes in the hypothalamic-pituitary-adrenal (HPA) axis, the primary stress response system, influences susceptibility to developing musculoskeletal pain.

METHODS

Pain and comorbidity data was collected at three time points in a prospective population-based cohort study. Pairwise tagging single nucleotide polymorphisms (SNPs) were selected and genotyped for seven genes. Genetic association analysis was carried out using zero-inflated negative binomial regression to test for association between SNPs and the maximum number of pain sites across the three time points in participants reporting pain, reported as proportional changes with 95% CIs. SNPs were also tested for association with chronic widespread pain (CWP) using logistic regression reporting odds ratios and 95% CI.

RESULTS

A total of 75 SNPs were successfully genotyped in 994 participants including 164 cases with persistent CWP and 172 pain-free controls. Multiple SNPs in SERPINA6 were associated with the maximum number of pain sites; for example, each copy of the T allele of rs941601 was associated with having 16% (proportional change=1.16, 95% CI 1.04 to 1.28, p=0.006) more pain sites compared to participants with the CC genotype. SERPINA6 gene SNPs were also associated with CWP. Significant associations between the maximum number of pain sites and SNPs in the CRHBP and POMC genes were also observed and a SNP in MC2R was also associated with CWP. Associations between SNPs and comorbidity of poor sleep quality and depression explained some of the associations observed.

CONCLUSIONS

Genetic variation in HPA axis genes was associated with musculoskeletal pain; however, some of the associations were explained by comorbidities. Replication of these findings is required in independent cohorts.

Meta-analyses of genetic studies on major depressive disorder

The genetic basis of major depressive disorder (MDD) has been investigated extensively, but the identification of MDD genes has been hampered by conflicting results from underpowered studies. We review all MDD case-control genetic association studies published before June 2007 and perform meta-analyses for polymorphisms that had been investigated in at least three studies. The study selection and data extraction were performed in duplicate by two independent investigators. The 183 papers that met our criteria studied 393 polymorphisms in 102 genes. Twenty-two polymorphisms (6%) were investigated in at least three studies. Seven polymorphisms had been evaluated in previous meta-analyses, 5 of these had new data available. Hence, we performed meta-analyses for 20 polymorphisms in 18 genes. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Statistically significant associations were found for the APOE varepsilon2 (OR, 0.51), GNB3 825T (OR, 1.38), MTHFR 677T (OR, 1.20), SLC6A4 44 bp Ins/Del S (OR, 1.11) alleles and the SLC6A3 40 bpVNTR 9/10 genotype (OR, 2.06). To date, there is statistically significant evidence for six MDD susceptibility genes (APOE, DRD4, GNB3, MTHFR, SLC6A3 and SLC6A4).

Experiential and genetic contributions to depressive- and anxiety-like disorders: clinical and experimental studies

Stressful events have been implicated in the precipitation of depression and anxiety. These disorders may evolve owing to one or more of an array of neuronal changes that occur in several brain regions. It seems likely that these stressor-provoked neurochemical alterations are moderated by genetic determinants, as well as by a constellation of experiential and environmental factors. Indeed, animal studies have shown that vulnerability to depressive-like behaviors involve mechanisms similar to those associated with human depression (e.g., altered serotonin, corticotropin releasing hormone and their receptors, growth factors), and that the effects of stressors are influenced by previous stressor experiences, particularly those encountered early in life. These stressor effects might reflect sensitization of neuronal functioning, phenotypic changes of processes that lead to neurochemical release or receptor sensitivity, or epigenetic processes that modify expression of specific genes associated with stressor reactivity. It is suggested that depression is a life-long disorder, which even after effective treatment, has a high rate of re-occurrence owing to sensitized processes or epigenetic factors that promote persistent alterations of gene expression.

Corticotropin-releasing factor (CRF) in stress and disease: a review of literature and treatment perspectives with special emphasis on psychiatric disorders

The CRF family of neuropeptides and receptors is involved in a variety of stress responses, in the regulation of appetite, metabolic and inflammatory processes as well as intestinal movements. From a primarily psychiatric perspective, the present paper reviews the literature on its anatomy, physiology and its involvement in psychiatric, neurological and inflammatory diseases. Finally, recent developments in the pharmacological aspects of CRF in these diseases are reviewed.

Genetic variability at HPA axis in major depression and clinical response to antidepressant treatment

BACKGROUND

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been observed in major depression. Normalization of HPA axis has been suggested to play a role in the mechanisms of action of antidepressants. Our aim was to investigate the influence of genetic variants in CRHR1, CRHR2, CRH-BP and FKBP5 genes on both the vulnerability for depression and the response to antidepressant treatment.

METHODS

The sample consisted of 159 depressive outpatients and 96 healthy controls of Spanish origin. Patients were assessed for clinical features including, among others, age of onset, seasonality or suicidal behavior. The episode was treated with citalopram and followed along 12 weeks. Severity of symptoms was evaluated at the inclusion and then monthly along the follow-up using a 21-item Hamilton Depression Rating Score (HDRS). SNPs were assayed using Applied Biosystems SNaP-Shot and TaqMan technology.

RESULTS

rs110402, in CRHR1 gene, was associated with an increased risk to present a seasonal pattern and an early age of onset of the first depressive episode. Allele G carriers of rs2270007 of CRHR2 gene, showed a worse overall response to citalopram along time of follow-up (Genotype effect F=7.45, P=0.007). G allele carriers showed 2.93 increased risk (95% CI [1.24-6.90]) for non-responding at 4th week to citalopram treatment (chi(2)=7.59, df=1, P=0.006).

LIMITATIONS

On the light of the moderate sample size, associations based on the mentioned polymorphisms need to be considered with caution and require further replication studies in other samples.

CONCLUSIONS

Variability at genes encoding proteins with a pivotal role in HPA axis regulation seems to influence i) the expression of severity variables of the depressive spectrum including early age of onset or a seasonal pattern and ii) the interindividual variation in clinical response to SSRI antidepressants.

Single nucleotide polymorphism analysis of corticotropin-releasing factor-binding protein gene in bipolar disorder

Corticotropin-releasing factor-binding protein regulates the availability of free corticotropin-releasing factor and is a functional candidate gene for affective disorders. The aim of this study was to examine the association between polymorphisms in CRF-BP gene and bipolar disorder in an isolated Swedish population. One hundred and eighty-two patients with bipolar I disorder and 333 controls from Northern Sweden were included in the study. Five single nucleotide polymorphisms and a deletion polymorphism in the CRF-BP gene were genotyped. The haplotype block structure of the gene was considered and the expectation maximization algorithm was adopted to estimate the haplotype frequencies. As a result, there were no significant associations of the different polymorphisms in the CRF-BP gene with bipolar disorder. In conclusion, this study in an isolated Swedish population does not support a role for the CRF-BP gene in the vulnerability for bipolar disorder.

Consensus paper of the WFSBP Task Force on Biological Markers: biological markers in depression

Biological markers for depression are of great interest to aid in elucidating the causes of major depression. We assess currently available biological markers to query their validity for aiding in the diagnosis of major depression. We specifically focus on neurotrophic factors, serotonergic markers, biochemical markers, immunological markers, neuroimaging, neurophysiological findings, and neuropsychological markers. We delineate the most robust biological markers of major depression. These include decreased platelet imipramine binding, decreased 5-HT1A receptor expression, increase of soluble interleukin-2 receptor and interleukin-6 in serum, decreased brain-derived neurotrophic factor in serum, hypocholesterolemia, low blood folate levels, and impaired suppression of the dexamethasone suppression test. To date, however, none of these markers are sufficiently specific to contribute to the diagnosis of major depression. Thus, with regard to new diagnostic manuals such as DSM-V and ICD-11 which are currently assessing whether biological markers may be included in diagnostic criteria, no biological markers for major depression are currently available for inclusion in the diagnostic criteria.

Single nucleotide polymorphism analysis of corticotropin-releasing factor-binding protein gene in recurrent major depressive disorder

Corticotropin-releasing factor-binding protein (CRF-BP) regulates the availability of free CRF and is a functional candidate gene for affective disorders. Previous research showed an association between polymorphisms in the CRF-BP gene and recurrent major depression (MDD) in a Swedish sample. The purpose of the current study was to re-evaluate the previous findings in an extended Swedish sample and in an independent Belgian sample of patients with recurrent MDD and in control samples. In total, 317 patients and 696 control individuals were included. Five single nucleotide polymorphisms (SNPs) and a deletion polymorphism in the CRF-BP gene were genotyped and the haplotype block structure of the gene was assessed. In the extended Swedish population, there was a trend towards an association between two SNPs and MDD. The subsequent gender analysis showed significant associations of three SNPs (CRF-BPs2 T; CRF-BPs11 T and CRF-BPs12 C) and haplotype G_T_C_T_C with MDD in Swedish males. However, these findings did not withstand correction for multiple testing and there were no significant SNP or haplotype associations in the Belgian MDD sample. In conclusion, this study does not provide confirmatory evidence for a role of the CRF-BP gene in the vulnerability for MDD in general. The association between genetic CRF-BP variants and MDD may be sexually dimorphic, but this issue requires further investigation in a larger sample.

Role of corticotropin releasing factor in anxiety disorders: a translational research perspective

Anxiety disorders are a group of mental disorders that include generalized anxiety disorder (GAD), panic disorder, phobic disorders (e.g., specific phobias, agoraphobia, social phobia) and posttraumatic stress disorder (PTSD). Anxiety disorders are among the most common of all mental disorders and, when coupled with an awareness of the disability and reduced quality of life they convey, they must be recognized as a serious public health problem. Over 20 years of preclinical studies point to a role for the CRF system in anxiety and stress responses. Clinical studies have supported a model of CRF dysfunction in depression and more recently a potential contribution to specific anxiety disorders (i.e., panic disorder and PTSD). Much work remains in both the clinical and preclinical fields to inform models of CRF function and its contribution to anxiety. First, we will review the current findings of CRF and HPA axis abnormalities in anxiety disorders. Second, we will discuss startle reflex measures as a tool for translational research to determine the role of the CRF system in development and maintenance of clinical anxiety.

Decreased amygdala CRF-binding protein mRNA in post-mortem tissue from male but not female bipolar and schizophrenic subjects

Stressful life events are commonly associated with the onset and maintenance of psychopathology and much research has focused on the role of the corticotropin-releasing factor (CRF) system in mediating psychopathology. Since CRF serves to integrate the stress response, it is possible that the CRF system plays a role as a neurochemical linkage between stress and psychopathology. CRF-binding protein (CRF-BP) is thought to modulate CRF activity by decreasing its actions. Therefore, in some psychopathological states, alterations in CRF-BP function may contribute to dysregulation of the CRF system. Since the amygdala CRF system mediates stress- and anxiety-related behaviors and alterations in amygdala function are associated with psychopathology, we examined amygdala CRF-BP gene expression in post-mortem brains from subjects with major depression, bipolar disorder, and schizophrenia as well as in controls. In addition to characterizing the anatomic distribution of CRF-BP mRNA in the human amygdala and medial temporal lobe region, we found a significant decrease in CRF-BP mRNA levels in the basolateral amygdala of male bipolar and male schizophrenic subjects and the lateral amygdala of male bipolar subjects. These results raise the possibility that men with decreased amygdala CRF-BP may be more vulnerable to the effects of stress exposure on the etiology or maintenance of bipolar disorder or schizophrenia.

Corticotropin-releasing factor (CRF), but not corticosterone, increases basolateral amygdala CRF-binding protein

Corticotropin-releasing factor (CRF) is a key mediator of the behavioral, autonomic, and endocrine responses to stress. CRF binds two receptors and a CRF-binding protein (CRF-BP), which may inactivate or modulate the actions of CRF at its receptors. The amygdala is an important anatomical substrate for CRF and contains CRF, its receptors, and CRF-BP. Our previous studies demonstrated that acute stress increases basolateral amygdala (BLA) CRF-BP mRNA. However, factors that may be responsible for this increase remain unclear. Both CRF and corticosterone are released during stress and are known to increase CRF-BP in vitro. However, the effects of these agents in vivo on brain CRF-BP have not been studied. Therefore, we examined the effects of CRF and corticosterone administration on BLA CRF-BP mRNA in rats. The findings demonstrate that intracerebroventricular CRF (5 microg) significantly increases BLA CRF-BP mRNA 9 h post-infusion, a time point consistent with that observed for the effects of acute stress-induced increases in CRF-BP. In contrast, injection of corticosterone at a dose mimicking acute stress (6.5 mg/kg sc) failed to increase BLA CRF-BP mRNA 9 h post-injection. Surprisingly, two different CRF antagonists failed to block CRF-induced increases in CRF-BP mRNA. These results suggest that CRF, but not corticosterone, may be responsible for stress-induced increases in BLA CRF-BP gene expression. Furthermore, this effect appears to be mediated by mechanisms other than the identified CRF receptors.

Glucocorticoid receptor gene-based SNP analysis in patients with recurrent major depression

Dysregulation of the hypothalamic-pituitary-adrenal axis, one of the stress-response systems, is one of the key neurobiological features of major depression (MDD). Data supporting the notion that glucocorticoid-mediated feedback inhibition is impaired in MDD come from a multitude of studies demonstrating nonsuppression of cortisol secretion following administration of the synthetic glucocorticoid dexamethasone. We examined whether genetic variations in the glucocorticoid receptor gene (Nuclear Receptor Subfamily 3, Group C, Member 1; NR3C1) could be associated with increased susceptibility for MDD using a whole gene-based association analysis of single nucleotide polymorphisms (SNPs). Four SNPs were identified in NR3C1 and genotyped in two well-diagnosed samples of patients with MDD ascertained in Belgium and northern Sweden, and matched control samples. In total, 314 MDD patients and 354 control individuals were included in the study. In the Belgian sample, we observed significant allele (p=0.02) and genotype (p=0.02) association with an SNP in the promoter region (NR3C1-1); in the Swedish sample, we observed significant allele (p=0.02) and genotype (p=0.02) association with the R23K SNP. The haplotype association studies showed modest evidence for an involvement of the 5' region of the NR3C1 gene in the genetic vulnerability for MDD. This study suggests that polymorphisms in the 5' region of the NR3C1 gene may play a role in the genetic vulnerability for MDD.

Stress and depression-induced immune dysfunction: implications for the development and progression of cancer

The persistent activation of the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal-medullary axes in chronic stress response and in depression impairs the immune response and contributes to the development and progression of some types of cancer. This overview presents results from experimental animal models, human studies, and clinical evidence that various cellular and molecular immunological parameters are compromised in chronic stress and depression. At the cellular level, stressed and depressed patients had overall leukocytosis, high concentrations of circulating neutrophils, reduced mitogen-stimulated lymphocyte proliferation and neutrophil phagocytosis. At the molecular level, high levels of serum basal cortisol, acute phase proteins, specific antibodies against herpes simplex virus type 1 and Epstein Barr virus, plasma concentration of interleukins IL-1, IL-6, and TNF-alpha, and a shift in the balance of Th1 and Th2 immune response were observed. Both stress and depression were associated with the decreased cytotoxic T-cell and natural killer cell activities affecting the processes of the immune surveillance of tumours, and the events that modulate the development and the accumulation of somatic mutations and genomic instability. DNA damage, growth and angiogenic factors, proteases, matrix metalloproteinases, and reactive oxygen species were also related to the chronic stress response and depression. Behavioural strategies, psychological, and psychopharmacotherapeutic interventions that enhance effective coping and reduce affective distress showed beneficial effects in cancer patients. A better understanding of the bidirectional communication between the neuroendocrine and immune systems could contribute to novel clinical and treatment strategies in oncology.

Corticotropin-releasing factor-binding protein, stress and major depression

Major depressive disorder (MDD) is characterized by a dysregulation of the stress response system. A corticotropin-releasing factor (CRF) hyperdrive is a consistent and well-documented finding. CRF-binding protein (CRF-BP) may play a role in the pathogenesis of MDD. CRF-BP reduces the availability of CRF by binding free CRF and inhibits CRF function at the pituitary level. Moreover, CRF-BP expression increases in the pituitary and amygdala in response to acute stress, providing an additional feedback mechanism to maintain the homeostasis of the stress response. There are different regulatory elements of the expression of CRF-BP gene that are implicated in the pathophysiology of MDD, including CRF, glucocorticoids, cytokines and estrogens. A specific haplotype within the CRF-BP gene has been associated with MDD, but confirmation of this finding is necessary. Currently, the possible role of CRF-BP in the pathophysiology of conditions that have been associated with a hypofunction of the CRF system and immune dysfunctions is unclear. Implications of the function of CRF-BP for therapeutic strategies in MDD are being discussed. An important advantage of ligands that target CRF-BP is that concentrations of free CRF can be altered without acting directly on the transmission of CRF through its receptor.

Candidate genes for antidepressant response to selective serotonin reuptake inhibitors

Selective serotonin reuptake inhibitors (SSRIs) can safely and successfully treat major depression, although a substantial number of patients benefit only partially or not at all from treatment. Genetic polymorphisms may play a major role in determining the response to SSRI treatment. Nonetheless, it is likely that efficacy is determined by multiple genes, with individual genetic polymorphisms having a limited effect size. Initial studies have identified the promoter polymorphism in the gene coding for the serotonin reuptake transporter as moderating efficacy for several SSRIs. The goal of this review is to suggest additional plausible polymorphisms that may be involved in antidepressant efficacy. These include genes affecting intracellular transductional cascades; neuronal growth factors; stress-related hormones, such as corticotropin-releasing hormone and glucocorticoid receptors; ion channels and synaptic efficacy; and adaptations of monoaminergic pathways. Association analyses to examine these candidate genes may facilitate identification of patients for targeted alternative therapies. Determining which genes are involved may also assist in identifying future, novel treatments.

The effects of acute stress on the regulation of central and basolateral amygdala CRF-binding protein gene expression

Corticotropin-releasing factor (CRF) is a key mediator of the behavioral, autonomic, and endocrine responses to stress. CRF binds two receptors and a CRF-binding protein (CRF-BP), which may inactivate or modulate the actions of CRF at its receptors. The amygdala is an important anatomical substrate for CRF and contains CRF, its receptors, and CRF-BP. Few studies have examined the effects of acute stress on the regulation of amygdala CRF-BP with other CRF system genes. Therefore, we examined the time course of the effects of acute restraint stress on central (CeA) and basolateral (BLA) amygdala CRF system genes. Consistent with our previous study, acute stress increased BLA CRF-BP mRNA shortly after stress offset. Surprisingly, BLA CRF-BP mRNA remained elevated up to 21 h after the stressor. This effect was selective in the BLA as stress did not alter CeA CRF-BP mRNA, and there were no changes in CRF or CRF receptor mRNAs in either amygdala nucleus. These results suggest that alterations in BLA CRF-BP gene expression are a primary response of the BLA/CeA CRF system to acute stress. Because CRF-BP can modulate CRF action, changes in amygdala CRF-BP levels after stress exposure may affect the ability of an organism to adapt to future stressors.

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.

Discovering endophenotypes for major depression

The limited success of genetic studies of major depression has raised questions concerning the definition of genetically relevant phenotypes. This paper presents strategies to improve the phenotypic definition of major depression by proposing endophenotypes at two levels: First, dissecting the depressive phenotype into key components results in narrow definitions of putative psychopathological endophenotypes: mood bias toward negative emotions, impaired reward function, impaired learning and memory, neurovegetative signs, impaired diurnal variation, impaired executive cognitive function, psychomotor change, and increased stress sensitivity. A review of the recent literature on neurobiological and genetic findings associated with these components is given. Second, the most consistent heritable biological markers of major depression are proposed as biological endophenotypes for genetic studies: REM sleep abnormalities, functional and structural brain abnormalities, dysfunctions in serotonergic, catecholaminergic, hypothalamic-pituitary-adrenocortical axis, and CRH systems, and intracellular signal transduction endophenotypes. The associations among the psychopathological and biological endophenotypes are discussed with respect to specificity, temporal stability, heritability, familiality, and clinical and biological plausibility. Finally, the case is made for the development of a new classification system in order to reduce the heterogeneity of depression representing a major impediment to elucidating the genetic and neurobiological basis of this common, severe, and often life-threatening illness.

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.