CACNA1C polymorphisms are associated with the efficacy of calcium channel blockers in the treatment of hypertension

Genetic polymorphisms influencing antihypertensive drug responses

Hypertension is a major contributor to cardiovascular disease and its associated morbidity and mortality. The low efficacy observed with some anti-hypertensive therapies has been attributed partly to inter-individual genetic variability. This paper reviews the major findings regarding these genetic variabilities that modulate responses to anti-hypertensive therapies such as angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), diuretics, calcium channel blockers (CCBs) and β-adrenoceptor blockers. The importance of studying these genetic polymorphisms stems from the goal to optimise anti-hypertensive therapy for each individual patient, aiming for the highest efficacy and lowest risk of adverse effects. It is important to recognise that environmental and epigenetic factors can contribute to the observed variations in drug responses. Owing to the multigenic and multifactorial nature of drug responses, further research is crucial for translating these findings into clinical practice and the establishment of reliable recommendations.

Genomic Insights into Blood Pressure Regulation: Exploring Ion Channel and Transporter Gene Variations in Jordanian Hypertensive Individuals

Background and Objectives: Hypertension (HTN) constitutes a significant global health burden, yet the specific genetic variant responsible for blood pressure regulation remains elusive. This study investigates the genetic basis of hypertension in the Jordanian population, focusing on gene variants related to ion channels and transporters, including KCNJ1, WNK1, NPPA, STK39, LUC7L2, NEDD4L, NPHS1, BDKRB2, and CACNA1C. Materials and Methods: This research involved 200 hypertensive patients and 224 healthy controls. Whole blood samples were collected from each participant, and genomic DNA was extracted. The genetic distribution of the polymorphisms was analyzed. The haplotype frequencies were investigated using the SNPStats web tool, and the genotype and allele frequencies of the studied variants were assessed using the χ2 test. Results: Sixteen single nucleotide polymorphisms (SNPs) from nine genes were evaluated. A significant association was observed between the rs880054 variant of the WNK1 gene and hypertension susceptibility, with the T allele elevating the risk of hypertension. This association remained important in the codominant model (p = 0.049) and the dominant model (p = 0.029). In addition, rs880054 was associated with clinical characteristics such as triglyceride levels and cerebrovascular accidents (p-value > 0.05). Conclusions: Our findings reveal a significant link between the rs880054 SNP and an increased hypertension risk, suggesting that variations in WNK1 may be crucial in regulating blood pressure. This study provides new insights into the genetic factors contributing to hypertension and highlights the potential of WNK1 as a target for future therapeutic interventions.

Pharmacogenomic Study of Selected Genes Affecting Amlodipine Blood Pressure Response in Patients with Hypertension

Introduction

Despite the availability of various antihypertensive medications, the response to these medications varies among individuals. Understanding how individual genetic variations affect drugs treatment outcomes is a key area of focus in precision medicine. This study investigated the correlation between single nucleotide polymorphisms (SNPs) in selected genes (CACNA1C, CACNA1D, ABCB1, ACE, ADBR2, and NOS1AP) and the blood pressure (BP) control by amlodipine.

Methods

Four hundred individuals of Pashtun ethnicity undergoing amlodipine treatment for hypertension were included in the present study and divided into the controlled (BP less than 140/90 mmHg) and uncontrolled (BP greater than 140/90 mmHg) hypertension groups. Blood samples (3 mL) were collected from each participant, and DNA was extracted using the Kit method. Ten SNPs in amlodipine pharmacogenes were selected and genotyped using real-time PCR with the TaqMan® system. Logistic regression model was used to determine the association between SNPs and the amlodipine BP response.

Results

Notable association were observed between SNP rs2239050/CACNA1C and amlodipine blood pressure response, with GG genotype carriers demonstrating a better response (P=0.004) than individuals carrying CC or CG genotypes. SNP rs312481/CACNA1D also exhibited a positive pharmacogenetic association, Individuals with the GG genotype showing a considerable reduction in BP (P=0.021) compared to participants with AA or GA genotypes. In case of SNP rs429/ACE individuals carrying TA genotype were less likely to achieve BP control (P=0.002) than AA genotype carriers.

Conclusion

Our finding suggests that the SNPs rs2239050/CACNA1C, rs312481/CACNA1D and rs429/ACE influence amlodipine blood pressure response in patients with hypertension. It is recommended that prior knowledge of amlodipine associated pharmacogenetic variants is important that could improve its treatment outcomes in hypertensive patients.

Pharmacogenomics of Preeclampsia therapies: Current evidence and future challenges for clinical implementation

Preeclampsia is a pregnancy-specific disorder, and it is a leading cause of maternal and perinatal morbidity and mortality. The application of pharmacogenetics to antihypertensive agents and dose selection in women with preeclampsia is still in its infancy. No current prescribing guidelines from the clinical pharmacogenetics implementation consortium (CPIC) exist for preeclampsia. Although more studies on pharmacogenomics are underway, there is some evidence for the pharmacogenomics of preeclampsia therapies, considering both the pharmacokinetic (PK) and pharmacodynamic (PD) properties of drugs used in preeclampsia. It has been revealed that the CYP2D6*10 variant is significantly higher in women with preeclampsia who are non-responsive to labetalol compared to those who are in the responsive group. Various genetic variants of PD targets, i.e., NOS3, MMP9, MMP2, TIMP1, TIMP3, VEGF, and NAMPT, have been investigated to assess the responsiveness of antihypertensive therapies in preeclampsia management, and they indicated that certain genetic variants of MMP9, TIMP1, and NAMPT are more frequently observed in those who are non-responsive to anti-hypertensive therapies compared to those who are responsive. Further, gene-gene interactions have revealed that NAMPT, TIMP1, and MMP2 genotypes are associated with an increased risk of preeclampsia, and they are more frequently observed in the non-responsive subgroup of women with preeclampsia. The current evidence is not rigorous enough for clinical implementation; however, an institutional or regional-based retrospective analysis of audited data may help close the knowledge gap during the transitional period from a traditional approach (a "one-size-fits-all" strategy) to the pharmacogenomics of preeclampsia therapies.

Single Nucleotide Polymorphisms in Amlodipine-Associated Genes and Their Correlation with Blood Pressure Control among South African Adults with Hypertension

Objective: This study describes the single nucleotide polymorphisms (SNPs) in amlodipine-associated genes and assesses their correlation with blood pressure control among South African adults with hypertension. Methods: In total, 304 hypertensive patients on amlodipine treatment belonging to the indigenous Swati, Xhosa and Zulu population groups of South Africa were recruited between June 2017 and June 2019. Participants were categorized into: controlled (blood pressure < 140/90 mmHg) and uncontrolled (blood pressure ≥ 140/90 mmHg) hypertension. Thirteen SNPs in amlodipine pharmacogenes with a high PharmGKB evidence base were selected and genotyped using MassArray (Agena BioscienceTM). Logistic regression was fitted to identify significant associations between the SNPs and blood pressure control with amlodipine. Results: The majority of the participants were females (76.6%), older than 45 years (89.1%) and had uncontrolled hypertension (52.3%). Of the 13 SNPs genotyped, five SNPs, rs1042713 (minor allele frequency = 45.9%), rs10494366 (minor allele frequency = 35.3%), rs2239050 (minor allele frequency = 28.7%), rs2246709 (minor allele frequency = 51.6%) and rs4291 (minor allele frequency = 34.4%), were detected among the Xhosa participants, while none were detected among the Swati and Zulu tribal groups. Variants rs1042713 and rs10494366 demonstrated an expression frequency of 97.5% and 79.5%, respectively. Variant TA genotype of rs4291 was significantly associated with uncontrolled hypertension. No association was established between blood pressure response to amlodipine and the remaining four SNPs. Conclusions: This study reports the discovery of five SNPs in amlodipine genes (rs2239050, rs2246709, rs4291, rs1042713 and rs10494366) among the indigenous Xhosa-speaking tribe of South Africa. In addition, the TA genotype of rs4291 was associated with blood pressure control in this cohort. These findings might open doors for more pharmacogenomic studies, which could inform innovations to personalised anti-hypertensive treatment in the ethnically diverse population of South Africa.

Genetic Contributors of Efficacy and Adverse Metabolic Effects of Chlorthalidone in African Americans from the Genetics of Hypertension Associated Treatments (GenHAT) Study

Hypertension is a leading risk factor for cardiovascular disease mortality. African Americans (AAs) have the highest prevalence of hypertension in the United States, and to alleviate the burden of hypertension in this population, better control of blood pressure (BP) is needed. Previous studies have shown considerable interpersonal differences in BP response to antihypertensive treatment, suggesting a genetic component. Utilizing data from 4297 AA participants randomized to chlorthalidone from the Genetics of Hypertension Associated Treatments (GenHAT) study, we aimed to identify variants associated with the efficacy of chlorthalidone. An additional aim was to find variants that contributed to changes in fasting glucose (FG) in these individuals. We performed genome-wide association analyses on the change of systolic and diastolic BP (SBP and DBP) over six months and FG levels over 24 months of treatment. We sought replication in the International Consortia of Pharmacogenomics Studies. We identified eight variants statistically associated with BP response and nine variants associated with FG response. One suggestive LINC02211-CDH9 intergenic variant was marginally replicated with the same direction of effect. Given the impact of hypertension in AAs, this study implies that understanding the genetic background for BP control and glucose changes during chlorthalidone treatment may help prevent adverse cardiovascular events in this population.

Polymorphisms in common antihypertensive targets: Pharmacogenomic implications for the treatment of cardiovascular disease

The idea of personalized medicine came to fruition with sequencing the human genome; however, aside from a few cases, the genetic revolution has yet to materialize. Cardiovascular diseases are the leading cause of death globally, and hypertension is a common prelude to nearly all cardiovascular diseases. Thus, hypertension is an ideal candidate disease to apply tenants of personalized medicine to lessen cardiovascular disease. Herein is a survey that visually depicts the polymorphisms in the top eight antihypertensive targets. Although there are numerous genome-wide association studies regarding cardiovascular disease, few studies look at the effects of receptor polymorphisms on drug treatment. With 17,000+ polymorphisms in the combined target proteins examined, it is expected that some of the clinical variability in the treatment of hypertension is due to polymorphisms in the drug targets. Recent advances in techniques and technology, such as high throughput examination of single mutations, structure prediction, computational power for modeling, and CRISPR models of point mutations, allow for a relatively rapid and comprehensive examination of the effects of known and future polymorphisms on drug affinity and effects. As hypertension is easy to measure and has a plethora of clinically viable ligands, hypertension makes an excellent disease to study pharmacogenomics in the lab and the clinic. If the promises of personalized medicine are to materialize, a concerted effort to examine the effects polymorphisms have on drugs is required. A clinician with the knowledge of a patient's genotype can then prescribe drugs that are optimal for treating that specific patient.

The rs1458038 variant near FGF5 is associated with poor response to calcium channel blockers among Filipinos

Genetic variation is known to affect response to calcium channel blockers (CCBs) among different populations. This study aimed to determine the genetic variations associated with poor response to this class of antihypertensive drugs among Filipinos.One hundred eighty one hypertensive participants on CCBs therapy were included in an unmatched case-control study. Genomic deoxyribonucleic acid were extracted and genotyped for selected genetic variants. Regression analysis was used to determine the association of genetic and clinical variables with poor response to medication.The variant rs1458038 near fibroblast growth factor 5 gene showed significant association with poor blood pressure-lowering response based on additive effect (CT genotype: adjusted OR 3.41, P = .001; TT genotype: adjusted OR 6.72, P < .001).These findings suggest that blood pressure response to calcium channels blockers among Filipinos with hypertension is associated with gene variant rs1458038 near fibroblast growth factor 5 gene. Further studies are recommended to validate such relationship of the variant to the CCB response.

CACNA1C rs1006737 SNP increases the risk of essential hypertension in both Chinese Han and ethnic Russian people of Northeast Asia

Voltage-gated Ca2+ channels play a key role in the regulation of arterial tone and blood pressure. The aim of this study was to determine whether the association of calcium voltage-gated channel subunit alpha1 C (CACNA1C) rs1006737 with essential hypertension (EH) exists in both Chinese Han and ethnic Russian populations of Northeast Asia. We used a case-control study of 2 ethnic groups in the same latitude geographical area to investigate the association between the susceptibility of EH and rs1006737 polymorphism. A total of 1512 EH patients and 1690 controls in Chinese Han people (Heilongjiang Provence, China), 250 EH patients, and 250 controls in ethnic Russian people (Chita, Russia), participated in this study. All participants were genotyped using the TaqMan SNP genotyping assay (Agena Company). Baseline characteristics and the minor allele frequencies of rs1006737 vary substantially among common Chinese Han and ethnic Russian people. Allele A was found to be a risk factor for EH in Chinese Han [(odds ratio) OR 1.705, (confidence interval) 95% CI: 1.332-2.182, P < .001] and ethnic Russian (OR 1.437; 95% CI: 1.110-1.860, P = .006). The GA genotype was significantly associated with an increased risk of hypertension (OR 1.538, 95% CI: 1.188-1.991, P = .001) for Chinese Han people, and the AA genotype (OR 2.412, 95% CI: 1.348-4.318, P = .003) for ethnic Russian people. The results of this study indicate that the A allele of the variant rs1006737 in the CACNA1C gene may be a useful genetic marker for EH risk prediction in Chinese Han and ethnic Russian populations.

Pharmacogenomics of Hypertension Treatment

Hypertension is one of the strongest modifiable cardiovascular risk factors, affecting an increasing number of people worldwide. Apart from poor medication adherence, the low efficacy of some therapies could also be related to inter-individual genetic variability. Genetic studies of families revealed that heritability accounts for 30% to 50% of inter-individual variation in blood pressure (BP). Genetic factors not only affect blood pressure (BP) elevation but also contribute to inter-individual variability in response to antihypertensive treatment. This article reviews the recent pharmacogenomics literature concerning the key classes of antihypertensive drugs currently in use (i.e., diuretics, β-blockers, ACE inhibitors, ARB, and CCB). Due to the numerous studies on this topic and the sometimes-contradictory results within them, the presented data are limited to several selected SNPs that alter drug response. Genetic polymorphisms can influence drug responses through genes engaged in the pathogenesis of hypertension that are able to modify the effects of drugs, modifications in drug–gene mechanistic interactions, polymorphisms within drug-metabolizing enzymes, genes related to drug transporters, and genes participating in complex cascades and metabolic reactions. The results of numerous studies confirm that genotype-based antihypertension therapies are the most effective and may help to avoid the occurrence of major adverse events, as well as decrease the costs of treatment. However, the genetic heritability of drug response phenotypes seems to remain hidden in multigenic and multifactorial complex traits. Therefore, further studies are required to analyze all associations and formulate final genome-based treatment recommendations.

Pharmacogenomics of amlodipine and hydrochlorothiazide therapy and the quest for improved control of hypertension: a mini review

Blood pressure (BP) is a complex trait that is regulated by multiple physiological pathways and include but is not limited to extracellular fluid volume homeostasis, cardiac contractility, and vascular tone through renal, neural, or endocrine systems. Uncontrolled hypertension (HTN) has been associated with an increased mortality risk. Therefore, understanding the genetics that underpins and influence BP regulation will have a major impact on public health. Moreover, uncontrolled HTN has been linked to inter-individual variation in the drugs’ response and this has been associated with an individual’s genetics architecture. However, the identification of candidate genes that underpin the genetic basis of HTN remains a major challenge. To date, few variants associated with inter-individual BP regulation have been identified and replicated. Research in this field has accelerated over the past 5 years as a direct result of on-going genome-wide association studies (GWAS) and the progress in the identification of rare gene variants and mutations, epigenetic markers, and the regulatory pathways involved in the pathophysiology of BP. In this review we describe and enhance our current understanding of how genetic variants account for the observed variability in BP response in patients on first-line antihypertensive drugs, amlodipine and hydrochlorothiazide.

Pharmacogenomics And Hypertension: Current Insights

Hypertension is a multifactorial disease that affects approximately one billion subjects worldwide and is a major risk factor associated with cardiovascular events, including coronary heart disease and cerebrovascular accidents. Therefore, adequate blood pressure control is important to prevent these events, reducing premature mortality and disability. However, only one third of patients have the effective control of blood pressure, despite several classes of antihypertensive drugs available. These disappointing outcomes may be at least in part explained by interpatient variability in drug response due to genetic polymorphisms. To address the effects of genetic polymorphisms on blood pressure responses to the antihypertensive drug classes, studies have applied candidate genes and genome wide approaches. More recently, a third approach that considers gene-gene interactions has also been applied in hypertension pharmacogenomics. In this article, we carried out a comprehensive review of recent findings on the pharmacogenomics of antihypertensive drugs, including diuretics, β-blockers, angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, and calcium channel blockers. We also discuss the limitations and inconsistences that have been found in hypertension pharmacogenomics and the challenges to implement this valuable approach in clinical practice.

Association study of CACNA1C polymorphisms with large artery atherosclerotic stroke in Chinese Han population

Aims Ischemic stroke (IS) is one of the most common diseases of neurology and the main cause of death and disability in Chinese population. CACNA1C was considered to be involved in the process of atherosclerosis, but there was little information about the association between genotypic polymorphisms of CACNA1C and ischemic stroke. Our study was designed to elucidate the relationship between four single-nucleotide polymorphisms (SNPs) variants in CACNA1C gene and the risk of large-artery atherosclerotic (LAA) stroke patients. Methods A total of 384 subjects were enrolled in this study, including 192 LAA stroke cases and 192 healthy controls. And four SNPs variants in CNCNA1C gene were genotyped using in-house developed multiplex tagged-amplicon deep sequencing (TAm-Seq). Statistical analysis were conducted using χ2 test and binary logistic regression analysis. Results We found one variant was significantly associated with LAA stroke in the allele models (rs10848683, p = 0.036, OR = 1.371, 95%CI: 1.021-1.841). And rs10848683 was also found to associate with LAA stroke under recessive model (p = 0.027, OR = 0.618, 95% CI: 0.403-0.947) after adjustment for gender and age. We also found that significant difference existed between haplotypes (rs229961-rs215976-rs216008-rs10848683) and LAA stroke (C-T-C-C, p = 0.017, OR = 2.265, 95%CI: 1.136-4.518; G-C-C-C, p = 0.046, OR = 1.891, 95% CI: 1.003-3.565; C-T-C-T, p = 0.001, OR = 0.256, 95%CI: 0.101-0.645). Conclusion The results suggested that there was a potential association between CNCNA1C gene and the risk factor of LAA stroke in Chinese Han population.

Translational Systems Pharmacology Studies in Pregnant Women

Pregnancy involves rapid physiological adaptation and complex interplay between mother and fetus. New analytic technologies provide large amounts of genomic, proteomic, and metabolomics data. The integration of these data through bioinformatics, statistical, and systems pharmacology techniques can improve our understanding of the mechanisms of normal maternal physiologic changes and fetal development. New insights into the mechanisms of pregnancy‐related disorders, such as preterm birth (PTB), may lead to the development of new therapeutic interventions and novel biomarkers.

Role of CACNA1C gene polymorphisms and protein expressions in the pathogenesis of schizophrenia: a case-control study in a Chinese population

The study aimed to investigate the correlations of CACNA1C genetic polymorphisms and protein expression with the pathogenesis of schizophrenia in a Chinese population. This research included 139 patients diagnosed with schizophrenia (case group) and 141 healthy volunteers (control group). Case and control samples were genotyped using denaturing high-performance liquid chromatography (DHPLC). Haplotypes of rs10848683, rs2238032, and rs2299661 were analyzed using the Shesis software. A mouse model of schizophrenia was established and assigned to test and blank groups. Western blotting was used to detect CACNA1C protein expression. The genotype and allele distribution of rs2238032 and rs2299661 differed between the case and control groups. TT genotype of rs2238032 and G allele of rs2299661 could potentially reduce the risk of schizophrenia. The distribution of rs2238032 genotype has a close connection with cognitive disturbance and the results of the general psychopathology classification exam. The distribution of rs2299661 genotypes was closely related to sensory and perceptual disorders, negative symptom subscales, and the results of the general psychopathology classification exam. CTC haplotype increased and CTG decreased the risk of schizophrenia in healthy people. In the brain tissues of mice with schizophrenia, the CACNA1C protein expression was higher in the test group than in the blank group. Our study demonstrated that CACNA1C gene polymorphisms and CACNA1C protein expression were associated with schizophrenia and its clinical phenotypes.

Association between CACNA1C gene polymorphisms and ritodrine-induced adverse events in preterm labor patients

PURPOSE

As a tocolytic agent, ritodrine has been used in European and Asian countries but has lost popularity due to safety concerns. This study aimed to investigate the relationship between adverse drug events caused by ritodrine and the CACNA1C polymorphisms in preterm labor patients.

METHODS

Data were collected from medical records including maternal age, gestational age, body mass index, dilation score, effacement score, modified Bishop score, maximum infusion rate, and adverse drug events. Five single-nucleotide polymorphisms of the CACNA1C gene (rs10774053, rs215994, rs215976, rs2239128, and rs2041135) were analyzed.

RESULTS

One hundred eighty-six patients were included, 33 of whom had adverse drug events. A allele carriers of rs10774053 showed about 0.293-fold lower adverse drug events than GG genotype carriers (p = 0.012, absolute risk reduction = 16.5%) after adjusting for other confounding variables; the number needed to genotype for preventing one patient with GG genotype from suffering higher incidence of adverse drug events was calculated to be 14.6. Increase in maximum infusion rate of 1 mL/h was associated with a 1.03-fold (95% CI 1.01~1.06, p = 0.005) increased risk of adverse drug events. None of the patients with a CC genotype of rs215994 had adverse drug events, whereas 22.1% of the T allele carriers had adverse drug events.

CONCLUSION

This study showed that CACNA1C gene polymorphisms could alter the probability of adverse drug event risk when ritodrine is used in preterm labor.

Associations of Variants in the CACNA1A and CACNA1C Genes With Longitudinal Blood Pressure Changes and Hypertension Incidence: The GenSalt Study

BACKGROUND

We aimed to examine the associations of voltage-dependent calcium-channel genes CACNA1A and CACNA1C with blood pressure (BP) changes and hypertension incidence in a longitudinal family study.

METHODS

A total of 1,768 Han Chinese participants from the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) follow-up study were eligible for the current study. Nine BP measurements were obtained at baseline and each follow-up visit using a random-zero sphygmomanometer. Mixed-effect models were used to assess additive associations of 176 tag single-nucleotide polymorphisms (SNPs) in CACNA1A and CACNA1C with longitudinal BP changes and hypertension incidence. The truncated product method was used for gene-based analysis. The Bonferroni correction was used for adjustment of multiple testing.

RESULTS

During an average of 7.2 years of follow-up, 512 (32.1%) participants developed hypertension. CACNA1A SNP rs8182538 was significantly associated with longitudinal diastolic BP (DBP) change after Bonferroni correction ( Pinteraction = 9.90×10 -5 ), with mean DBP increases of 0.85, 1.03, and 1.19mm Hg per year for participants with genotypes C/C , C/T , and T/T , respectively. A similar trend was observed for the association of rs8182538 with systolic BP (SBP) change. In the gene-based analysis, CACNA1A and CACNA1C were significantly associated with DBP change ( P = 2.0×10 -5 ) and SBP change ( P = 1.4×10 -4 ) after Bonferroni correction, respectively. The gene-based associations remained significant after removing rs8182538 within CACNA1A and rs758116 within CACNA1C in sensitivity analysis.

CONCLUSIONS

Our findings indicated that CACNA1A and CACNA1C might contribute to BP changes over time in Han Chinese population. Further replication of these findings is warranted.

A Physiologic Approach to the Pharmacogenomics of Hypertension

Hypertension is a multifactorial condition with diverse physiological systems contributing to its pathogenesis. Individuals exhibit significant variation in their response to antihypertensive agents. Traditional markers, such as age, gender, diet, plasma renin level, and ethnicity, aid in drug selection. However, this review explores the contribution of genetics to facilitate antihypertensive agent selection and predict treatment efficacy. The findings, reproducibility, and limitations of published studies are examined, with emphasis placed on candidate genetic variants affecting drug metabolism, the renin-angiotensin system, adrenergic signalling, and renal sodium reabsorption. Single-nucleotide polymorphisms identified and replicated in unbiased genome-wide association studies of hypertension treatment are reviewed to illustrate the evolving understanding of the disease's complex and polygenic pathophysiology. Implementation efforts at academic centers seek to overcome barriers to the broad adoption of pharmacogenomics in the treatment of hypertension. The level of evidence required to support the implementation of pharmacogenomics in clinical practice is considered.

Is personalized medicine achievable in obstetrics?

Personalized medicine seeks to identify the right dose of the right drug for the right patient at the right time. Typically, individualization of therapy is based on the pharmacogenomic makeup of the individual and environmental factors that alter drug disposition and response. In addition to these factors, during pregnancy, a woman's body undergoes many changes that can impact the therapeutic efficacy of medications. Yet, there is minimal research regarding personalized medicine in obstetrics. Adoption of pharmacogenetic testing into the obstetrical care is dependent on evidence of analytical validity, clinical validity, and clinical utility. Here, we briefly present information regarding the potential utility of personalized medicine for treating the obstetric patient for pain with narcotics, hypertension, and preterm labor, and discuss the impediments of bringing personalized medicine to the obstetrical clinic.

A rare mutation of CACNA1C in a patient with bipolar disorder, and decreased gene expression associated with a bipolar-associated common SNP of CACNA1C in brain

Timothy Syndrome (TS) is caused by very rare exonic mutations of the CACNA1C gene that produce delayed inactivation of Cav1.2 voltage-gated calcium channels during cellular action potentials, with greatly increased influx of calcium into the activated cells. The major clinical feature of this syndrome is a long QT interval that results in cardiac arrhythmias. However, TS also includes cognitive impairment, autism and major developmental delays in many of the patients. We observed the appearance of bipolar disorder (BD) in a patient with a previously reported case of TS, who is one of the very few patients to survive childhood. This is most interesting because the common single-nucleotide polymorphism (SNP) most highly associated with BD is rs1006737, which we show here is a cis-expression quantitative trait locus for CACNA1C in human cerebellum, and the risk allele (A) is associated with decreased expression. To combine the CACNA1C perturbations in the presence of BD in this patient and in patients with the common CACNA1C SNP risk allele, we would propose that either increase or decrease in calcium influx in excitable cells can be associated with BD. In treatment of BD with calcium channel blocking drugs, we would predict better response in patients without the risk allele, because they have increased CACNA1C expression.

Pathways-driven sparse regression identifies pathways and genes associated with high-density lipoprotein cholesterol in two Asian cohorts

Standard approaches to data analysis in genome-wide association studies (GWAS) ignore any potential functional relationships between gene variants. In contrast gene pathways analysis uses prior information on functional structure within the genome to identify pathways associated with a trait of interest. In a second step, important single nucleotide polymorphisms (SNPs) or genes may be identified within associated pathways. The pathways approach is motivated by the fact that genes do not act alone, but instead have effects that are likely to be mediated through their interaction in gene pathways. Where this is the case, pathways approaches may reveal aspects of a trait's genetic architecture that would otherwise be missed when considering SNPs in isolation. Most pathways methods begin by testing SNPs one at a time, and so fail to capitalise on the potential advantages inherent in a multi-SNP, joint modelling approach. Here, we describe a dual-level, sparse regression model for the simultaneous identification of pathways and genes associated with a quantitative trait. Our method takes account of various factors specific to the joint modelling of pathways with genome-wide data, including widespread correlation between genetic predictors, and the fact that variants may overlap multiple pathways. We use a resampling strategy that exploits finite sample variability to provide robust rankings for pathways and genes. We test our method through simulation, and use it to perform pathways-driven gene selection in a search for pathways and genes associated with variation in serum high-density lipoprotein cholesterol levels in two separate GWAS cohorts of Asian adults. By comparing results from both cohorts we identify a number of candidate pathways including those associated with cardiomyopathy, and T cell receptor and PPAR signalling. Highlighted genes include those associated with the L-type calcium channel, adenylate cyclase, integrin, laminin, MAPK signalling and immune function.

EINVis: a visualization tool for analyzing and exploring genetic interactions in large-scale association studies

Epistasis (gene-gene interaction) detection in large-scale genetic association studies has recently drawn extensive research interests as many complex traits are likely caused by the joint effect of multiple genetic factors. The large number of possible interactions poses both statistical and computational challenges. A variety of approaches have been developed to address the analytical challenges in epistatic interaction detection. These methods usually output the identified genetic interactions and store them in flat file formats. It is highly desirable to develop an effective visualization tool to further investigate the detected interactions and unravel hidden interaction patterns. We have developed EINVis, a novel visualization tool that is specifically designed to analyze and explore genetic interactions. EINVis displays interactions among genetic markers as a network. It utilizes a circular layout (specially, a tree ring view) to simultaneously visualize the hierarchical interactions between single nucleotide polymorphisms (SNPs), genes, and chromosomes, and the network structure formed by these interactions. Using EINVis, the user can distinguish marginal effects from interactions, track interactions involving more than two markers, visualize interactions at different levels, and detect proxy SNPs based on linkage disequilibrium. EINVis is an effective and user-friendly free visualization tool for analyzing and exploring genetic interactions. It is publicly available with detailed documentation and online tutorial on the web at http://filer.case.edu/yxw407/einvis/.

Understanding alternative splicing of Cav1.2 calcium channels for a new approach towards individualized medicine

Calcium channel blockers (CCBs) are widely used to treat cardiovascular diseases such as hypertension, angina pectoris, hypertrophic cardiomyopathy, and supraventricular tachycardia. CCBs selectively inhibit the inward flow of calcium ions through voltage-gated calcium channels, particularly Ca_v1.2, that are expressed in the cardiovascular system. Changes to the molecular structure of Ca_v1.2 channels could affect sensitivity of the channels to blockade by CCBs. Recently, extensive alternative splicing was found in Ca_v1.2 channels that generated wide phenotypic variations. Cardiac and smooth muscles express slightly different, but functionally important Ca_v1.2 splice variants. Alternative splicing could also modulate the gating properties of the channels and giving rise to different responses to inhibition by CCBs. Importantly, alternative splicing of Ca_v1.2 channels may play an important role to influence the outcome of many cardiovascular disorders. Therefore, the understanding of how alternative splicing impacts Ca_v1.2 channels pharmacology in various diseases and different organs may provide the possibility for individualized therapy with minimal side effects.

Autonomic and hemodynamic origins of pre-hypertension: central role of heredity

OBJECTIVES

The purpose of this study is to better understand the origins and progression of pre-hypertension.

BACKGROUND

Pre-hypertension is a risk factor for progression to hypertension, cardiovascular disease, and increased mortality. We used a cross-sectional twin study design to examine the role of heredity in likely pathophysiological events (autonomic or hemodynamic) in pre-hypertension.

METHODS

Eight hundred twelve individuals (337 normotensive, 340 pre-hypertensive, 135 hypertensive) were evaluated in a sample of twin pairs, their siblings, and other family members. They underwent noninvasive hemodynamic, autonomic, and biochemical testing, as well as estimates of trait heritability (the percentage of trait variance accounted for by heredity) and pleiotropy (the genetic covariance or shared genetic determination of traits) by variance components.

RESULTS

In the hemodynamic realm, an elevation of cardiac contractility prompted increased stroke volume, in turn increasing cardiac output, which elevated blood pressure into the pre-hypertension range. Autonomic monitoring detected an elevation of norepinephrine secretion plus a decline in cardiac parasympathetic tone. Twin pair variance components documented substantial heritability as well as joint genetic determination for blood pressure and the contributory autonomic and hemodynamic traits. Genetic variation at a pathway locus also indicated pleiotropic effects on contractility and blood pressure.

CONCLUSIONS

Elevated blood pressure in pre-hypertension results from increased cardiac output, driven by contractility as well as heart rate, which may reflect both diminished parasympathetic and increased sympathetic tone. In the face of increased cardiac output, systemic vascular resistance fails to decline homeostatically. Such traits display substantial heritability and shared genetic determination, although by loci not yet elucidated. These findings clarify the role of heredity in the origin of pre-hypertension and its autonomic and hemodynamic pathogenesis. The results also establish pathways that suggest new therapeutic targets for pre-hypertension, or approaches to its prevention.

The role of genetics in pre-eclampsia and potential pharmacogenomic interventions

The pregnancy-specific condition pre-eclampsia not only affects the health of mother and baby during pregnancy but also has long-term consequences, increasing the chances of cardiovascular disease in later life. It is accepted that pre-eclampsia has a placental origin, but the pathogenic mechanisms leading to the systemic endothelial dysfunction characteristic of the disorder remain to be determined. In this review we discuss some key factors regarded as important in the development of pre-eclampsia, including immune maladaptation, inadequate placentation, oxidative stress, and thrombosis. Genetic factors influence all of these proposed pathophysiological mechanisms. The inherited nature of pre-eclampsia has been known for many years, and extensive genetic studies have been undertaken in this area. Genetic research offers an attractive strategy for studying the pathogenesis of pre-eclampsia as it avoids the ethical and practical difficulties of conducting basic science research during the preclinical phase of pre-eclampsia when the underlying pathological changes occur. Although pharmacogenomic studies have not yet been conducted in pre-eclampsia, a number of studies investigating treatment for essential hypertension are of relevance to therapies used in pre-eclampsia. The pharmacogenomics of antiplatelet agents, alpha and beta blockers, calcium channel blockers, and magnesium sulfate are discussed in relation to the treatment and prevention of pre-eclampsia. Pharmacogenomics offers the prospect of individualized patient treatment, ensuring swift introduction of optimal treatment whilst minimizing the use of inappropriate or ineffective drugs, thereby reducing the risk of harmful effects to both mother and baby.

Phenotypic effects of a bipolar liability gene among individuals with major depressive disorder

Variations in voltage-dependent calcium channel L-type, alpha 1C subunit (CACNA1C) gene have been associated with bipolar disorder in a recent meta-analysis of genome-wide association studies [Ferreira et al., 2008]. The impact of these variations on other psychiatric disorders has not been yet investigated. Caucasian non-Hispanic participants in the STAR*D study of treatment for depression for whom DNA was available (N = 1213) were genotyped at two single-nucleotide polymorphisms (SNPs) (rs10848635 and rs1006737) in the CACNA1C gene. We examined putative phenotypic indicators of bipolarity among patients with major depression and elements of longitudinal course suggestive of latent bipolarity. We also considered remission and depression severity following citalopram treatment. The rs10848635 risk allele was significantly associated with lower levels of baseline agitation (P = 0.03; beta = -0.09). The rs1006737 risk allele was significantly associated with lesser baseline depression severity (P = 0.04; beta = -0.4) and decreased likelihood of insomnia (P = 0.047; beta = -0.22). Both markers were associated with an increased risk of citalopram-emergent suicidality (rs10848635: OR = 1.29, P = 0.04; rs1006737: OR = 1.34, P = 0.02). In this exploratory analysis, treatment-emergent suicidality was associated with two risk alleles in a putative bipolar liability gene.

Accumulation of common polymorphisms is associated with development of hypertension: a 12-year follow-up from the Ohasama study

Hypertension is a complex multi-factorial and polygenic disorder. Nevertheless, most studies have focused on single-gene effects. Furthermore, a majority of these studies have been cross-sectional and diagnosed hypertension using conventional blood pressure (BP) measurements, which are known to be subject to biases, including the so-called white-coat effect. Thus, we performed a longitudinal association study to clarify the effects of polymorphism accumulation on the development of hypertension that is defined on the basis of self-measured BP at home (home BP). In 403 Japanese aged 40-79 years with home normotension (home BP <135/85 mm Hg, and not treated with antihypertensive medication at baseline), we examined the associations of 51 single-nucleotide polymorphisms (SNPs) classically nominated or reported to be associated with hypertension in the Japanese Millennium Genome Project for Hypertension with a 12-year risk of progression to home hypertension (home BP >or=135/85 mm Hg, or start of antihypertensive medication). Out of 51 SNPs, four significantly and independently predicted the risk of progression of home hypertension, even after adjustment for possible confounding factors, including baseline home BP value. These were rs3767489 near the regulator of G-protein signaling 2 (RGS2), rs4961 in adducin 1 (ADD1), rs2236957 in the calcium channel, voltage-dependent, alpha-2/delta-subunit 2 (CACNA2D2) and rs769214 in catalase (CAT). Accumulation of these SNPs significantly improved the predictive values for the development of home hypertension. In conclusion, this longitudinal study, which was based on home BP measurement, showed that accumulation of common polymorphisms reliably predicted the risk of future hypertension in the Japanese general population.

Pharmacogenetics of antihypertensive treatment: detailing disciplinary dissonance

Hypertension is a common condition associated with increased cardiovascular morbidity and mortality. In the USA only approximately a third of those who are aware of their hypertensive status successfully control their blood pressure. One reason for this is the unpredictable response individuals have to treatment. Clinicians must often rely on empirical methods to match patients with effective drug treatment. Hypertension pharmacogenetics seeks to find genetic predictors of response to drugs that lower blood pressure and to translate this knowledge into clinical practice. To date, around 60 studies have investigated associations between genetic polymorphisms and response to antihypertensive drugs. Here we review 18 studies that have been published since 2005. While consonant findings that are insufficient for clinical translation remain the norm, some consistent findings are emerging with several gene-treatment combinations. Nonetheless, differences in study designs, variable methods for assessing pharmacologic exposures, heterogeneous phenotypes (that is, response variables and outcomes ranging from blood pressure to clinical outcomes) and small sample sizes coupled with a short duration of follow-up in many studies account for a large portion of these inconsistencies. Progress in the future will depend upon our ability to launch large studies using high-fidelity phenotyping with multiple drugs and multiple ethnic groups.

CACNA1C gene polymorphisms, cardiovascular disease outcomes, and treatment response

BACKGROUND

The gene encoding the target of calcium channel blockers, the alpha1c-subunit of the L-type calcium channel (CACNA1C), has not been well characterized, and only small pharmacogenetic studies testing this gene have been published to date.

METHODS AND RESULTS

Resequencing of CACNA1C was performed followed by a nested case-control study of the INternational VErapamil SR/trandolapril STudy (INVEST) GENEtic Substudy (INVEST-GENES). Of 46 polymorphisms identified, 8 were assessed in the INVEST-GENES. Rs1051375 was found to have a significant interaction with treatment strategy (P=0.0001). Rs1051375 A/A genotype was associated with a 46% reduction in the primary outcome among those randomized to verapamil SR treatment, when compared with atenolol treatment (odds ratio 0.54 95% CI 0.32 to 0.92). In heterozygous A/G individuals, there was no difference in the occurrence of the primary outcome when randomized to verapamil SR versus atenolol treatment (odds ratio 1.47 95% CI 0.86 to 2.53), whereas homozygous G/G individuals had a greater than 4-fold increased risk of the primary outcome with verapamil treatment compared with those randomized to atenolol treatment (odds ratio 4.59 95% CI 1.67 to 12.67). We did not identify allelic expression imbalance or differences in mRNA expression in heart tissue by rs1051375 genotype.

CONCLUSIONS

Variation in CACNA1C is associated with treatment response among hypertensive patients with stable coronary artery disease. Our data suggest a genetically defined group of patients that benefit most from calcium channel blocker therapy, a group that benefits most from beta-blocker therapy, and a third group in which calcium channel blocker and beta-blocker therapy are equivalent.

Genetic polymorphisms of L-type calcium channel alpha1C and alpha1D subunit genes are associated with sensitivity to the antihypertensive effects of L-type dihydropyridine calcium-channel blockers

BACKGROUND

The response of blood pressure (BP) to L-type dihydropyridine calcium-channel blockers (dCCBs) differs among individuals.

METHODS AND RESULTS

A pharmacogenomic analysis was undertaken in 161 patients with essential hypertension who were treated with dCCBs to study whether genetic polymorphisms of the calcium channel alpha1C and alpha1D subunit genes, CACNA1C and CACNA1D, are associated with the antihypertensive effects of dCCBs. Responders were defined as those in whom systolic BP (SBP) was lowered by more than 20 mmHg or diastolic BP (DBP) was lowered by more than 10 mmHg after treatment with dCCBs. Eleven sequence-proven polymorphisms of CACNA1C and 5 common polymorphisms of CACNA1D chosen from a public database were subjected to genotypic analysis. The comparison of polymorphism prevalence between responders and nonresponders showed significant differences in CACNA1D rs312481G>A and rs3774426C>T, and in CACNA1C 527974G>A. There were significant differences in SBP or DBP between alleles in these single nucleotide polymorphisms (SNPs). A much more significant reduction in BP was observed for the combined presence of these SNPs.

CONCLUSIONS

Three SNPs in CACNA1D or CACNA1C are genetic polymorphisms conferring sensitivity to the antihypertensive effects of L-type dCCBs in patients with hypertension. The BP reduction by L-type dCCBs might be predicted by evaluating these polymorphisms.

Effects of CYP3A5, MDR1 and CACNA1C polymorphisms on the oral disposition and response of nimodipine in a Chinese cohort

PURPOSE

Our objective was to study the effects of polymorphic the CYP3A5 (allele *1 and *3), MDR1 [single nucleotide polymorphisms (SNPs) G2677T, C3435T] and CACNA1C (SNPs rs2239128, rs2239050, rs2238032) genes on nimodipine oral disposition and response in healthy Chinese subjects.

METHODS

Pharmacokinetics and pharmacodynamics data were obtained from a bioequivalence study, and the same 20 subjects were genotyped for CYP3A, MDR1 and CACNA1C. An additional 41 healthy Chinese subjects were recruited to obtain an indication of the distribution of CACNA1C polymorphisms in the Chinese population. Racial differences in the frequency of CACNA1C alleles were assessed. The phenotype differences between genotypes were analyzed.

RESULTS

The allelic frequencies of rs2239050 and rs2238032 in our Chinese cohort were different from those in a Caucasian population (p < 0.01). Subjects with mutant alleles (*3/*3) of the CYP3A5 gene had a decreased oral clearance of nimodipine, with a higher lnC(max) or 1n AUC(0-infinity) compared with those subjects with the heterozygote (*1/*3) or wild type (*1/*1) gene. The CACNA1C rs2239128 C and rs2239050 G SNPs were associated with a stronger efficacy compared with their respective alleles, rs2239128 T and rs2239050 C. MDR1 polymorphisms showed no significance in terms of nimodipine disposition.

CONCLUSIONS

The polymorphic CYP3A5 (allele *1 and *3) and CACNA1C genes have effects on nimodipine oral disposition and response in healthy Chinese subjects. The homozygous variant of CYP3A5 (*3/*3) was associated with significantly increased nimodipine exposure. CACNA1C SNPs rs2239128 C and rs2239050 G were associated with a stronger efficacy.

Bcl-2 antagonist apogossypol (NSC736630) displays single-agent activity in Bcl-2-transgenic mice and has superior efficacy with less toxicity compared with gossypol (NSC19048)

Altered expression of Bcl-2 family proteins plays central roles in apoptosis dysregulation in cancer and leukemia, promoting malignant cell expansion and contributing to chemoresistance. In this study, we compared the toxicity and efficacy in mice of natural product gossypol and its semisynthetic derivative apo-gossypol, compounds that bind and inhibit antiapoptotic Bcl-2 family proteins. Daily oral dosing studies showed that mice tolerate doses of apogossypol 2- to 4-times higher than gossypol. Hepatotoxicity and gastrointestinal toxicity represented the major adverse activities of gossypol, with apogossypol far less toxic. Efficacy was tested in transgenic mice in which Bcl-2 is overexpressed in B cells, resembling low-grade follicular lymphoma in humans. In vitro, Bcl-2-expressing B cells from transgenic mice were more sensitive to cytotoxicity induced by apogossypol than gossypol, with LD50 values of 3 to 5 microM and 7.5 to 10 microM, respectively. In vivo, using the maximum tolerated dose of gossypol for sequential daily dosing, apogossypol displayed superior activity to gossypol in terms of reducing splenomegaly and reducing B-cell counts in spleens of Bcl-2-transgenic mice. Taken together, these studies indicate that apogossypol is superior to parent compound gossypol with respect to toxicology and efficacy, suggesting that further development of this compound for cancer therapy is warranted.