Patient-control association study of substance P-related genes in unipolar and bipolar affective disorders

Recent advances in the molecular signaling pathways of Substance P in Alzheimer's disease: Link to neuroinflammation associated with toll-like receptors

A significant quantity of substance P (SP) and its receptor, the neurokinin 1 (NK1) receptors are found in the brain. SP is a neuropeptide distributed in the central nervous system and functions as a neurotransmitter, neuromodulator, and neurotrophic factor. The concentrations of SP in the brain and cerebrospinal fluid fluctuate in individuals with Alzheimer's disease (AD). SP is an endogenous ligand for NK1 receptor, enhancing the expression of toll-like receptors (TLR) and vice versa. So, both pathways are interconnected, where activation of one pathway activates the second pathway. Researchers have observed the interaction of TLR with SP in the pathophysiology of AD. Thus, this review discusses various TLRs involved in regulating amyloid processing and its interaction with SP in AD. Further, in AD pathology, SP can regulate the non-amyloidogenic pathway. Recent studies have also demonstrated the capacity of SP in regulating voltage-gated potassium channel currents, emphasizing SP's neuroprotective ability. Therefore, we corroborate the findings linking the SP, NK1R, and TLRs in AD.

Signaling pathways and genetics of brain Renin angiotensin system in psychiatric disorders: State of the art

Along the conventional pathways, Renin-angiotensin system (RAS) plays a key role in the physiology of the CNS and pathogenesis of psychiatric diseases. RAS is a complex regulatory pathway which is composed of several peptides and receptors and comprises two counter-regulatory axes. The classical (ACE1/AngII/AT1 receptor) axis and the contemporary (ACE2/Ang (1-7)/Mas receptor) axis. The genes coding for elements of both axes have been broadly studied. Numerous functional polymorphisms on components of RAS have been identified to serve as informative disease and treatment markers. This review summarizes the role of each peptide and receptor in the pathophysiology of psychiatric disorders (depression, bipolar disorders and schizophrenia), followed by a concise look at the role of genetic polymorphism of the RAS in the pathophysiology of these disorders.

The Renin Angiotensin System and Bipolar Disorder: A Systematic Review

Bipolar Disorder (BD) is a chronic a multifactorial psychiatric illness that affects mood, cognition, and functioning. BD is associated with several psychiatric conditions as well clinical comorbidities, particularly cardiovascular diseases. The neurobiology of BD is complex and multifactorial and several systems have been implicated. Considering that the Renin Angiotensin System (RAS) plays an important role in cardiovascular diseases and that recently evidence has suggested its role in psychiatric disorders, the aim of the present study is to summarize and to discuss recent findings related to the modulation of RAS components in BD. A systematic search of the literature using the electronic databases MEDLINE and LILACS was conducted through March 2019. The search terms were: "Bipolar Disorder"; "Renin Angiotensin System"; "Angiotensin 2"; "Angiotensin receptors"; "Angiotensin 1-7"; "ACE"; "ACE2"; "Mas Receptor". We included original studies assessing RAS in BD patients. Two hundred twenty-two citations were initially retrieved. Eleven studies were included in our systematic review. In the majority of studies (6 of 8), the ACE insertion/deletion (I/D) polymorphism did not differ between BD patients and controls. BD patients presented higher plasma renin activity in comparison with controls. The studies evaluating the RAS molecules in BD are very scarce and heterogeneous. The literature suggests a potential role of RAS in BD. Further studies are necessary to investigate this relationship.

D allele of insertion/deletion polymorphism at angiotensin-converting enzyme gene is associated with reduced prevalence and severity of depression among Chinese adolescents at early stage after Wenchuan earthquake

OBJECTIVE

The purpose of the present study was to longitudinally investigate the association of insertion/deletion (I/D) polymorphism at angiotensin-converting enzyme gene (ACE) with depression in Chinese adolescents experiencing the 2008 Wenchuan earthquake.

METHODS

Variants of ACE I/D were identified by polymerase chain reaction and verified by DNA sequencing. Depression symptoms were assessed by the Beck Depression Inventory (BDI) among high school students at 6, 12 and 18 months after the earthquake.

RESULTS

The D-allele carriers had lower depression prevalence than II homozygotes at 6, 12 and 18 months after the earthquake only in females, but not in males. Meanwhile, BDI scores were reduced in the female D-allele carriers when compared with those in the female II homozygotes at 6 and12 months after the earthquake. In addition, ACE I/D was found to be the predictors of BDI scores and depression prevalence at 6 and 12 months after the earthquake.

CONCLUSIONS

These results suggest that the association of ACE I/D with depression are longitudinally different in Chinese Han adolescents after the 2008 Wenchuan earthquake. The D allele may be associated with reduced depression prevalence and severity in female adolescents in the early stage of depression rehabilitation during the follow-up.

Neurokinin (NK)-1 receptor expression in monocytes from bipolar disorder patients: a pilot study

BACKGROUND

Neurokinin 1 receptors (NK-1R) have been involved in several psychiatric disorders including major depression, but less is known for bipolar disorder (BD).

METHOD

We compared NK-1R expression and Substance P (SP) ability to induce NF-κB activation in monocytes from BD patients and healthy donors (HD), also looking for the effects of tobacco smoke. After informed written consent, 20 euthymic BD patients, either bipolar type 1 (BDI) or type 2 (BDII), and 14 age-matched healthy donors (HD) were enrolled. NK-1R expression in monocytes was evaluated by Western blot and expressed as the ratio between NK-1R and Na(+)/K(+)-ATPase protein expressions. NF-κB activation was assessed by measuring the nuclear content of the p50 subunit (ELISA kit).

RESULTS

NK-1R expression was significantly reduced (P<0.001) in monocytes from BD patients as compared to HD, with no major differences between BDI and BDII patients. Tobacco smoke enhanced NK-1R expression in HD, but not in BD patients. Un-stimulated monocytes from BD patients presented a constitutively higher (P<0.05) content of nuclear p50 subunit as compared to HD. SP and an NK-1R agonist induced NF-κB activation, with a higher effect in HD: this effect was receptor-mediated as it was abrogated by an NK-1R antagonist.

LIMITATIONS

As a pilot study enrolling 20 BD patients, an obvious limitation is the sample size.

CONCLUSIONS

Our results show the existence of a relevant alteration in NK-1R expression in BD patients and further suggest SP involvement in BD, so improving our understanding of the underlying mechanisms of this disease.

From pharmacogenetics to pharmacogenomics: the way toward the personalization of antidepressant treatment

OBJECTIVE

Major depressive disorder is the most common psychiatric disorder, worldwide, yet response and remission rates are still unsatisfactory. The identification of genetic predictors of antidepressant (AD) response could provide a promising opportunity to improve current AD efficacy through the personalization of treatment. The major steps and findings along this path are reviewed together with their clinical implications and limitations.

METHOD

We systematically reviewed the literature through MEDLINE and Embase database searches, using any word combination of "antidepressant," "gene," "polymorphism," "pharmacogenetics," "genome-wide association study," "GWAS," "response," and "adverse drug reactions." Experimental works and reviews published until March 2012 were collected and compared.

RESULTS

Numerous genes pertaining to several functional systems were associated with AD response. The more robust findings were found for the following genes: solute carrier family 6 (neurotransmitter transporter), member 4; serotonin receptor 1A and 2A; brain-derived neurotrophic factor; and catechol-O-methyltransferase. Genome-wide association studies (GWASs) provided many top markers, even if none of them reached genome-wide significance.

CONCLUSIONS

AD pharmacogenetics have not produced any knowledge applicable to routine clinical practice yet, as results were mainly inconsistent across studies. Despite this, the rising awareness about methodological deficits of past studies could allow for the identication of more suitable strategies, such as the integration of the GWAS approach with the candidate gene approach, and innovative methodologies, such as pathway analysis and study of depressive endophenotypes.

Angiotensin-converting enzyme gene variants are associated with both cortisol secretion and late-life depression

Angiotensin-converting enzyme (ACE) is assumed to influence the activity of the hypothalamic-pituitary-adrenocortical (HPA) axis, which shows hyperactivity in depressed patients. ACE could thus be a promising candidate gene for late-life depression but this has not been examined previously. Depression was assessed in 1005 persons aged at least 65 years, at baseline and over the 10-year follow-up. A clinical level of depression (DEP) was defined as having a score of > or =16 on the Centre for Epidemiology Studies-Depression scale or a diagnosis of current major depression based on the Mini International Neuropsychiatric Interview and according to DSM-IV criteria. Seven single-nucleotide polymorphisms (SNPs) in the ACE gene were genotyped and diurnal cortisol secretion, as an index of HPA axis activity, was measured. Multivariable analyses were adjusted for socio-demographic and vascular factors, cognitive impairment, and apolipoprotein E. Strong significant associations were found between all seven SNPs and DEP and, in particular, first-onset DEP in persons without a past history of depression (P-values ranging from 0.005 to 0.0004). These associations remained significant after correction for multiple testing. The genotypes that were associated with an increased risk of DEP were also significantly associated with an increase in cortisol secretion under stress conditions. Variants of the ACE gene influence cortisol secretion and appear as susceptibility factors for late-life depression in the elderly population. Whether this could represent a common pathophysiological mechanism linking HPA axis and late-life depression remains to be explored.

Association of angiotensin-converting enzyme (ACE) gene polymorphism with elevated serum ACE activity and major depression in an Iranian population

Genetic factors contribute substantially to the likelihood of developing major depressive disorder (MDD). The importance of renin-angiotensin system (RAS) elements in cognition and behaviour and their involvement in aetiology and treatment of depression imply that RAS gene polymorphism(s) associated with RAS overactivity might also be associated with depression. In the present study, genotype and allele frequencies of six common polymorphisms of genes encoding for RAS components were determined in DNAs extracted from venous blood of 191 depressed and 104 healthy individuals using polymerase chain reaction (PCR) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and serum angiotensin-converting enzyme (ACE) activity was assayed using a high-performance liquid chromatography (HPLC) method. The results showed, for the first time, that GG genotype of ACE A2350G was significantly associated with MDD among Iranian participants (P=0.001; odds ratio (OR)=6.2; 95% confidence interval (CI)=2.1-18.3). Significant higher serum ACE activity (P=0.0001) as well as higher diastolic blood pressure (P=0.036) were observed in depressed patients compared to the healthy control group. Depressed patients carrying GG genotype of the A2350G polymorphism had a significantly higher serum ACE activity (P=0.02) than individuals with either AA or AG genotype. In conclusion, this study supports the hypothesis of RAS overactivity in depression in that the genotype associated with higher serum ACE activity in an Iranian population was also associated with MDD.

DNA methylation analysis of the angiotensin converting enzyme (ACE) gene in major depression

BACKGROUND

The angiotensin converting enzyme (ACE) has been repeatedly discussed as susceptibility factor for major depression (MD) and the bi-directional relation between MD and cardiovascular disorders (CVD). In this context, functional polymorphisms of the ACE gene have been linked to depression, to antidepressant treatment response, to ACE serum concentrations, as well as to hypertension, myocardial infarction and CVD risk markers. The mostly investigated ACE Ins/Del polymorphism accounts for ~40%-50% of the ACE serum concentration variance, the remaining half is probably determined by other genetic, environmental or epigenetic factors, but these are poorly understood.

MATERIALS AND METHODS

The main aim of the present study was the analysis of the DNA methylation pattern in the regulatory region of the ACE gene in peripheral leukocytes of 81 MD patients and 81 healthy controls.

RESULTS

We detected intensive DNA methylation within a recently described, functional important region of the ACE gene promoter including hypermethylation in depressed patients (p = 0.008) and a significant inverse correlation between the ACE serum concentration and ACE promoter methylation frequency in the total sample (p = 0.02). Furthermore, a significant inverse correlation between the concentrations of the inflammatory CVD risk markers ICAM-1, E-selectin and P-selectin and the degree of ACE promoter methylation in MD patients could be demonstrated (p = 0.01 - 0.04).

CONCLUSION

The results of the present study suggest that aberrations in ACE promoter DNA methylation may be an underlying cause of MD and probably a common pathogenic factor for the bi-directional relationship between MD and cardiovascular disorders.

Genetic polymorphism of angiotensin I-converting enzyme (ACE), but not angiotensin II type I receptor (ATr1), has a gender-specific role in panic disorder

AIMS

Angiotensins were shown to have some role in the development of panic disorder (PD). In this study, we aimed to determine the frequency of polymorphisms in two angiotensin-related genes, angiotensin I-converting enzyme (ACE) and angiotensin II type I receptor (ATr1), in a sample of Turkish patients with PD and to evaluate their association with PD development.

METHODS

Polymerase chain reaction and restriction fragment length polymorphism was used to analyze ATr1 A1166C polymorphism, and only polymerase chain reaction was used to analyze functional ACE insertion/deletion polymorphism in 123 patients with PD and in 169 similarly aged disease-free controls.

RESULTS

 There was no significant difference in the genotype distribution between PD patients and controls for each polymorphism (P>0.05). Allele frequency of ACE insertion/deletion was borderline statistically significant between the groups (P=0.055; odds ratio: 1.39; 95% confidence interval: 0.99-1.95), and allele frequency of ATr1 A1166C was not significantly different between the groups (P=0.32; odds ratio: 0.81; 95% confidence interval: 0.53-1.22).

CONCLUSION

This study suggests that polymorphisms of ACE I/D and ATr1 A1166C are not associated with risk of PD in Turkish patients. However, in ACE insertion/deletion polymorphism, the insertion allele was found to be more frequent in the male subgroup of patients (χ²=4.61, P=0.032) than in controls, suggesting a potential male-specific role of the less active ACE insertion allele in the pathogenesis of PD.

Meta-analysis of ACE gene I/D polymorphism and bipolar disorder susceptibility

BACKGROUND

A number of studies have been conducted to explore the association between ACE gene insertion/deletion (I/D) polymorphism and bipolar disorder (BPD). However, the reported results were conflicting.

AIMS

The aim of our study was to find evidence on whether ACE gene I/D polymorphism is associated with BPD using a meta-analysis.

METHODS

Data were collected from the following electronic databases: Pubmed, Elsevier Science Direct, Cochrane Library, CBM, CNKI and Wanfang. Meta-analysis was performed for genotypes ID vs. II, DD vs. II, DD vs. ID + II, ID + DD vs. II, and D allele vs. I allele in a fixed/random effect model.

RESULTS

Seven studies that included data from 605 cases and 1541 controls were identified. When all groups were pooled, we did not detect the association of ACE gene I/D polymorphism with BPD (P > 0.05). In the subgroup analysis, we did not detect the association of ACE gene I/D polymorphism with BPD in Caucasians (P > 0.05). An association of ACE gene I/D polymorphism with BPD was found in Asians for the contrast of DD vs. ID + II (OR = 2.01, 95% CI 1.08-3.74, P = 0.03), but not for other contrasts (P > 0.05).

CONCLUSIONS

This meta-analysis suggests that there may be an association of ACE gene I/D polymorphism with BPD in Asians. Further studies are still needed in Asians.

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.

Adenosine A(2A) receptor gene: evidence for association of risk variants with panic disorder and anxious personality

Adenosine A(2A) receptors are suggested to play an important role in different brain circuits and pathways involved in anxiety reactions. A variant within the corresponding ADORA2A gene (rs5751876) increased the risk for panic disorder (PD), for elevated anxiety during challenge tests in healthy probands and for anxiety-related arousal in blood-injury phobia. These multiple effects may mirror a more general effect of the SNP on basic personality traits. In the present study we therefore aimed to replicate the original finding in a large PD sample and extend it by investigating an additional proband sample characterized for different anxiety-related personality scores. In addition, as rs5751876 is assumed not to be the disease variant itself but to be in linkage disequilibrium (LD) with the true functional polymorphism other SNPs of potentially functional relevance were identified by re-sequencing the whole gene including several newly identified regions of putative regulatory potential and analysed for their impact on PD and anxious personality. We were indeed able to replicate rs5751876 as risk factor for PD, particularly PD with agoraphobia. Rs5751876 and several other variants in high LD (rs5751862, rs2298383 and rs3761422) as well as the corresponding haplotypes were also associated with different anxiety-related personality scores (Bonferroni corrected P(all) < 0.05). Of these variants, rs2298383 shows functional potential based on in silico analyses and might therefore represent the true underlying causal variant. Our data provide further support for an important role of ADORA2A variants in the pathogenesis of anxiety disorders and anxious personality reflecting their potential as basic susceptibility factors.

Polymorphisms in the angiotensin-converting enzyme gene region predict coping styles in healthy adults and depressed patients

Dispositional coping styles are important moderators of the stress reaction and are altered in stress-related disorders like cardiovascular diseases and affective disorders. Heritability studies suggest a considerable genetic contribution to the interindividual variability in coping styles. Since the angiotensin-converting enzyme (ACE) gene has been described to be associated with the vulnerability for stress-related disorders and with altered stress hormone regulation, we investigated the ACE gene as potential candidate gene for coping styles. Five hundred forty one mentally healthy subjects and 194 patients suffering from depression participating in the Munich Antidepressant Response Signature (MARS) project were examined. Coping styles were assessed with a self-report questionnaire (German Stress Coping Questionnaire SVF78) measuring the individual coping style pattern in response to stressful situations. We genotyped 15 single nucleotide polymorphisms (SNPs) and the insertion/Deletion (I/D)-polymorphism in the ACE gene region and investigated their associations with coping styles. In healthy subjects, the highest association was observed between rs8066276, an intronic SNP of the ACE gene, and the coping factor Distraction. A further intronic SNP rs4305, not in linkage disequilibrium with rs8066276, showed an association with Devaluation/Defense. All associated copying styles can be categorized as potentially stress reducing factors (positive coping). Both SNPs were also found to be associated with positive coping styles in the patient sample; rs8066276 was associated with Devaluation/Defense, and rs4305 showed associations with Control. These results suggest that the ACE gene is involved in the development of coping strategies.

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).

Tachykinin receptor 1 variants associated with aggression in suicidal behavior

Substance P is involved in the modulation of depression, anxiety, and suicidal-related behaviors. We studied gene variants of Tachykinin Receptor 1 (TACR1-rs3771810, rs3771825, rs726506, rs1477157) in 167 German suicide attempters (affective spectrum n = 107, schizophrenia spectrum n = 35, borderline personality disorder n = 25), 92 Caucasian individuals who committed suicide and 312 German healthy subjects. Single markers and haplotype analysis in relation to suicidal behaviors (suicide attempters/completers) did not reveal any significant association. The rarest rs3771825 T allele however showed a marginal association with higher Reactive Aggression scores on the Questionnaire for Measuring Factors of Aggression (FAF) (F = 9.86, df = 1; P = 0.0017). Haplotype analyses confirmed the finding. Violence or impulsivity of suicide attempt and State-Trait Anger Expression Inventory (STAXI) scores were not associated with gene variants. In conclusion, our study suggests that TACR1 gene variants have no major influence on suicidal behavior but may modulate aggression features.

Renin-angiotensin-system gene polymorphisms and depression

Given the abundance of the renin-angiotensin system (RAS) components in the brain, their importance in behavior and cognition, and the data that implicates them in the etiology and treatment of depression, it is possible that those RAS gene polymorphisms associated with increased RAS activity may also be associated with depression. The frequencies of common polymorphisms of genes encoding for components of the RAS, namely angiotensinogen (M235T), angiotensin converting enzyme (ACE) (insertion, I; deletion, D), angiotensin receptor type I (A1166C), and angiotensin receptor type II (C3123A) were determined in DNA extracted from buccal cells from a Lebanese population of 132 depressed patients and their first-degree relative case-controls. The angiotensin receptor type 1 (A1166C) CC genotype was significantly associated with depression (p=0.036). None of the other common RAS-associated polymorphisms were significantly associated. The results support the hypothesis that increased RAS activity may increase relative risk of depression in that the angiotensin receptor type 1 (A1166C) CC genotype is associated with increased responsiveness to angiotensin II.