Bronchodilator response (BDR) is an important asthma phenotype that measures reversibility of airway obstruction by comparing lung function (i.e. FEV1) before and after the administration of a short-acting β2-agonist, the most common rescue medications used for the treatment of asthma. BDR also serves as a test of β2-agonist efficacy. BDR is a complex trait that is partly under genetic control. A genome-wide association study (GWAS) of BDR, quantified as percent change in baseline FEV1 after administration of a β2-agonist, was performed with 1,644 non-Hispanic white asthmatic subjects from six drug clinical trials: CAMP, LOCCS, LODO, a medication trial conducted by Sepracor, CARE, and ACRN. Data for 469,884 single-nucleotide polymorphisms (SNPs) were used to measure the association of SNPs with BDR using a linear regression model, while adjusting for age, sex, and height. Replication of primary P-values was attempted in 501 white subjects from SARP and 550 white subjects from DAG. Experimental evidence supporting the top gene was obtained via siRNA knockdown and Western blotting analyses. The lowest overall combined P-value was 9.7E-07 for SNP rs295137, near the SPATS2L gene. Among subjects in the primary analysis, those with rs295137 TT genotype had a median BDR of 16.0 (IQR = [6.2, 32.4]), while those with CC or TC genotypes had a median BDR of 10.9 (IQR = [5.0, 22.2]). SPATS2L mRNA knockdown resulted in increased β2-adrenergic receptor levels. Our results suggest that SPATS2L may be an important regulator of β2-adrenergic receptor down-regulation and that there is promise in gaining a better understanding of the biological mechanisms of differential response to β2-agonists through GWAS.
Bronchodilator response (BDR) is an important asthma phenotype that measures reversibility of airway obstruction by comparing lung function before and after the administration of short-acting β2-agonists, common medications used for asthma treatment. We performed a genome-wide association study of BDR with 1,644 white asthmatic subjects from six drug clinical trials and attempted to replicate these findings in 1,051 white subjects from two independent cohorts. The most significant associated variant was near the SPATS2L gene. We knocked down SPATS2L mRNA in human airway smooth muscle cells and found that β2-adrenergic receptor levels increased, suggesting that SPATS2L may be a regulator of BDR. Our results highlight the promise of pursuing GWAS results that do not necessarily reach genome-wide significance and are an example of how results from pharmacogenetic GWAS can be studied functionally.
To evaluate phenotypic and genetic variables associated with a poor long-term response to inhaled corticosteroid therapy for asthma, based independently on lung function changes or asthma exacerbations.
Materials & methods
We tested 17 phenotypic variables and polymorphisms in FCER2 and CRHR1 in 311 children (aged 5–12 years) randomized to a 4-year course of inhaled corticosteroid during the Childhood Asthma Management Program (CAMP).
Predictors of recurrent asthma exacerbations are distinct from predictors of poor lung function response. A history of prior asthma exacerbations, younger age and a higher IgE level (p < 0.05) are associated with recurrent exacerbations. By contrast, lower bronchodilator response to albuterol and the minor alleles of RS242941 in CRHR1 and T2206C in FCER2 (p < 0.05) are associated with poor lung function response. Poor lung function response does not increase the risk of exacerbations and vice versa (p = 0.72).
Genetic and phenotypic predictors of a poor long-term response to inhaled corticosteroids differ markedly depending on definition of outcome (based on exacerbations vs lung function). These findings are important in comparing outcomes of clinical trials and in designing future pharmacogenetic studies.
asthma; corticosteroid; exacerbation; lung function; pharmacogenetics
Variation in the corticotropin-releasing hormone receptor (CRHR1) gene has been shown to interact with early-life stress to predict adult depression. This study was conducted to determine whether CRHR1 polymorphisms interact with childhood maltreatment to predict HPA axis reactivity, which has been linked to both depression and early-life stress.
One-hundred twenty-nine White non-Hispanic adults completed the Childhood Trauma Questionaire, the dexamethasone/corticotropin-releasing hormone test, and provided blood samples for genotyping of two CRHR1 polymorphisms.
Both rs110402 and rs242924 (which were in tight linkage disequilibrium, D’=0.98) showed a significant interaction with maltreatment in the prediction of cortisol response to the Dex/CRH test (p<.05). For subjects with maltreatment, the GG genotype of each SNP was associated with elevated cortisol responses to the test.
Variation in the CRHR1 moderates the effect of childhood maltreatment on cortisol responses to the Dex/CRH test. Excessive HPA axis activation could represent a mechanism of interactions of risk genes with stress in the development of mood and anxiety disorders.
Cortisol; Dex/CRH test; HPA axis; genetics; CRHR1 gene; gene-environment interaction
Purpose of review
Patient response to the asthma drug classes, bronchodilators, inhaled corticosteroids and leukotriene modifiers, are characterized by a large degree of heterogeneity, which is attributable in part to genetic variation. Herein, we review and update the pharmacogenetics and pharmaogenomics of common asthma drugs.
Early studies suggest that bronchodilator reversibility and asthma worsening in patients on continuous short-acting and long-acting β-agonists are related to the Gly16Arg genotype for the ADRB2. More recent studies including genome-wide association studies implicate variants in other genes contribute to bronchodilator response heterogeneity and fail to replicate asthma worsening associated with continuous β-agonist use. Genetic determinants of the safety of long-acting β-agonist require further study. Variants in CRHR1, TBX21, and FCER2 contribute to variability in response for lung function, airways responsiveness, and exacerbations in patients taking inhaled corticosteroids. Variants in ALOX5, LTA4H, LTC4S, ABCC1, CYSLTR2, and SLCO2B1 contribute to variability in response to leukotriene modifiers.
Identification of novel variants that contribute to response heterogeneity supports future studies of single nucleotide polymorphism discovery and include gene expression and genome-wide association studies. Statistical models that predict the genomics of response to asthma drugs will complement single nucleotide polymorphism discovery in moving toward personalized medicine.
asthma; genes; personalized medicine; polymorphisms; response heterogeneity
Genetic inheritance and developmental life stress both contribute to major depressive disorder in adults. Child abuse and trauma alter the endogenous stress response, principally corticotropin-releasing hormone and its downstream effectors, suggesting that a gene × environment interaction at this locus may be important in depression.
To examine whether the effects of child abuse on adult depressive symptoms are moderated by genetic polymorphisms within the corticotropin-releasing hormone type 1 receptor (CRHR1) gene.
Association study examining gene × environment interactions between genetic polymorphisms at the CRHR1 locus and measures of child abuse on adult depressive symptoms.
General medical clinics of a large, public, urban hospital and Emory University, Atlanta, Georgia.
The primary participant population was 97.4% African American, of low socioeconomic status, and with high rates of lifetime trauma (n=422). A supportive independent sample (n=199) was distinct both ethnically (87.7% Caucasian) and socioeconomically (less impoverished).
Main Outcome Measures
Beck Depression Inventory scores and history of major depressive disorder by the Structured Clinical Interview for DSM-IV Axis I Disorders.
Fifteen single-nucleotide polymorphisms spanning 57 kilobases of the CRHR1 gene were examined. We found significant gene × environment interactions with multiple individual single-nucleotide polymorphisms (eg, rs110402, P=.008) as well as with a common haplotype spanning intron 1 (P <.001). Specific CRHR1 polymorphisms appeared to moderate the effect of child abuse on the risk for adult depressive symptoms. These protective effects were supported with similar findings in a second independent sample (n=199).
These data support the corticotropin-releasing hormone hypothesis of depression and suggest that a gene × environment interaction is important for the expression of depressive symptoms in adults with CRHR1 risk or protective alleles who have a history of child abuse.
Endophenotypes reflect more proximal effects of genes than diagnostic categories, hence providing a more powerful strategy in searching for genes involved in complex psychiatric disorders. There is strong evidence suggesting the P3 amplitude of the event-related potential (ERP) as an endophenotype for the risk of alcoholism and other disinhibitory disorders. Recent studies demonstrated a crucial role of corticotropin releasing hormone receptor 1 (CRHR1) in the environmental stress response and ethanol self-administration in animal models. The aim of the present study was to test the potential associations between single-nucleotide polymorphisms (SNPs) in the CRHR1 gene and the quantitative trait, P3 amplitude during the processing of visual target signals in an oddball paradigm, as well as alcohol dependence diagnosis.
We analyzed a sample from the Collaborative Study on the Genetics of Alcoholism (COGA) comprising 1049 Caucasian subjects from 209 families (including 472 alcohol-dependent individuals). Quantitative transmission disequilibrium test (QTDT) and family-based association test (FBAT) were used to test the association, and false discovery rate (FDR) was applied to correct for multiple comparisons.
Significant associations (p < 0.05) were found between the P3 amplitude and alcohol dependence with multiple SNPs in the CRHR1 gene.
Our results suggest that CRHR1 may be involved in modulating the P3 component of the ERP during information processing and in vulnerability to alcoholism. These findings underscore the utility of electrophysiology and the endophenotype approach in the genetic study of psychiatric disorders.
P3; Disinhibition; Endophenotype; Stress; Corticotropin Releasing Factor (CRF)
Corticotropin-releasing hormone (Crh) plays an important role in modulating physiological and behavioral responses to stress. Its actions are mediated through two receptors, Crhr1 and Crhr2. Urocortin (Ucn), a Crh-related neuropeptide and the postulated endogenous ligand for Crhr2, is a potential mediator of stress responses. We generated Ucn-deficient mice using embryonic stem cell technology to determine its role in stress-induced behavioral and autonomic responses. Unlike Crhr1- or Crhr2-deficient mice, Ucn-deficient mice exhibit normal anxiety-like behavior as well as autonomic regulation in response to stress. However, the mutant mice display an impaired acoustic startle response that is not due to an obvious hearing defect. Thus, our results suggest that Ucn does not play an essential role in stress-induced behavioral and autonomic responses. Ucn may modulate the acoustic startle response through the Ucn-expressing neuron projections from the region of the Edinger-Westphal nucleus.
Major depressive disorder (MDD) is a long-term, recurrent condition that often takes a chronic course. It seems imperative that research should be focused on gaining a better understanding of what predicts recurrent MDD. As a major mediator of the stress response, corticotropin-releasing-hormone receptor 1 (CRHR1) has been demonstrated to be an important contributor to the pathogenesis of MDD. In this study, we show a significant increase in the G-allele (rs242939) of the CRHR1 gene in the recurrent MDD group compared with the control group, and an overrepresentation of G-G-T hyplotype of the CRHR1 gene in recurrent MDD. We also demonstrate the interaction of the CRHR1 gene and negative life events in recurrent MDD. These results suggest that the CRHR1 gene could modify the susceptibility to developing recurrent MDD following negative life events in adulthood.
Short-acting inhaled β2-agonists such as albuterol are used for bronchodilation and are the mainstay of asthma treatment worldwide. There is significant variation in bronchodilator responsiveness to albuterol not only between individuals but also across racial/ethnic groups. The β2-adrenergic receptor (β2AR) is the target for β2-agonist drugs. The enzyme S-nitrosoglutathione reductase (GSNOR), which regulates levels of the endogenous bronchodilator S-nitrosoglutathione, has been shown to modulate the response to β2-agonists.
We hypothesized that there are pharmacogenetic interactions between GSNOR and β2AR gene variants which are associated with variable response to albuterol.
We performed family-based analyses to test for association between GSNOR gene variants and asthma and related phenotypes in 609 Puerto Rican and Mexican families with asthma. In addition, we tested these subjects for pharmacogenetic interaction between GSNOR and β2AR gene variants and responsiveness to albuterol using linear regression. Cell transfection experiments were performed to test the potential effect of the GSNOR gene variants.
Among Puerto Ricans, several GSNOR SNPs and a haplotype in the 3′UTR were significantly associated with increased risk for asthma and lower bronchodilator responsiveness (p = 0.04 to 0.007). The GSNOR risk haplotype affects expression of GSNOR mRNA and protein, suggesting a gain of function. Furthermore, gene-gene interaction analysis provided evidence of pharmacogenetic interaction between GSNOR and β2AR gene variants and the response to albuterol in Puerto Rican (p = 0.03), Mexican (p = 0.15) and combined Puerto Rican and Mexican asthmatics (p = 0.003). Specifically, GSNOR+17059*β2AR+46 genotype combinations (TG+GG*AG and TG+GG*GG) were associated with lower bronchodilator response.
Genotyping of GSNOR and β2AR genes may be a useful in identifying Latino subjects, who might benefit from adjuvant therapy for refractory asthma.
Asthma; Bronchodilator responsiveness; GSNO Reductase; β2-Adrenergic Receptor; Latinos; Gene-gene interaction; Polymorphisms; Pharmacogenetics
Variations of the corticotropin-releasing hormone receptor 1 (CRHR1) gene appear to moderate the development of depression after childhood trauma. Depression more frequently affects women than men. We examined sex differences in the effects of the CRHR1 gene on the relationship between childhood trauma and adult depression. We recruited 1,063 subjects from the waiting rooms of a public urban hospital. Childhood trauma exposure and symptoms of depression were assessed using dimensional rating scales. Subjects were genotyped for rs110402 within the CRHR1 gene. An independent sample of 78 subjects underwent clinical assessment, genotyping, and a dexamethasone/CRH test. The age range at recruitment was 18–77 years and 18–45, for the two studies respectively. In the hospital sample, the protective effect of the rs110402 A-allele against developing depression after childhood trauma was observed in men (N = 424), but not in women (N = 635). In the second sample, the rs110402 A-allele was associated with decreased cortisol response in the dexamethasone/CRH test only in men. In A-allele carriers with childhood trauma exposure women exhibited increased cortisol response compared men; there were no sex differences in A-allele carriers without trauma exposure. This effect may, however, not be related to gender differences per se, but to differences in the type of experienced abuse between men and women. CRHR × environment interactions in the hospital sample were observed with exposure to physical, but not sexual or emotional abuse. Physical abuse was the most common type of abuse in men in this cohort, while sexual abuse was most commonly suffered by women. Our results suggest that the CRHR1 gene may only moderate the effects of specific types of childhood trauma on depression. Gender differences in environmental exposures could thus be reflected in sex-specific CRHR1 × child abuse interactions.
CRH receptor; gene x environment interaction; depression; dex-CRH test; polymorphism; HPA-axis; endocrine; genetics
Endometriosis is considered as a benign aseptic inflammatory disease, characterised by the presence of ectopic endometrium-like tissue. Its symptoms (mostly pain and infertility) are reported as constant stressors. Corticotropin releasing hormone (CRH) and urocortin (UCN) are neuropeptides, strongly related to stress and inflammation. The effects of CRH and UCN are mediated through CRHR1 and CRHR2 receptors which are implicated in several reproductive functions acting as inflammatory components. However, the involvement of these molecules to endometriosis remains unknown. The aim of this study was to examine the expression of CRHR1 and CRHR2 in endometriotic sites and to compare the expression of CRHR1 and CRHR2 in eutopic endometrium of endometriotic women to that of healthy women. We further compared the expression of CRH, UCN, CRHR1 and CRHR2 in ectopic endometrium to that in eutopic endometrium of women with endometriosis. Endometrial biopsy specimens were taken from healthy women (10 patients) and endometrial and endometriotic biopsy specimens were taken from women with endometriosis (16 patients). Τhe expression of CRH, UCN, CRHR1, and CRHR2 was tested via RT-PCR, immunohistochemistry and Western blotting. This study shows for the first time that CRH and UCN receptor subtypes CRHR1β and CRHR2α are expressed in endometriotic sites and that they are more strongly expressed (p<0.01) in eutopic endometrium of women with endometriosis compared to healthy women endometrium at the mRNA and protein level. CRH, UCN, CRHR1 and CRHR2 mRNA were also more highly expressed in ectopic rather than eutopic endometrium (CRH, UCN, CRHR2α: p<0.01, CRHR1β: p<0.05) and protein (CRH and UCN: p<0.05, CRHR1 and CRHR2: p<0.01) in women with endometriosis. These data indicate that CRH and UCN might play an immunoregulatory role in endometriotic sites by affecting reproductive functions such as decidualization and implantation of women with endometriosis.
Gene × environment (G × E) interactions mediating depressive symptoms have been separately identified in the stress-sensitive serotonergic (5-HTTLPR) and corticotropin-releasing hormone (CRHR1) systems. Our objective was to examine whether the effects of child abuse are moderated by gene × gene (G × G) interactions between CRHR1 and 5-HTTLPR polymorphisms. We used an association study examining G × G × E interactions of CRHR1 and 5-HTTLPR polymorphisms and measures of child abuse on adult depressive symptomatology. The participant population (N = 1,392) was African-American, of low socioeconomic status (60% with <$1,000/month family income), and with high rates of childhood and lifetime trauma. Depressive symptoms were measured with Beck Depression Inventory (BDI) and history of Major Depression by Structure Clinical Interview based on DSM-IV (SCID). We first replicated an interaction of child abuse and 5-HTTLPR on lifetime SCID diagnosis of major depression in a subsample (N = 236) of the study population—the largest African-American 5-HTTLPR cohort reported to date. We then extended our previously reported interaction with both a CRHR1 SNP (rs110402) and TCA haplotype interacting with child abuse to predict current symptoms (N = 1,059; P = 0.0089). We found that the 5-HTTLPR S allele interacted with CRHR1 haplotypes and child abuse to predict current depressive symptoms (N = 856, P = 0.016). These data suggest that G × E interactions predictive of depressive symptoms may be differentially sensitive to levels of childhood trauma, and the effects of child abuse are moderated by genetic variation at both the CRHR1 and 5-HTTLPR loci and by their G × G interaction. © 2009 Wiley-Liss, Inc.
child abuse; childhood maltreatment; trauma; depression; PTSD; genetic; risk factor
Urocortin II (UcnII) is a neuropeptide that binds with high affinity to the corticotropin‐releasing hormone receptor 2 (CRHR2) in peripheral tissues. UcnII is synthesised in the intestine, but its role in human intestinal inflammation is largely unknown.
Responses of human colonic epithelial cells expressing CRHR2 to stimulation by UcnII were measured using ELISA, western blot analysis, real‐time reverse transcription‐PCR (RT‐PCR) and interleukin (IL)8 promoter activity. Expression levels of CRHR2 and UcnII in human colitis were determined by immunofluorescence and real‐time RT‐PCR in mucosal biopsies from patients with Crohn's and ulcerative colitis, and in human intestinal xenografts after exposure to Clostridium difficile toxin A.
It is reported here that expression of CRHR2 mRNA and protein in human colonic epithelial cells (HT‐29) are increased by exposure to C difficile toxin A or tumour necrosis factor (TNF)α. Stimulation of non‐transformed NCM460 colonocytes overexpressing CRHR2α receptor with UcnII resulted in a time‐ and concentration‐dependent increase in IL8 production. UcnII stimulation also led to activation of nuclear factor‐κB (NF‐κB) and mitogen‐acivated protein (MAP) kinase in these cells, as evidenced by degradation of IκBα and phosphorylation of the p65 subunit of NF‐κB and extracellularly regulated kinase (ERK) 1/2. Furthermore, expression of UcnII and CRHR2 mRNA was increased in mucosal samples of patients with inflammatory bowel disease, and after exposure of human intestinal xenografts to C difficile toxin A.
These results suggest that UcnII has pro‐inflammatory effects in human intestinal cells via the CRHR2α receptor and may play an important role in the pathophysiology of colitis in humans.
Although corticotropin-releasing hormone (CRH) and Fas ligand (FasL) have been documented in ovarian carcinoma, a clear association with tumour progression and immuno-escape has not been established. FasL plays an important role in promoting tumour cells' ability to counterattack immune cells. Here, we examined immunohistochemically the expression of CRH, CRHR1, CRHR2 and FasL in 47 human ovarian cancer cases. The ovarian cancer cell lines OvCa3 and A2780 were further used to test the hypothesis that CRH might contribute to the immune privilege of ovarian tumours, by modulating FasL expression on the cancer cells. We found that CRH, CRHR1, CRHR2 and FasL were expressed in 68.1, 70.2, 63.8 and 63.8% of the cases respectively. Positivity for CRH or FasL expression was associated with higher tumour stage. Finally, CRH increased the expression of FasL in OvCa3 and A2780 cells through CRHR1 thereby potentiated their ability to induce apoptosis of activated peripheral blood lymphocytes. Corticotropin-releasing hormone produced by human ovarian cancer might favour survival and progression of the tumour by promoting its immune privilege. These findings support the hypothesis that CRHR1 antagonists could potentially be used against ovarian cancer.
CRH; Fas ligand; ovarian cancer; immune privilege; apoptosis
A 900-KB inversion exists within a large region of conserved linkage disequilibrium (LD) on chromosome 17. CRHR1 is located within the inversion region and associated with inhaled corticosteroid response in asthma. We hypothesized that CRHR1 variants are in LD with the inversion, supporting a potential role for natural selection in the genetic response to corticosteroids. We genotyped 6 single nucleotide polymorphisms (SNPs) spanning chr17:40,410,565–42,372,240, including 4 SNPs defining inversion status. Similar allele frequencies and strong LD were noted between the inversion and a CRHR1 SNP previously associated with lung function response to inhaled corticosteroids. Each inversion-defining SNP was strongly associated with inhaled corticosteroid response in adult asthma (p-values 0.002–0.005). The CRHR1 response to inhaled corticosteroids may thus be explained by natural selection resulting from inversion status or by long-range LD with another gene. Additional pharmacogenetic investigations into to regions of chromosomal diversity, including copy number variation and inversions, are warranted.
CRHR1; tau haplotype; MAPT; inversion; asthma; corticosteroid; pharmacogenetics
Corticotropin-releasing hormone (CRH) and its receptor, CRH receptor-1 (CRHR1), have a key role in alcoholism. Especially, post-dependent and stress-induced alcohol intake involve CRH/CRHR1 signaling within extra-hypothalamic structures, but a contribution of the hypothalamic–pituitary–adrenal (HPA) axis activity might be involved as well. Here we examined the role of CRHR1 in various drinking conditions in relation to HPA and extra-HPA sites, and studied relapse-like drinking behavior in the alcohol deprivation model (ADE). To dissect CRH/CRHR1 extra-HPA and HPA signaling on a molecular level, a conditional brain-specific Crhr1-knockout (Crhr1NestinCre) and a global knockout mouse line were studied for basal alcohol drinking, stress-induced alcohol consumption, deprivation-induced intake, and escalated alcohol consumption in the post-dependent state. In a second set of experiments, we tested CRHR1 antagonists in the ADE model. Stress-induced augmentation of alcohol intake was lower in Crhr1NestinCre mice as compared with control animals. Crhr1NestinCre mice were also resistant to escalation of alcohol intake in the post-dependent state. Contrarily, global Crhr1 knockouts showed enhanced stress-induced alcohol consumption and a more pronounced escalation of intake in the post-dependent state than their control littermates. Basal intake and deprivation-induced intake were unaltered in both knockout models when compared with their respective controls. In line with these findings, CRHR1 antagonists did not affect relapse-like drinking after a deprivation period in rats. We conclude that CRH/CRHR1 extra-HPA and HPA signaling may have opposing effects on stress-related alcohol consumption. CRHR1 does not have a role in basal alcohol intake or relapse-like drinking situations with a low stress load.
alcoholism; stress; relapse; post-dependent drinking; alcohol deprivation effect (ADE); conditional Crhr1NestinCre-knockout mice; alcohol and alcoholism; biological psychiatry; neurochemistry; animal models; stress; relapse; post-dependent drinking; alcohol deprivation effect; CRH
A previous study reported a gene × environment interaction in which a haplotype in the corticotropin-releasing hormone receptor 1 gene (CRHR1) was associated with protection against adult depressive symptoms in individuals who were maltreated as children (as assessed by the Childhood Trauma Questionnaire [CTQ]).
To replicate the interaction between childhood maltreatment and a TAT haplotype formed by rs7209436, rs110402, and rs242924 in CRHR1, predicting adult depression.
Two prospective longitudinal cohort studies.
England and New Zealand.
Participants in the first sample were women in the E-Risk Study (N= 1116), followed up to age 40 years with 96% retention. Participants in the second sample were men and women in the Dunedin Study (N= 1037), followed up to age 32 years with 96% retention.
Main Outcome Measure
Research diagnoses of pastyear and recurrent major depressive disorder.
In the E-Risk Study, the TAT haplotype was associated with a significant protective effect. In this effect, women who reported childhood maltreatment on the CTQ were protected against depression. In the Dunedin Study, which used a different type of measure of maltreatment, this finding was not replicated.
A haplotype in CRHR1 has been suggested to exert a protective effect against adult depression among research participants who reported maltreatment on the CTQ, a measure that elicits emotional memories. This suggests the hypothesis that CRHR1’s protective effect may relate to its function in the consolidation of memories of emotionally arousing experiences.
Bronchodilator response tests measure the effect of β2-agonists, the most commonly used short-acting reliever drugs for asthma. We sought to relate candidate gene SNP data with bronchodilator response and measure the predictive accuracy of a model constructed with genetic variants.
Materials & methods
Bayesian networks, multivariate models that are able to account for simultaneous associations and interactions among variables, were used to create a predictive model of bronchodilator response using candidate gene SNP data from 308 Childhood Asthma Management Program Caucasian subjects.
The model found that 15 SNPs in 15 genes predict bronchodilator response with fair accuracy, as established by a fivefold cross-validation area under the receiver-operating characteristic curve of 0.75 (standard error: 0.03).
Bayesian networks are an attractive approach to analyze large-scale pharmacogenetic SNP data because of their ability to automatically learn complex models that can be used for the prediction and discovery of novel biological hypotheses.
asthma; Bayesian networks; β2-agonists; bronchodilator response; prediction
Although females suffer twice as much as males from stress-related disorders, sex-specific participating and pathogenic cellular stress mechanisms remain uncharacterized. Using corticotropin-releasing factor receptor 2–deficient (Crhr2−/− ) and wild-type (WT) mice, we show that CRF receptor type 2 (CRF2) and its high-affinity ligand, urocortin 1 (Ucn1), are key mediators of the endoplasmic reticulum (ER) stress response in a murine model of acute pancreatic inflammation. Ucn1 was expressed de novo in acinar cells of male, but not female WT mice during acute inflammation. Upon insult, acinar Ucn1 induction was markedly attenuated in male but not female Crhr2−/− mice. Crhr2−/− mice of both sexes show exacerbated acinar cell inflammation and necrosis. Electron microscopy showed mild ER damage in WT male mice and markedly distorted ER structure in Crhr2−/− male mice during pancreatitis. WT and Crhr2−/− female mice showed similarly distorted ER ultrastructure that was less severe than distortion seen in Crhr2−/− male mice. Damage in ER structure was accompanied by increased ubiquitination, peIF2, and mistargeted localization of vimentin in WT mice that was further exacerbated in Crhr2−/− mice of both sexes during pancreatitis. Exogenous Ucn1 rescued many aspects of histological damage and cellular stress response, including restoration of ER structure in male WT and Crhr2−/−mice, but not in females. Instead, females often showed increased damage. Thus, specific cellular pathways involved in coping and resolution seem to be distinct to each sex. Our results demonstrate the importance of identifying sex-specific pathogenic mechanisms and their value in designing effective therapeutics.
Rationale: Improvement in FEV1 is a main endpoint in clinical trials assessing the efficacy of bronchodilators. However, the effect of bronchodilators on maximal expiratory flow may be confounded by thoracic gas compression (TGC).
Objective: To determine whether TGC confounds effect of albuterol on FEV1.
Methods: We evaluated the response to albuterol inhalation in 10 healthy subjects, 9 subjects with asthma, and 15 subjects with chronic obstructive pulmonary disease (COPD) with mean (SD) age in years of 38 (SD, 11), 45 (SD, 11), and 64 (SD, 8), respectively. Lung mechanics were measured at baseline and 20 minutes after inhalation of 180 μg of albuterol. We then applied a novel method to calculate FEV1 corrected for the effect of TGC (NFEV1).
Results: Prior to albuterol administration, NFEV1 was significantly higher than FEV1. However, post–albuterol inhalation, FEV1 increased more than NFEV1 because of reduced TGC. In multiple regression analysis, the changes in TGC, inspiratory lung resistance, and ratio of residual volume to total lung capacity postalbuterol predicted more than 75% of FEV1 improvement in patients with COPD.
Conclusion: Improvements in FEV1 after albuterol in patients with COPD are due to reduction of lung resistance, hyperinflation, and TGC. The latter is negligible during tidal breathing. Thus, although reduction of lung resistance and hyperinflation may result in improved dyspnea with a bronchodilator, the contribution of TGC reduction to improvement of FEV1 may not exert any meaningful clinical effect during tidal breathing. This fact has to be taken into consideration when assessing the efficacy of new bronchodilators.
FEV1; chronic obstructive pulmonary disease; asthma; lung mechanics; albuterol
Stress-induced affective disorders, such as depression and anxiety, are more prevalent in females than in males. The reduced vulnerability to these disorders in males may be due to the presence of androgens, which are known to dampen the stress response and reduce anxiety-like behaviors. However, a neurobiological mechanism for this sex difference has yet to be elucidated. Corticotropin-releasing hormone receptor 2 (CRHR2) has been implicated in regulating anxiety-type behaviors and is expressed in stress-responsive brain regions that also contain androgen receptors (AR). We hypothesized that androgen may exert its effects through actions on CRHR2 and we therefore examined the regulation of CRHR2 mRNA and receptor binding in the male rat forebrain following androgen administration. Young adult male Sprague/Dawley rats were gonadectomized (GDX) and treated with the non-aromatizable androgen, dihydrotestosterone propionate (DHTP) using hormone filled Silastic capsules. Control animals received empty capsules. Using quantitative real time RT-PCR, CRHR2 mRNA levels were determined in block dissected brain regions. DHTP treatment significantly increased CRHR2 mRNA expression in the hippocampus, hypothalamus, and lateral septum (p < 0.01) when compared to vehicle-treated controls. A similar trend was observed in amygdala (p = 0.05). Furthermore, in vitro autoradiography revealed significantly higher CRHR2 binding in the lateral septum in androgen-treated males, with the highest difference observed in the ventral lateral region. Regulation of CRHR2 mRNA by AR was also examined using an in vitro approach. Hippocampal neurons, which contain high levels of AR, were harvested from E17–18 rat fetuses, and maintained in primary culture for 14 days. Neurons were then treated with dihydrotestosterone (DHT; 1 nM), DHT plus flutamide (an androgen receptor antagonist), or vehicle for 48 hours. CRHR2 mRNA levels were measured using quantitative real time RT-PCR. Consistent with in vivo studies, DHT significantly increased CRHR2 mRNA expression in hippocampal neurons (p<.02) compared to vehicle treated controls. Flutamide treatment prevented the effect of DHT on CRHR2 mRNA indicating that DHT’s effect on CRHR2 expression is AR-mediated. Thus, the CRHR2 gene appears to be a target for regulation by AR and these data suggest a potential mechanism by which androgen may alter mood and anxiety-related behaviors.
Stress; Anxiety; Gonadal Steroids; HPA Axis; Androgen; CRH
Stress is a general risk factor for psychopathology but the mechanisms underlying this relationship remain largely unknown. Animal studies and limited human research suggest that stress can induce anhedonic behavior. Moreover, emerging data indicate that genetic variation within the corticotropin-releasing hormone type 1 receptor gene (CRHR1) at rs12938031 may promote psychopathology, particularly in the context of stress. Using an intermediate phenotypic neurogenetics approach, we assessed how stress and CRHR1 genetic variation (rs12938031) influence reward learning, an important component of anhedonia. Psychiatrically healthy female participants (n = 75) completed a probabilistic reward learning task during stress and no-stress conditions while 128-channel event-related potentials were recorded. Fifty-six participants were also genotyped across CRHR1. Response bias, an individual’s ability to modulate behavior as a function of reward, was the primary behavioral variable of interest. The feedback-related positivity (FRP) in response to reward feedback was used as a neural index of reward learning. Relative to the no-stress condition, acute stress was associated with blunted response bias as well as a smaller and delayed FRP (indicative of disrupted reward learning) and reduced anterior cingulate and orbitofrontal cortex activation to reward. Critically, rs12938031 interacted with stress to influence reward learning: both behaviorally and neurally, A homozygotes showed stress-induced reward learning abnormalities. These findings indicate that acute, uncontrollable stressors reduce participants’ ability to modulate behavior as a function of reward, and that such effects are modulated by CRHR1 genotype. Homozygosity for the A allele at rs12938031 may increase risk for psychopathology via stress-induced reward learning deficits.
An important etiological hypothesis about depression is stress has neurotoxic effects that damage the hippocampal cells. Corticotropin-releasing hormone (CRH) regulates brain-derived neurotrophic factor (BDNF) expression through influencing cAMP and Ca2+ signaling pathways during the course. The aim of this study is to examine the single and combined effects of CRH receptor 1 (CRHR1) and BDNF genes in recurrent major depressive disorder (MDD).
The sample consists of 181 patients with recurrent MDD and 186 healthy controls. Whether genetic variations interaction between CRHR1 and BDNF genes might be associated with increased susceptibility to recurrent MDD was studied by using a gene-based association analysis of single-nucleotide polymorphisms (SNPs). CRHR1 gene (rs1876828, rs242939 and rs242941) and BDNF gene (rs6265) were identified in the samples of patients diagnosed with recurrent MDD and matched controls. Allelic association between CRHR1 rs242939 and recurrent MDD was found in our sample (allelic: p = 0.018, genotypic: p = 0.022) with an Odds Ratio 0.454 (95% CI 0.266–0.775). A global test of these four haplotypes showed a significant difference between recurrent MDD group and control group (chi-2 = 13.117, df = 3, P = 0.016. Furthermore, BDNF and CRHR1 interactions were found in the significant 2-locus, gene–gene interaction models (p = 0.05) using a generalized multifactor dimensionality reduction (GMDR) method.
Our results suggest that an interaction between CRHR1 and BDNF genes constitutes susceptibility to recurrent MDD.
Gene x environment (GxE) interactions mediating depressive symptoms have been separately identified in the stress-sensitive serotonergic (5-HTTLPR) and corticotropin-releasing hormone (CRHR1) systems. Our objective was to examine whether the effects of child abuse are moderated by gene x gene (GxG) interactions between CRHR1 and 5-HTTLPR polymorphisms.
We used an association study examining GxGxE interactions of CRHR1 and 5-HTTLPR polymorphisms and measures of child abuse on adult depressive symptomatology. The participant population (N=1392) was African-American, of low socioeconomic status (60% with <$1000/month family income), and with high rates of childhood and lifetime trauma. Depressive symptoms were measured with Beck Depression Inventory (BDI) and history of Major Depression by Structure Clinical Interview based on DSM-IV (SCID).
We first replicated an interaction of child abuse and 5-HTTLPR on lifetime SCID diagnosis of major depression in a subsample (N= 236) of the study population – the largest African American 5-HTTLPR cohort reported to date. We then extended our previously reported interaction with both a CRHR1 SNP (rs110402) and TCA haplotype interacting with child abuse to predict current symptoms (N=1059; p = 0.0089). We found that the 5-HTTLPR S allele interacted with CRHR1 haplotypes and child abuse to predict current depressive symptoms (N = 856, p = 0.016).
These data suggest that GxE interactions predictive of depressive symptoms may be differentially sensitive to levels of childhood trauma, and the effects of child abuse are moderated by genetic variation at both the CRHR1 and 5-HTTLPR loci and by their GxG interaction.
Child Abuse; Childhood Maltreatmet; Trauma; Depression; PTSD; Genetic; risk factor
Background: Lactic acidosis is a recognised event in adult patients with status asthmaticus, particularly in the setting of intensive care. However, it has been infrequently studied in patients attending the emergency departments (ED).
Methods: We conducted a prospective and descriptive study to assess levels of lactate and effects on bronchodilator response in adult patients with acute severe asthma treated with high doses of albuterol in the ED. In total, 18 subjects (mean (SD) age 42.9 (2.7) years, FEV1 = 32.2 (10.9)% of predicted) who presented to an emergency department were enrolled in the study. All patients were treated with albuterol; four puffs (100 µg/puff) at 10 minute intervals, delivered by a pressurised metered dose inhaler into a spacer device over a 2 hour period.
Results: At the end of treatment, mean (SD) plasma lactate level (2.94 (2.1) mmol/l) was significantly higher (p = 0.001) than baseline. Of the 18 patients, nine (50%) showed lactate levels ⩾2.5 mmol/l (four patients presented values >4 mmol/l); these patients had a shorter duration of attack prior to ED presentation (p = 0.01), a higher pretreatment heart rate (p = 0.005), a lower pretreatment SpO2 (p = 0.03), a lower pretreatment PO2 (p = 0.009), a higher pretreatment PCO2, and a lower pretreatment serum potassium (p = 0.005). However, there were no significant differences in the airway response between groups.
Conclusions: This study confirmed previous observations that high lactate concentrations can develop during the first hours of inhaled beta agonist treatment. The presence of a previous hyperadrenergic state may predispose to the development of this condition. A significant improvement in lung function was associated with elevated lactate levels.