Association of corticotropin-releasing hormone receptor-2 genetic variants with acute bronchodilator response in asthma

Circulating microRNAs associated with bronchodilator response in childhood asthma

BACKGROUND

Bronchodilator response (BDR) is a measure of improvement in airway smooth muscle tone, inhibition of liquid accumulation and mucus section into the lumen in response to short-acting beta-2 agonists that varies among asthmatic patients. MicroRNAs (miRNAs) are well-known post-translational regulators. Identifying miRNAs associated with BDR could lead to a better understanding of the underlying complex pathophysiology.

OBJECTIVE

The purpose of this study is to identify circulating miRNAs associated with bronchodilator response in asthma and decipher possible mechanism of bronchodilator response variation.

METHODS

We used available small RNA sequencing on blood serum from 1,134 asthmatic children aged 6 to 14 years who participated in the Genetics of Asthma in Costa Rica Study (GACRS). We filtered the participants into the highest and lowest bronchodilator response (BDR) quartiles and used DeSeq2 to identify miRNAs with differential expression (DE) in high (N = 277) vs. low (N = 278) BDR group. Replication was carried out in the Leukotriene modifier Or Corticosteroids or Corticosteroid-Salmeterol trial (LOCCS), an adult asthma cohort. The putative target genes of DE miRNAs were identified, and pathway enrichment analysis was performed.

RESULTS

We identified 10 down-regulated miRNAs having odds ratios (OR) between 0.37 and 0.76 for a doubling of miRNA counts and one up-regulated miRNA (OR = 2.26) between high and low BDR group. These were assessed for replication in the LOCCS cohort, where two miRNAs (miR-200b-3p and miR-1246) were associated. Further, functional annotation of 11 DE miRNAs were performed as well as of two replicated miRs. Target genes of these miRs were enriched in regulation of cholesterol biosynthesis by SREBPs, ESR-mediated signaling, G1/S transition, RHO GTPase cycle, and signaling by TGFB family pathways.

CONCLUSION

MiRNAs miR-1246 and miR-200b-3p are associated with both childhood and adult asthma BDR. Our findings add to the growing body of evidence that miRNAs play a significant role in the difference of asthma treatment response among patients as it points to genomic regulatory machinery underlying difference in bronchodilator response among patients.

TRIAL REGISTRATION

LOCCS cohort [ClinicalTrials.gov number NCT00156819, Registration date 20050912], GACRS cohort [ClinicalTrials.gov number NCT00021840].

Circulating MicroRNAs associated with Bronchodilator Response in Childhood Asthma

Rationale

Bronchodilator response (BDR) is a measure of improvement in airway smooth muscle tone, inhibition of liquid accumulation and mucus section into the lumen in response to short-acting beta-2 agonists that varies among asthmatic patients. MicroRNAs (miRNAs) are well-known post-translational regulators. Identifying miRNAs associated with BDR could lead to a better understanding of the underlying complex pathophysiology.

Objective

The purpose of this study is to identify circulating miRNAs associated with bronchodilator response in asthma and decipher possible mechanism of bronchodilator response variation.

Methods

We used available small RNA sequencing on blood serum from 1,134 asthmatic children aged 6 to 14 years who participated in the Genetics of Asthma in Costa Rica Study (GACRS). We filtered the participants into high and low bronchodilator response (BDR) quartiles and used DeSeq2 to identify miRNAs with differential expression (DE) in high (N= 277) vs low (N= 278) BDR group. Replication was carried out in the Leukotriene modifier Or Corticosteroids or Corticosteroid-Salmeterol trial (LOCCS), an adult asthma cohort. The putative target genes of DE miRNAs were identified, and pathway enrichment analysis was performed.

Results

We identified 10 down-regulated miRNAs having odds ratios (OR) between 0.37 and 0.76 for a doubling of miRNA counts and one up-regulated miRNA (OR=2.26) between high and low BDR group. These were assessed for replication in the LOCCS cohort, where two miRNAs (miR-200b-3p and miR-1246) were associated. Further, functional annotation of 11 DE miRNAs were performed as well as of two replicated miRs. Target genes of these miRs were enriched in regulation of cholesterol biosynthesis by SREBPs, ESR-mediated signaling, G1/S transition, RHO GTPase cycle, and signaling by TGFB family pathways.

Conclusion

MiRNAs miR-1246 and miR-200b-3p are associated with both childhood and adult asthma BDR. Our findings add to the growing body of evidence that miRNAs play a significant role in the difference of asthma treatment response among patients as it points to genomic regulatory machinery underlying difference in bronchodilator response among patients.

Trial registration

LOCCS cohort [ClinicalTrials.gov number: NCT00156819], GACRS cohort [ClinicalTrials.gov number: NCT00021840].

The impact of genomic variants on patient response to inhaled bronchodilators: a comprehensive update

INTRODUCTION

The bronchodilator response (BDR) depends on many factors, including genetic ones. Numerous single nucleotide polymorphisms (SNPs) influencing BDR have been identified. However, despite several studies in this field, genetic variations are not currently being utilized to support the use of bronchodilators.

AREAS COVERED

In this narrative review, the possible impact of genetic variants on BDR is discussed.

EXPERT OPINION

Pharmacogenetic studies of β₂-agonists have mainly focused on ADRB2 gene. Three SNPs, A46G, C79G, and C491T, have functional significance. However, other uncommon variants may contribute to individual variability in salbutamol response. SNPs haplotypes in ADRB2 may have a role. Many variants in genes coding for muscarinic ACh receptor (mAChR) have been reported, particularly in the M₂ and, to a lesser degree, M₃ mAChRs, but no consistent evidence for a pharmacological relevance of these SNPs has been reported. Moreover, there is a link between SNPs and ethnic and/or age profiles regarding BDR. Nevertheless, replication of pharmacogenetic results is limited and often, BDR is dissociated from what is expected based on SNP identification. Pharmacogenetic studies on bronchodilators must continue. However, they must integrate data derived from a multi-omics approach with epigenetic factors that may modify BDR.

The Genetic Factors of the Airway Epithelium Associated with the Pathology of Asthma

Asthma is a chronic disease of the airways characterized by inflammation, tightened muscles, and thickened airway walls leading to symptoms such as shortness of breath, chest tightness, and cough in patients. The increased risk of asthma in children of asthmatics parents supports the existence of genetic factors involved in the pathogenesis of this disease. Genome-wide association studies have discovered several single nucleotide polymorphisms associated with asthma. These polymorphisms occur within several genes and can contribute to different asthma phenotypes, affect disease severity, and clinical response to different therapies. The complexity in the etiology of asthma also results from interactions between environmental and genetic factors. Environmental exposures have been shown to increase the prevalence of asthma in individuals who are genetically susceptible. This review summarizes what is currently known about the genetics of asthma in relation to risk, response to common treatments, and gene-environmental interactions.

Genome-wide association study in minority children with asthma implicates DNAH5 in bronchodilator responsiveness

Variability in response to short-acting β2-agonists (e.g., albuterol) among patients with asthma from diverse racial/ethnic groups may contribute to asthma disparities. We sought to identify genetic variants associated with bronchodilator response (BDR) to identify potential mechanisms of drug response and risk factors for worse asthma outcomes. Genome-wide association studies of bronchodilator response (BDR) were performed using TOPMed Whole Genome Sequencing data of the Asthma Translational Genomic Collaboration (ATGC), which corresponded to 1136 Puerto Rican, 656 Mexican and 4337 African American patients with asthma. With the population-specific GWAS results, a trans-ethnic meta-analysis was performed to identify BDR-associated variants shared across the three populations. Replication analysis was carried out in three pediatric asthma cohorts, including CAMP (Childhood Asthma Management Program; n = 560), GACRS (Genetics of Asthma in Costa Rica Study; n = 967) and HPR (Hartford-Puerto Rico; n = 417). A genome-wide significant locus (rs35661809; P = 3.61 × 10-8) in LINC02220, a non-coding RNA gene, was identified in Puerto Ricans. While this region was devoid of protein-coding genes, capture Hi-C data showed a distal interaction with the promoter of the DNAH5 gene in lung tissue. In replication analysis, the GACRS cohort yielded a nominal association (1-tailed P < 0.05). No genetic variant was associated with BDR at the genome-wide significant threshold in Mexicans and African Americans. Our findings help inform genetic underpinnings of BDR for understudied minority patients with asthma, but the limited availability of genetic data for racial/ethnic minority children with asthma remains a paramount challenge.

A genome-wide association study of bronchodilator response in participants of European and African ancestry from six independent cohorts

Introduction

Bronchodilator response (BDR) is a measurement of acute bronchodilation in response to short-acting β2-agonists, with a heritability between 10 and 40%. Identifying genetic variants associated with BDR may lead to a better understanding of its complex pathophysiology.

Methods

We performed a genome-wide association study (GWAS) of BDR in six adult cohorts with participants of European ancestry (EA) and African ancestry (AA) including community cohorts and cohorts ascertained on the basis of obstructive pulmonary disease. Validation analysis was carried out in two paediatric asthma cohorts.

Results

A total of 10 623 EA and 3597 AA participants were included in the analyses. No single nucleotide polymorphism (SNP) was associated with BDR at the conventional genome-wide significance threshold (p<5×10-8). Performing fine mapping and using a threshold of p<5×10-6 to identify suggestive variants of interest, we identified three SNPs with possible biological relevance: rs35870000 (within FREM1), which may be involved in IgE- and IL5-induced changes in airway smooth muscle cell responsiveness; rs10426116 (within ZNF284), a zinc finger protein, which has been implicated in asthma and BDR previously; and rs4782614 (near ATP2C2), involved in calcium transmembrane transport. Validation in paediatric cohorts yielded no significant SNPs, possibly due to age-genotype interaction effects.

Conclusion

Ancestry-stratified and ancestry-combined GWAS meta-analyses of over 14 000 participants did not identify genetic variants associated with BDR at the genome-wide significance threshold, although a less stringent threshold identified three variants showing suggestive evidence of association. A common definition and protocol for measuring BDR in research may improve future efforts to identify variants associated with BDR.

Pharmacogenomics and Pediatric Asthmatic Medications

Asthma is a respiratory condition often stemming from childhood, characterized by difficulty breathing and/or chest tightness. Current treatment options for both adults and children include beta-2 agonists, inhaled corticosteroids (ICS), and leukotriene modifiers (LTM). Despite recommendations by the Global Initiative for Asthma, a substantial number of patients are unresponsive to treatment and unable to control symptoms. Pharmacogenomics have increasingly become the front line of precision medicine, especially with the recent use of candidate gene and genome- wide association studies (GWAS). Screening patients preemptively could likely decrease adverse events and therapeutic failure. However, research in asthma, specifically in pediatrics, has been low. Although numerous adult trials have evaluated the impact of pharmacogenomics and treatment response, the lack of evidence in children has hindered progress towards clinical application. This review aims to discuss the impact of genetic variability and response to asthmatic medications in the pediatric population.

Association between genetic variant rs2267716 of CRHR2 gene with colorectal cancer

Colorectal cancer (CRC) is the third most common cancer and one of the main causes of death around the world. Multiple lines of evidence have suggested the role of the corticotropin-releasing hormone (CRH) family in CRC induction, including the low expression of corticotropin-releasing hormone receptor 2 (CRHR2), which is an angiogenesis inhibitor and inflammatory modulator. Previous research suggests that CRHR2 expression in colonic intestinal cells can regulate migration, proliferation and apoptosis through the modulation of several pathways. The aim of this study was to analyze the association of the rs10250835, rs2267716 and rs2267717 variants of CRHR2 gene with CRC in the Mexican population in order to consider its predictive value in CRC. This cross-sectional study included a group of 187 unrelated patients with sporadic CRC and a control group of 191 healthy blood donors. DNA extraction from peripheral blood was carried out using the Miller method. Identification of the rs10250835 variant was performed using PCR-restriction fragment length polymorphism (RFLP) and the rs2267716 and rs2267717 variants using TaqMan allelic discrimination assay. The minor allele homozygous CC of the rs2267716 variant of CRHR2 showed significant difference between CRC and control group (p=0.025), as well as the GCA haplotype (p=0.007), corresponding to the rs10250835, rs2267716 and rs2267717 variants, respectively. Our results suggest that the rs2267716 variant and GCA haplotype of CRHR2 represent a risk factor for CRC development in Mexican patients.

The role of polymorphic variants of arginase genes (ARG1, ARG2) involved in beta-2-agonist metabolism in the development and course of asthma

Asthma is a common severe disease of the respiratory tract, it leads to a significant impairment in the quality of a patient’s life unless effectively treated. Uncontrolled asthma symptoms are a cause of disease progression and development, they lead to an increase in the patient’s disability. The sensitivity to asthma therapy largely depends on the interaction of genetic and epigenetic factors, which account for about 50–60 % of variability of therapeutic response. Beta-2-agonists are some of the major class of bronchodilators used for asthma management. According to published data, allelic variants of the arginase ARG1 and ARG2 genes are associated with a risk of asthma development, spirometry measures and efficacy of bronchodilator therapy. High arginase activity results in a low level of plasma L-arginine and in a decrease in nitric oxide, and, as a result, in an increase in airway inflammation and remodeling. Arginase genetic polymorphisms (rs2781667 of the ARG1 gene, rs17249437, rs3742879, rs7140310 of the ARG2 gene) were studied in 236 children with asthma and 194 unrelated healthy individuals of Russian, Tatar and Bashkir ethnicity from the Republic of Bashkortostan. Association analysis of the studied polymorphisms with asthma development and course, the sensitivity to therapy in patients was carried out. It was found that the rs2781667*C allele of the ARG1 gene is a marker of an increased risk of asthma in Tatars. In Russians, the association of rs17249437*TT and rs3742879*GG genotypes of the ARG2 gene with a decrease in spirometry measures (FEV1, MEF25) was established. In Russians and Tatars receiving glucocorticoid monotherapy or combination therapy, the association of the rs17249437*T allele and rs17249437*TT genotype of the ARG2 gene with a partially controlled and uncontrolled course of asthma was shown.

Pharmacologic Management of Severe Bronchopulmonary Dysplasia

Few medications are available and well tested to treat infants who already have developed or inevitably will develop severe bronchopulmonary dysplasia (sBPD). Infants who develop sBPD clearly have not benefited from decades of research efforts to identify clinically meaningful preventive therapies for very preterm infants in the first days and weeks of their postnatal lives. This review addresses challenges to individualized approaches to medication use for sBPD. Specific challenges include understanding the combination of an individual infant's postmenstrual and postnatal age and the developmental status of drug-metabolizing enzymes and receptor expression. This review will also explore the reasons for the variable responsiveness of infants to specific therapies, based on current understanding of developmental pharmacology and pharmacogenetics. Data demonstrating the remarkable variability in the use of commonly prescribed drugs for sBPD are presented, and a discussion about the current use of some of these medications is provided. Finally, the potential use of antifibrotic medications in late-stage sBPD, which is characterized by a profibrotic state, is addressed.

Applying whole-genome sequencing in relation to phenotype and outcomes in siblings with cystic fibrosis

Variations in disease onset and/or severity have often been observed in siblings with cystic fibrosis (CF), despite the same CFTR genotype and environment. We postulated that genomic variation (modifier and/or pharmacogenomic variants) might explain these clinical discordances. From a cohort of patients included in the Wisconsin randomized clinical trial (RCT) of newborn screening (NBS) for CF, we identified two brothers who showed discordant lung disease courses as children, with one milder and the other more severe than average, and a third, eldest brother, who also has severe lung disease. Leukocytes were harvested as the source of DNA, and whole-genome sequencing (WGS) was performed. Variants were identified and analyzed using in-house-developed informatics tools. Lung disease onset and severity were quantitatively different between brothers during childhood. The youngest, less severely affected brother is homozygous for HFE p.H63D. He also has a very rare PLG p.D238N variant that may influence host-pathogen interaction during chronic lung infection. Other variants of interest were found differentially between the siblings. Pharmacogenomics findings were consistent with the middle, most severely affected brother having poor outcomes to common CF treatments. We conclude that genomic variation between siblings with CF is expected. Variable lung disease severity may be associated with differences acting as genetic modifiers and/or pharmacogenomic factors, but large cohort studies are needed to assess this hypothesis.

Pharmacogenetic Factors Affecting Asthma Treatment Response. Potential Implications for Drug Therapy

Asthma is a frequent disease, mainly characterized by airway inflammation, in which drug therapy is crucial in its management. The potential of pharmacogenomics testing in asthma therapy has been, to date, little explored. In this review, we discuss pharmacogenetic factors affecting asthma treatment, both related to drugs used as controller medications for regular maintenance, such as inhaled corticosteroids, anti-leukotriene agents, long-acting beta-agonists, and the new biologic agents used to treat severe persistent asthma. In addition, we discuss current pharmacogenomics knowledge for rescue medications provided to all patients for as-needed relief, such as short-acting beta-agonists. Evidence for genetic variations as a factor related to drugs response has been provided for the following genes and groups of drugs: Inhaled corticosteroids: FCER2; anti-leukotriene agents: ABCC1, and LTC4S; beta-agonists: ADRB2. However, the following genes require further studies confirming or rejecting association with the response to asthma therapy: ADCY9, ALOX5, ARG1, ARG2, CRHR1, CRHR2, CYP3A4, CYP3A5, CYSLTR1, CYSLTR2, GLCCI1, IL4RA, LTA4H, ORMDL3, SLCO2B1, SPATS2L, STIP1, T, TBX21, THRA, THRB, and VEGFA. Although only a minority of these genes are, at present, listed as associated with drugs used in asthma therapy, in the Clinical Pharmacogenomics Implementation Consortium gene-drug pair list, this review reveals that sufficient evidence to start testing the potential of clinical pharmacogenomics in asthma therapy already exists. This evidence supports the inclusion in pilot pharmacogenetics tests of at least four genes. Hopefully these tests, if proven useful, will increase the efficiency and the safety of asthma therapy.

A genome-wide association and admixture mapping study of bronchodilator drug response in African Americans with asthma

Short-acting β₂-adrenergic receptor agonists (SABAs) are the most commonly prescribed asthma medications worldwide. Response to SABAs is measured as bronchodilator drug response (BDR), which varies among racial/ethnic groups in the U.S^{1, 2}. However, the genetic variation that contributes to BDR is largely undefined in African Americans with asthma³. To identify genetic variants that may contribute to differences in BDR in African Americans with asthma, we performed a genome-wide association study (GWAS) of BDR in 949 African American children with asthma, genotyped with the Axiom World Array 4 (Affymetrix, Santa Clara, CA) followed by imputation using 1000 Genomes phase III genotypes. We used linear regression models adjusting for age, sex, body mass index (BMI) and genetic ancestry to test for an association between BDR and genotype at single nucleotide polymorphisms (SNPs). To increase power and distinguish between shared vs. population-specific associations with BDR in children with asthma, we performed a meta-analysis across 949 African Americans and 1,830 Latinos (Total=2,779). Lastly, we performed genome-wide admixture mapping to identify regions whereby local African or European ancestry is associated with BDR in African Americans. We identified a population-specific association with an intergenic SNP on chromosome 9q21 that was significantly associated with BDR (rs73650726, p=7.69×10⁻⁹). A trans-ethnic meta-analysis across African Americans and Latinos identified three additional SNPs within the intron of PRKG1 that were significantly associated with BDR (rs7903366, rs7070958, and rs7081864, p≤5×10⁻⁸). Our results failed to replicate in three additional populations of 416 Latinos and 1,615 African Americans. Our findings indicate that both population specific and shared genetic variation contributes to differences in BDR in minority children with asthma, and that the genetic underpinnings of BDR may differ between racial/ethnic groups.

Pharmacogenetics of asthma: toward precision medicine

PURPOSE OF REVIEW

Although currently available drugs to treat asthma are effective in most patients, a proportion of patients do not respond or experience side-effects; which is partly genetically determined. Pharmacogenetics is the study of how genetic variations influence drug response. In this review, we summarize prior results and recent studies in pharmacogenetics to determine if we can use genetic profiles for personalized treatment of asthma.

RECENT FINDINGS

The field of pharmacogenetics has moved from candidate gene studies in single populations toward genome-wide association studies and meta-analysis of multiple studies. New technologies have been used to enrich results, and an expanding number of genetic loci have been associated with therapeutic responses to asthma drugs. Prospective, genotype-stratified treatment studies have been conducted for β2-agonists, showing attenuated response in children carrying the Arg16 variant in the β2-adrenoreceptor gene.

SUMMARY

Although there has been much progress, many findings have not been replicated and currently known genetic loci only account for a fraction of variability in drug response. More research is necessary to translate into clinical practice. A polygenic predictive approach integrated in complex networks with other 'omics' technologies could aid to achieve this goal. Finally, to change clinical practice, studies that compare precision medicine with traditional medicine are needed.

Pharmacogenetic and pharmacogenomic considerations of asthma treatment

INTRODUCTION

Pharmacogenetic and pharmacogenomic approaches are already utilized in some areas, such as oncology and cardiovascular disease, for selecting appropriate patients and/or establishing treatment and dosing guidelines. This is not true in asthma although many patients have different responses to drug treatment due to genetic factors. Areas covered: Several genetic factors that affect the pharmacotherapeutic responses to asthma medications, such as β₂-AR agonists, corticosteroids, and leukotriene modifiers and could contribute to significant between-person variability in response are described. Expert opinion: An expanding number of genetic loci have been associated with therapeutic responses to asthma drugs but the individual effect of one single-nucleotide polymorphism is partial. In fact, epigenetic changes can modify genetic effects in time-, environment-, and tissue-specific manners, genes interact together in networks, and nongenetic components such as environmental exposures, gender, nutrients, and lifestyle can significantly interact with genetics to determine the response to therapy. Therefore, well-designed randomized controlled trials or observational studies are now mandatory to define if response to asthma medications in individual patients can be improved by using pharmacogenetic predictors of treatment response. Meanwhile, routine implementation of pharmacogenetics and pharmacogenomics into clinical practice remains a futuristic, far-off challenge for many clinical practices.

Single-nucleotide polymorphisms in genes related to the hypothalamic-pituitary-adrenal axis as risk factors for posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is a common psychiatric disorder. The etiology of PTSD is multifactorial, depending on many environmental and genetic risk factors, and the exposure to life or physical integrity-threatening events. Several studies have shown significant correlations of many neurobiological findings with PTSD. Hypothalamic-pituitary-adrenal (HPA) axis dysfunction is strongly correlated with this disorder. One hypothesis is that HPA axis dysfunction may precede the traumatic event, suggesting that genes expressed in the HPA axis may be involved in the development of PTSD. This article reviews molecular genetic studies related to PTSD collected through a literature search performed in PubMed, MEDLINE, ScienceDirect, and Scientific Electronic Library Online (SciELO). The results of these studies suggest that several polymorphisms in the HPA axis genes, including FKBP5, NR3C1, CRHR1, and CRHR2, may be risk factors for PTSD development or may be associated with the severity of PTSD symptoms.

Association between obesity and asthma - epidemiology, pathophysiology and clinical profile

Obesity is a risk factor for asthma, and obese asthmatics have lower disease control and increased symptom severity. Several putative links have been proposed, including genetics, mechanical restriction of the chest and the intake of corticosteroids. The most consistent evidence, however, comes from studies of cytokines produced by the adipose tissue called adipokines. Adipokine imbalance is associated with both proinflammatory status and asthma. Although reverse causation has been proposed, it is now acknowledged that obesity precedes asthma symptoms. Nevertheless, prenatal origins of both conditions complicate the search for causality. There is a confirmed role of neuro-immune cross-talk mediating obesity-induced asthma, with leptin playing a key role in these processes. Obesity-induced asthma is now considered a distinct asthma phenotype. In fact, it is one of the most important determinants of asthma phenotypes. Two main subphenotypes have been distinguished. The first phenotype, which affects adult women, is characterised by later onset and is more likely to be non-atopic. The childhood obesity-induced asthma phenotype is characterised by primary and predominantly atopic asthma. In obesity-induced asthma, the immune responses are shifted towards T helper (Th) 1 polarisation rather than the typical atopic Th2 immunological profile. Moreover, obese asthmatics might respond differently to environmental triggers. The high cost of treatment of obesity-related asthma, and the burden it causes for the patients and their families call for urgent intervention. Phenotype-specific approaches seem to be crucial for the success of prevention and treatment.

[Research advances in gene polymorphisms in biological pathways of drugs for asthma]

The studies on gene polymorphisms in biological pathways of the drugs for the treatment of asthma refer to the studies in which pharmacogenetic methods, such as genome-wide association studies, candidate gene studies, genome sequencing, admixture mapping analysis, and linkage disequilibrium, are used to identify, determine, and repeatedly validate the effect of one or more single nucleotide polymorphisms on the efficacy of drugs. This can provide therapeutic strategies with optimal benefits, least side effects, and lowest costs to patients with asthma, and thus realize individualized medicine. The common drugs for asthma are β2 receptor agonists, glucocorticoids, and leukotriene modifiers. This article reviews the research achievements in polymorphisms in biological pathways of the common drugs for asthma, hoping to provide guidance for pharmacogenetic studies on asthma in future and realize individualized medicine for patients with asthma soon.

Corticotropin-Releasing Hormone Receptor 2 Gene Variants in Irritable Bowel Syndrome

Background

Corticotropin-releasing hormone (CRH) plays an important role in the pathophysiology of irritable bowel syndrome (IBS) and regulates the stress response through two CRH receptors (R1 and R2). Previously, we reported that a CRHR1 gene polymorphism (rs110402, rs242924, and rs7209436) and haplotypes were associated with IBS. However, the association between the CRHR2 gene and IBS was not investigated. We tested the hypothesis that genetic polymorphisms and haplotypes of CRHR2 are associated with IBS pathophysiology and negative emotion in IBS patients.

Methods

A total of 142 IBS patients and 142 healthy controls participated in this study. Seven single nucleotide polymorphisms (SNPs) of the CRHR2 gene (rs4722999, rs3779250, rs2240403, rs2267710, rs2190242, rs2284217, and rs2284220) were genotyped. Subjects' psychological states were evaluated using the Perceived-Stress Scale, the State-Trait Anxiety Inventory, and the Self-Rating Depression Scale.

Results

We found that rs4722999 and rs3779250, located in intronic region, were associated with IBS in terms of genotype frequency (rs4722999: P = 0.037; rs3779250: P = 0.017) and that the distribution of the major allele was significantly different between patients and controls. There was a significant group effect (controls vs. IBS), and a CRHR2 genotype effect was observed for three psychological scores, but the interaction was not significant. We found a haplotype of four SNPs (rs4722999, rs3779250, rs2240403, and rs2267710) and two SNPs (rs2284217 and rs2284220) in strong linkage disequilibrium (D′ > 0.90). We also found that haplotypes of the CRHR2 gene were significantly different between IBS patients and controls and that they were associated with negative emotion.

Conclusion

Our findings support the hypothesis that genetic polymorphisms and haplotypes of CRHR2 are related to IBS. In addition, we found associations between CRHR2 genotypes and haplotypes and negative emotion in IBS patients and controls. Further studies on IBS and the CRH system are warranted.

Pharmacogenomic test that predicts response to β2-agonists in adults with asthma is cost effective

BACKGROUND

Pharmacogenomic tests that predict which asthma patients are likely to respond to β₂-agonists hold promise to improve care for asthma.

OBJECTIVE

To identify the clinical and economic circumstances under which a pharmacogenomic test that predicts response to β₂-agonists might or might not be an appropriate, cost-effective option.

METHODS

We synthesized published data on clinical and economic outcomes in adults 18-35 to project 10-year costs, quality-adjusted life years and cost-effectiveness of pharmacogenomic testing for β₂-agonist response.

RESULTS

Pharmacogenomic testing for β₂-agonist response conferred a cost-effectiveness ratio of $13,700 per quality-adjusted life year gained compared with no testing.

CONCLUSION

Pharmacogenomic testing for β₂-agonist response in individuals with asthma is potentially cost effective and should be pursued by test developers.

Genome-wide association study of short-acting β2-agonists. A novel genome-wide significant locus on chromosome 2 near ASB3

RATIONALE

β2-Agonists are the most common form of treatment of asthma, but there is significant variability in response to these medications. A significant proportion of this responsiveness may be heritable.

OBJECTIVES

To investigate whether a genome-wide association study (GWAS) could identify novel pharmacogenetic loci in asthma.

METHODS

We performed a GWAS of acute bronchodilator response (BDR) to inhaled β2-agonists. A total of 444,088 single-nucleotide polymorphisms (SNPs) were examined in 724 individuals from the SNP Health Association Resource (SHARe) Asthma Resource Project (SHARP). The top 50 SNPs were carried forward to replication in a population of 444 individuals.

MEASUREMENTS AND MAIN RESULTS

The combined P value for four SNPs reached statistical genome-wide significance aftercorrecting for multiple comparisons. Combined P values for rs350729, rs1840321, rs1384918, and rs1319797 were 2.21 × 10(-10), 5.75 × 10(-8), 9.3 × 10(-8), and 3.95 × 10(-8), respectively. The significant variants all map to a novel genetic region on chromosome 2 near the ASB3 gene, a region associated with smooth muscle proliferation. As compared with the wild type, the presence of the minor alleles reduced the degree of BDR by 20% in the original population and by a similar percentage in the confirmatory population.

CONCLUSIONS

These GWAS findings for BDR in subjects with asthma suggest that a gene associated with smooth muscle proliferation may influence a proportion of the smooth muscle relaxation that occurs in asthma.

Asthma pharmacogenetics and the development of genetic profiles for personalized medicine

Human genetics research will be critical to the development of genetic profiles for personalized or precision medicine in asthma. Genetic profiles will consist of gene variants that predict individual disease susceptibility and risk for progression, predict which pharmacologic therapies will result in a maximal therapeutic benefit, and predict whether a therapy will result in an adverse response and should be avoided in a given individual. Pharmacogenetic studies of the glucocorticoid, leukotriene, and β₂-adrenergic receptor pathways have focused on candidate genes within these pathways and, in addition to a small number of genome-wide association studies, have identified genetic loci associated with therapeutic responsiveness. This review summarizes these pharmacogenetic discoveries and the future of genetic profiles for personalized medicine in asthma. The benefit of a personalized, tailored approach to health care delivery is needed in the development of expensive biologic drugs directed at a specific biologic pathway. Prior pharmacogenetic discoveries, in combination with additional variants identified in future studies, will form the basis for future genetic profiles for personalized tailored approaches to maximize therapeutic benefit for an individual asthmatic while minimizing the risk for adverse events.

Genetics of allergic diseases

Genome-wide association studies (GWAS) have been employed in the field of allergic disease, and significant associations have been published for nearly 100 asthma genes/loci. An outcome of GWAS in allergic disease has been the formation of national and international collaborations leading to consortia meta-analyses, and an appreciation for the specificity of genetic associations to sub-phenotypes of allergic disease. Molecular genetics has undergone a technological revolution, leading to next-generation sequencing strategies that are increasingly employed to hone in on the causal variants associated with allergic diseases. Unmet needs include the inclusion of diverse cohorts and strategies for managing big data.

Do genetic polymorphisms alter patient response to inhaled bronchodilators?

INTRODUCTION

Short- and long-acting β agonists (SABA and LABA) are bronchodilators for treating asthma. Bronchodilator response (BDR) is quantified by measuring air expired in the first second during a forced expiratory maneuver, prior to and following inhalation of SABA. BDR has been associated with a significant degree of heterogeneity, in part attributable to genetic variation. Heritability, the proportion of phenotypic variability accounted for by genetic variation is estimated to account for 50% of pulmonary function and 28.5% for BDR.

AREAS COVERED

A MEDLINE search for English articles published from January 1990 to June 2014 was completed using the terms: bronchodilator, bronchodilator response, short-acting bronchodilator, long-acting bronchodilator, β2 adrenergic receptor gene (ADRB2), asthma and pharmacogenomics. The effects of ADRB2 variants on BDR and the safety of SABA and LABA + inhaled corticosteroids have been studied with equivocal results. Single and candidate gene studies have identified variants in other genes that alter response to bronchodilators. Associations were recently observed between hospital admission rates and two rare ADRB2 polymorphisms: Thr164Ile and a 25 base pair insertion-deletion at nucleotide -376. This was the first report of life-threatening events associated with LABA being linked to rare ADRB2 variants.

EXPERT OPINION

Pharmacogenomic studies over the last two decades clearly demonstrate that polymorphisms alter patient response to bronchodilators in patients with asthma.

Pharmacogenetics of beta2 adrenergic receptor agonists in asthma management

Beta2 (β2) adrenergic receptor agonists (beta agonists) are a commonly prescribed treatment for asthma despite the small increase in risk for life-threatening adverse responses associated with long-acting beta agonist (LABA). The concern for life-threatening adverse effects associated with LABA and the inter-individual variability of therapeutic responsiveness to LABA-containing combination therapies provide the rationale for pharmacogenetic studies of beta agonists. These studies primarily evaluated genes within the β2-adrenergic receptor and related pathways; however, recent genome-wide studies have identified novel loci for beta agonist response. Recent studies have identified a role for rare genetic variants in determining beta agonist response and, potentially, the risk for rare, adverse responses to LABA. Before genomics research can be applied to the development of genetic profiles for personalized medicine, it will be necessary to continue adapting to the analysis of an increasing volume of genetic data in larger cohorts with a combination of analytical methods and in vitro studies.

Inhaled corticosteroid treatment modulates ZNF432 gene variant's effect on bronchodilator response in asthmatics

BACKGROUND

Single nucleotide polymorphisms (SNPs) influence a patient's response to inhaled corticosteroids and β2-agonists, and the effect of treatment with inhaled corticosteroids is synergistic with the effect of β2-agonists. We hypothesized that use of inhaled corticosteroids could influence the effect of SNPs associated with a bronchodilator response.

OBJECTIVE

To assess whether, among subjects with asthma, the association of SNPs with bronchodilator response is different between those treated with inhaled corticosteroids versus those on placebo.

METHODS

A genome-wide association analysis was conducted by using 581 white subjects from the Childhood Asthma Management Program. By using data for 449,540 SNPs, we conducted a gene by environment analysis in PLINK with inhaled corticosteroid treatment as the environmental exposure and bronchodilator response as the outcome measure. We attempted to replicate the top 12 SNPs in the Leukotriene Modifier or Corticosteroid or Corticosteroid-Salmeterol Trial.

RESULTS

The combined P value for the Childhood Asthma Management Program and Leukotriene Modifier or Corticosteroid or Corticosteroid-Salmeterol Trial populations was 4.8 × 10(-8) for rs3752120, which is located in the zinc finger protein gene ZNF432 and has an unknown function.

CONCLUSIONS

Inhaled corticosteroids appear to modulate the association of bronchodilator response with variant(s) in the ZNF432 gene among adults and children with asthma.

Pharmacogenetics and the development of personalized approaches for combination therapy in asthma

Asthma is a common, chronic disease of the airways that is treated with a combination of different therapies. The combination of LABA and ICS therapy results in a synergistic interaction that is efficacious in improving asthma symptom control; however, genetic variation has the potential to alter therapeutic efficacy. Both agents mediate complex molecular pathways consisting of gene variation that has been investigated with the analysis of candidate genes in the β2-adrenergic receptor and glucocorticoid pathway. These pharmacogenetic studies have been limited to retrospective analyses of clinical trial cohorts and a small number of prospective, genotype-stratified trials. More recently, genome-wide association studies in combination with replication in additional cohorts and in vitro cell-based models have been used to identify novel pathway-related pharmacogenetic variations. This review of the pharmacogenetics of the β2-adrenergic receptor and glucocorticoid pathways highlights the genotypic effects of variation in multiple genes from interacting pathways which may contribute to differential responses to inhaled beta agonists and glucocorticoids. As our understanding of these genetic mechanisms improves, panels of biomarkers may be developed to determine which combination therapies are the most effective with the least risk to an individual asthma patient. Before we can usher in an era of personalized medicine for asthma, it is first important to improve our ability to analyze large volumes of genetic data in large clinical trial cohorts using a combination of study designs, analytical methods, and in vitro functional studies.

Asthma pharmacogenetics: responding to the call for a personalized approach

PURPOSE OF REVIEW

Asthma is a chronic, complex disease that is treated with a combination of different therapies. However, interindividual variability in clinical responses to different therapies complicates asthma management. A personalized approach to asthma management could identify appropriate responders to specific agents or those that might be at an increased risk for adverse responses.

RECENT FINDINGS

Pharmacogenetic studies of genes from the leukotriene, glucocorticoid, and beta2-adrenergic receptor pathways have improved our understanding of how gene variation determines therapeutic responses to different classes of antiasthma therapies. Such studies have previously been limited to retrospective analyses of candidate genes in the leukotriene, glucocorticoid, and beta2-adrenergic receptor pathways in trial cohorts. However, prospective genotype-stratified trials in asthma have recently been done and recent genome-wide association studies have identified novel pharmacogenetic loci.

SUMMARY

It will be important to replicate previous genotypic associations in large clinical trial cohorts as future pharmacogenetic studies continue to focus on genome-wide approaches and the study of novel therapeutic pathways. This review of the pharmacogenetics of asthma highlights the contributions of genomics research to the future of personalized medicine in asthma and draws attention to the role of genetic biomarkers in predicting clinical responses to specific therapies.

A genome-wide association study of bronchodilator response in Latinos implicates rare variants

BACKGROUND

The primary rescue medication to treat acute asthma exacerbation is the short-acting β₂-adrenergic receptor agonist; however, there is variation in how well a patient responds to treatment. Although these differences might be due to environmental factors, there is mounting evidence for a genetic contribution to variability in bronchodilator response (BDR).

OBJECTIVE

To identify genetic variation associated with bronchodilator drug response in Latino children with asthma.

METHODS

We performed a genome-wide association study (GWAS) for BDR in 1782 Latino children with asthma using standard linear regression, adjusting for genetic ancestry and ethnicity, and performed replication studies in an additional 531 Latinos. We also performed admixture mapping across the genome by testing for an association between local European, African, and Native American ancestry and BDR, adjusting for genomic ancestry and ethnicity.

RESULTS

We identified 7 genetic variants associated with BDR at a genome-wide significant threshold (P < 5 × 10(-8)), all of which had frequencies of less than 5%. Furthermore, we observed an excess of small P values driven by rare variants (frequency, <5%) and by variants in the proximity of solute carrier (SLC) genes. Admixture mapping identified 5 significant peaks; fine mapping within these peaks identified 2 rare variants in SLC22A15 as being associated with increased BDR in Mexicans. Quantitative PCR and immunohistochemistry identified SLC22A15 as being expressed in the lung and bronchial epithelial cells.

CONCLUSION

Our results suggest that rare variation contributes to individual differences in response to albuterol in Latinos, notably in SLC genes that include membrane transport proteins involved in the transport of endogenous metabolites and xenobiotics. Resequencing in larger, multiethnic population samples and additional functional studies are required to further understand the role of rare variation in BDR.

A genome-wide association study of bronchodilator response in asthmatics

Reversibility of airway obstruction in response to β2-agonists is highly variable among asthmatics, which is partially attributed to genetic factors. In a genome-wide association study of acute bronchodilator response (BDR) to inhaled albuterol, 534 290 single-nucleotide polymorphisms (SNPs) were tested in 403 white trios from the Childhood Asthma Management Program using five statistical models to determine the most robust genetic associations. The primary replication phase included 1397 polymorphisms in three asthma trials (pooled n=764). The second replication phase tested 13 SNPs in three additional asthma populations (n=241, n=215 and n=592). An intergenic SNP on chromosome 10, rs11252394, proximal to several excellent biological candidates, significantly replicated (P=1.98 × 10(-7)) in the primary replication trials. An intronic SNP (rs6988229) in the collagen (COL22A1) locus also provided strong replication signals (P=8.51 × 10(-6)). This study applied a robust approach for testing the genetic basis of BDR and identified novel loci associated with this drug response in asthmatics.

Polymorphisms in recent GWA identified asthma genes CA10, SGK493, and CTNNA3 are associated with disease severity and treatment response in childhood asthma

Recent genome-wide association studies (GWAs) have identified several new genetic risk factors for asthma; however, their influence on disease behavior and treatment response is still unclear. The aim of our study was the association analysis of the most significant single nucleotide polymorphisms (SNPs) recently reported by GWAs in different phenotypes of childhood asthma and analysis of correlation between these SNPs and clinical parameters. We have genotyped 288 children with asthma and 276 healthy controls. We provided here first replication of bivariate associations between CA10 (p = 0.001) and SGK493 (p = 0.011) with asthma. In addition, we have identified new correlation between SNPs in CA10, SGK493, and CTNNA3 with asthma behavior and glucocorticoid treatment response. Asthma patients who carried G allele in SNP rs967676 in gene CA10 were associated with more pronounced airway obstruction, higher bronchial hyper-reactivity, and increased inflammation. Higher bronchial hyper-reactivity was also associated with C allele in SNP rs1440095 in gene SGK493 but only in nonatopic asthmatics. In addition, we found that patients who carried at least one T allele in SNP rs1786929 in CTNNA3 (p = 0.022) and atopic patients who carried at least one G allele in SNP rs967676 in gene CA10 (p = 0.034) had higher increase in pulmonary function after glucocorticoid therapy. Our results suggest genetic heterogeneity between atopic and nonatopic asthma. We provided further evidence that treatment response in childhood asthma is genetically predisposed, and we report here two novel SNPs in genes CA10 and CTNNA3 as potential pharmacogenetic biomarkers that could be used in personalized treatment in childhood asthma.

Asthma and bronchodilator responsiveness are associated with polymorphic markers of ARG1, CRHR2 and chromosome 17q21

OBJECTIVE

Asthma is caused by complex interactions between multiple genes. β2-Agonist is the standard rescue treatment to relieve asthma symptoms and bronchoconstriction. A genetic study for spirometric parameters helps to predict the responses to this antiasthma treatment. This study investigated the relationship between asthma and bronchodilator responsiveness (BDR) and eight asthma genes.

METHODS

Fifteen single-nucleotide polymorphisms in these genes were genotyped in 345 Chinese asthmatics and 464 controls. Gene-gene interactions were analysed by generalized multifactor dimensionality reduction (GMDR).

RESULTS

The diagnosis of asthma was associated with rs7216389 in ORMDL3 [odds ratio (OR) 0.74 and 95% confidence interval (95% CI) 0.56-0.99] and rs3756780 in ARG1 (OR 0.67, 95% CI 0.51-0.89) and BDR with rs2749935 in ARG1. However, none of these associations remained significant at 5% when adjusted for multiple testing by the Bonferroni correction or a false discovery rate. GMDR analyses revealed that rs7216389 in ORMDL3 and rs3756780 in ARG1 might interact for a risk of asthma. Individuals with high-risk genotypes had OR 1.66 (95% CI 1.24-2.23) for asthma when compared with those with low-risk genotypes. GMDR suggested a two-locus model with rs2749935 in ARG1 and rs2190242 in CRHR2 to be associated with BDR. Specifically, reversibility of forced expiratory volume in 1 s was higher in high-risk than that in low-risk patients [mean (95% CI): 10.7 (8.6-12.9) vs. 6.8 (5.9-7.6)%]; with the latter group showing higher forced expiratory volume in 1 s reversibility compared with high-risk controls [2.8 (1.4-4.3)%].

CONCLUSION

ARG1 and ORMDL3 may interact to determine the risk of asthma and ARG1 and CRHR2 to alter BDR in asthmatics. Nonetheless, this study is only hypothesis-generating as none of the single marker comparisons is significant when adjusted for multiple testing. These findings need to be confirmed in independent populations.

Genome-wide association analysis in asthma subjects identifies SPATS2L as a novel bronchodilator response gene

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.

Corticotropin-releasing hormone receptor-1 and 2 activity produces divergent resistance against stress-induced pulmonary Streptococcus pneumoniae infection

Utilizing a murine model of S. pneumoniae infection and restraint stress, we determined how corticotropin releasing hormone (CRH-R) receptors impacts disease. CRH-R1 (antalarmin) and CRH-R2 (astressin2B) antagonists were administered intraperitoneally prior to restraint stress followed by pulmonary S. pneumoniae infection. CRH-R1 inhibition is not protective against pneumococcal disease induced by stress. Conversely, CRH-R2 inhibition attenuates stress-induced bacterial growth and significantly prevented severe sepsis. Neutrophillic responses were associated with CRH receptor-specific disease outcome providing a potential cellular target for stress-induced susceptibility to the development of severe pneumococcal disease. CRH receptor-mediated effects on immune responses could prove valuable for novel therapeutics.

Predicting response to short-acting bronchodilator medication using Bayesian networks

AIMS

Bronchodilator response tests measure the effect of beta(2)-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.

RESULTS

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).

CONCLUSION

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.

Genetic predictors of response to therapy in childhood asthma

Asthma is a common chronic condition in children, where the response to treatment can be heterogeneous within a population. Genetic variations may partly explain the inconsistent response to asthma treatment between individuals. There is a relatively small but consistent body of literature linking genetic variations to improved response to different classes of asthma treatment, including short- and long-acting beta-agonists, corticosteroids, and leukotriene modifiers. In most cases, the advantage conferred by a single genetic mutation for treatment response is relatively small; the Arg16Gly single nucleotide polymorphism of the beta2-adrenoceptor is the exception to this rule and is associated with a marked difference in response to short-acting beta-agonists. Pharmacogenetic studies have only recently been undertaken in asthmatic individuals, and much more work is required before clinical applications arise. Future genome-wide association (GWA) studies and randomized controlled trials in genetically susceptible populations will determine whether asthma treatment can be tailored to an individual based on their DNA. The aim of the present paper is to review pharmacogenetic studies concerning asthma medications, with a primary focus on studies involving children.

The pharmacogenetics of asthma treatment

The treatment response to each of the three major classes of asthma medications-beta agonists, leukotriene modifiers, and inhaled corticosteroids-demonstrates substantial interindividual variability. Evidence indicates that this variability is mediated, at least in part, by genetic factors. Pharmacogenetics is the study of the role of heritable factors in the response to pharmacologic therapy. The goal of pharmacogenetics is "predictive medicine," whereby a genetic profile, combined with clinical characteristics, can be used to predict response to medications a priori, allowing for maximal therapeutic response while minimizing side effects. In this review, we discuss the rationale behind conducting asthma pharmacogenetics studies, provide an overview of asthma pharmacogenetic phenotypes, and detail the most important results of asthma pharmacogenetics studies conducted to date. Although no specific predictive tests have been developed thus far, the existing studies serve as strong proof of concept of the applicability of pharmacogenetics in the future management of asthma.