Common genetic variants in the chromogranin A promoter alter autonomic activity and blood pressure. Kidney Int. 2008;74:115-125. [PMID: 18432188 DOI: 10.1038/ki.2008.113]

Age and Sex-related Chromogranin A Gene Polymorphisms and its Association with Metabolic Syndrome Components

Introduction

The purpose of this study was to determine the possible differences in genetic polymorphisms and serum levels of chromogranin A (CgA), according to age and sex, in subjects with and without metabolic syndrome (MetS).

Methodology

The genotyping and serum level of CgA and biochemical parameters were measured by the T-ARMS-PCR and PCR-RFLP and ELISA and spectrophotometer methods, respectively.

Results

A comparison of males with and without MetS showed significantly lower high-density lipoprotein-cholesterol (HDL-C) levels than those of females.At ages 30-70 years, both sexes showed significant differences in triglycerides (TG), fasting blood sugar (FBS), CgA levels and waist circumference (WC) when compared to the two groups. Both sexes with MetS indicated significant differences in systolic blood pressure (SBP) at ages 40-70 years, while at ages 40-59 years, there was a significant difference in HDL-C level in males.There was a significant correlation between serum levels of FBS, TG, SBP and WC (in both sexes), and CgA in subjects with MetS. Significant correlation was found between HDL-C level and diastolic blood pressure (DBP), and CgA level in males and females, respectively. CgA genotype frequency (T-415C and C+87T polymorphisms) showed no significant differences between males and females with and without MetS, while there was only a significant difference in frequency of the genotypes T-415C when compared to males with and without MetS.

Conclusion

The CgA appears to be strongly associated with MetS components in both sexes. Variation in CgA gene expression may affect the T-415C polymorphism in males. This may mean that the structure of CgA genetics differs in different ethnic groups. Differences in the serum level and expression of CgA gene may show valuable study results that it may be expected a relationship between these variables and the MetS.

Chromogranin A and its derived peptides: potential regulators of cholesterol homeostasis

Chromogranin A (CHGA), a member of the granin family of proteins, has been an attractive therapeutic target and candidate biomarker for several cardiovascular, neurological, and inflammatory disorders. The prominence of CHGA stems from the pleiotropic roles of several bioactive peptides (e.g., catestatin, pancreastatin, vasostatins) generated by its proteolytic cleavage and by their wide anatomical distribution. These peptides are emerging as novel modulators of cardiometabolic diseases that are often linked to high blood cholesterol levels. However, their impact on cholesterol homeostasis is poorly understood. The dynamic nature of cholesterol and its multitudinous roles in almost every aspect of normal body function makes it an integral component of metabolic physiology. A tightly regulated coordination of cholesterol homeostasis is imperative for proper functioning of cellular and metabolic processes. The deregulation of cholesterol levels can result in several pathophysiological states. Although studies till date suggest regulatory roles for CHGA and its derived peptides on cholesterol levels, the mechanisms by which this is achieved still remain unclear. This review aims to aggregate and consolidate the available evidence linking CHGA with cholesterol homeostasis in health and disease. In addition, we also look at common molecular regulatory factors (viz., transcription factors and microRNAs) which could govern the expression of CHGA and genes involved in cholesterol homeostasis under basal and pathological conditions. In order to gain further insights into the pathways mediating cholesterol regulation by CHGA/its derived peptides, a few prospective signaling pathways are explored, which could act as primers for future studies.

Chromogranin A pathway: from pathogenic molecule to renal disease

BACKGROUND

Chromogranin A (CHGA) is an index granin protein critical for biogenesis and exocytotic release of catecholamine storage granules. It is elevated in plasma of patients with sympathetic over-activity and kidney dysfunction. Several CHGA polymorphisms are associated with hypertensive kidney disease. Previously, we unraveled the molecular mechanism by which CHGA expression is regulated in African Americans carrying a genetic variation associated with hypertensive chronic kidney disease (CKD).

METHOD

Experimental CKD mouse model were created by 5/6th nephrectomy (Npx) using wild-type and Chga-/- knockout mouse strains to delineate the role of CHGA in CKD.

RESULT

Wild-type-Npx mice expressing Chga developed exacerbated azotemia and fibrosis as compared with their knockout-Npx counterparts. Gene expression profiling revealed downregulation of mitochondrial respiratory complexes genes consistent with maladaptive mitochondria in wild-type-Npx mice, contrasted to knockout-Npx. In healthy individuals, an inverse relationship between circulating CHGA levels and glomerular function was observed. In vitro, mesangial cells treated with CHGA-triggered nitric oxide release by a signaling mechanism involving scavenger receptor SR-A. The CHGA-treated and untreated mesangial cells displayed differential expression of cytokine, chemokine, complement, acute phase inflammatory and apoptotic pathway genes. Thus, build-up of plasma CHGA because of kidney injury served as an insult to the mesangial cells resulting in expression of genes promoting inflammation, fibrosis, and progression of CKD.

CONCLUSION

These findings improve understanding of the role of elevated CHGA in the progression of CKD and reveal novel pathways that could be exploited for therapeutic strategies in hypertensive kidney disease.

A haplotype variant of the human chromogranin A gene (CHGA) promoter increases CHGA expression and the risk for cardiometabolic disorders

The acidic glycoprotein chromogranin A (CHGA) is co-stored/co-secreted with catecholamines and crucial for secretory vesicle biogenesis in neuronal/neuroendocrine cells. CHGA is dysregulated in several cardiovascular diseases, but the underlying mechanisms are not well established. Here, we sought to identify common polymorphisms in the CHGA promoter and to explore the mechanistic basis of their plausible contribution to regulating CHGA protein levels in circulation. Resequencing of the CHGA promoter in an Indian population (n = 769) yielded nine single-nucleotide polymorphisms (SNPs): G-1106A, A-1018T, T-1014C, T-988G, G-513A, G-462A, T-415C, C-89A, and C-57T. Linkage disequilibrium (LD) analysis indicated strong LD among SNPs at the -1014, -988, -462, and -89 bp positions and between the -1018 and -57 bp positions. Haplotype analysis predicted five major promoter haplotypes that displayed differential promoter activities in neuronal cells; specifically, haplotype 2 (containing variant T alleles at -1018 and -57 bp) exhibited the highest promoter activity. Systematic computational and experimental analyses revealed that transcription factor c-Rel has a role in activating the CHGA promoter haplotype 2 under basal and pathophysiological conditions (viz. inflammation and hypoxia). Consistent with the higher in vitro CHGA promoter activity of haplotype 2, individuals carrying this haplotype had higher plasma CHGA levels, plasma glucose levels, diastolic blood pressure, and body mass index. In conclusion, these results suggest a functional role of the CHGA promoter haplotype 2 (occurring in a large proportion of the world population) in enhancing CHGA expression in haplotype 2 carriers who may be at higher risk for cardiovascular/metabolic disorders.

Correlation study on chromogranin A genetic polymorphism and prognosis of critically ill patients

OBJECTIVE

The objective was to investigate the correlation between single nucleotide polymorphism (SNP) of chromogranin A (CHGA) and prognosis of critically ill patients.

METHODS

We screened 357 critically ill patients consecutively admitted to our intensive care unit. The -89/-415/-462 SNP locus in the promoter region and the +9559/+9578/+9590/+9611 SNP locus in exon 7 coding of CHGA were genotyped by polymerase chain reaction and DNA sequencing technology. Subsequently, the correlation between genotype and prognosis of patients was analyzed.

RESULTS

(1) Three hundred critically ill Chinese Han patients were enrolled in the study. CHGA-415/-462/+9559/+9611 SNPs were polymorphically distributed. Phenotypes of the 4 SNPs were shown not to be in linkage disequilibrium, and there were no significant differences in the minor allele frequencies (MAFs) of the 4 SNPs between participants of this study and healthy people in Asia. (2) The CHGA-415 T/C MAF of the nonsurvival group was significantly higher than that of the survival group (MAF 0.3813 and 0.2864, respectively; P=.026). Survival analysis showed that there were significant differences between the CHGA-415 T/C mutation group (including TC and CC genotypes) and the wild-type group (TT genotype) (log rank=8.887, P=.003). The mortality in the mutant group was significantly higher than that in the wild-type group (0.3333 and 0.1852, respectively; P=.004). (3) Binary logistic analysis showed that CHGA-415 T/C polymorphism was an independent risk factor for the mortality of critically ill patients (odds ratio, 2.286; 95% confidence interval, 1.165-4.484; P=.016).

CONCLUSIONS

Critically ill patients with CHGA-415 T/C mutant genotype display higher 30-day mortality than those with the wild-type group. CHGA-415 T/C polymorphism is an independent risk factor of poor prognosis in critically ill Chinese Han patients.

Analysis and validation of traits associated with a single nucleotide polymorphism Gly364Ser in catestatin using humanized chromogranin A mouse models

OBJECTIVE

The human prohormone chromogranin A (CHGA), an index member of the granin family is processed to generate catestatin, a peptide that is hypotensive in action and modulates catecholamine release within the sympathoadrenal system. Hypertensive patients with excess sympathetic activity have diminished catestatin. Often the study of physiological consequences of human genetic variation is confounded by elements such as other variations in obligatory linkage disequilibrium with the variant being studied. Also the phenotype of the variant may be influenced by genetic background that varies amongst individuals. This study addresses the effects of a human catestatin polymorphism (rs9658667) using humanized CHGA mouse models.

METHODS

We created pertinent humanized mouse models wherein the mouse Chga gene locus was replaced by the human ortholog wild-type and the variant versions. This allowed for probing of the effects of catestatin variation in vivo with controls for other variations and global genetic background.

RESULTS

Both the wild-type and variant human catestatin expressing mouse models were normotensive. The variant catestatin mouse model recapitulated physiological influence of the polymorphism on autonomic traits. These mice had diminished catecholamine, attenuated stress response and increased baroreceptor slopes that would suggest reduced risk of developing hypertension. Elevated plasma glucose, a trait observed in humans was not observed in mice expressing the variant catestatin.

CONCLUSION

This functional genomics approach of creating humanized mouse models to study rs9658667 polymorphism recapitulated and validated many of the human trait associations. This approach can also be applied in the study of other human gene polymorphisms.

Roles of catecholamine related polymorphisms in hypertension

The objective of this review is to summarize current data obtained so far in catecholamine-essential hypertension (EH) relationships on a genetic basis. As the major elements driving the sympathetic system’s actions, catecholamines modulate a variety of physiological processes and mutations related to the system. This could generate serious disorders, such as severe mental illnesses, stress-induced disorders, or impaired control of blood pressure or motor pathways. EH is idiopathic, and the genetic basis of its causes and substantial interindividual discrepancies in response to different types of treatments are the focus of interest. Susceptibility to disease or efficacy of treatments are thought to reflect genomic variabilities among individuals. Therefore, outlining the available knowledge in functional genetic polymorphisms linked to EH will make the picture clearer and will help to establish future prospects in the field.

Adrenergic genetic mechanisms in hypertension and hypertensive kidney disease

Catecholamine secretory traits were significantly heritable, as were stress-induced blood pressure changes. Tyrosine hydroxylase (TH) is the rate-limiting enzyme in catecholamine biosynthesis. In the tyrosine hyroxylase promoter, significant associations were found for urinary catecholamine excretion and for blood pressure response to stress. TH promoter haplotype 2 (TGGG) showed pleiotropy, increasing both norepinephrine excretion and blood pressure during stress. In hypertension, 2 independent case-control studies (1,266 subjects with 53% women and 927 subjects with 24% women) replicated the effect of C-824T in the determination of blood pressure. Chromogranin A (CHGA) plays a fundamental role in the biogenesis of catecholamine secretory granules. Changes in the storage and release of CHGA in clinical and experimental hypertension prompted us to study whether genetic variation at the CHGA locus might contribute to alterations in autonomic function, and hence hypertension and its target organ consequences such as hypertensive kidney disease (nephrosclerosis). Systematic polymorphism discovery across the human CHGA locus revealed such regulatory regions as the proximal promoter and 3'-UTR. In chromaffin cell-transfected CHGA 3'-UTR and promoter/luciferase reporter plasmids, the functional consequences of the regulatory/non-coding allelic variants were documented. Variants in both the proximal promoter and the 3'-UTR displayed statistical associations with hypertension and hypertensive end stage renal disease. Therefore, I would like to review the common genetic variation in TH and CHGA as a cause of inter-individual variation in sympathetic activity, and ultimately blood pressure and hypertensive kidney disease.

MicroRNA-22 and promoter motif polymorphisms at the Chga locus in genetic hypertension: functional and therapeutic implications for gene expression and the pathogenesis of hypertension

Hypertension is a common hereditary syndrome with unclear pathogenesis. Chromogranin A (Chga), which catalyzes formation and cargo storage of regulated secretory granules in neuroendocrine cells, contributes to blood pressure homeostasis centrally and peripherally. Elevated Chga occurs in spontaneously hypertensive rat (SHR) adrenal glands and plasma, but central expression is unexplored. In this report, we measured SHR and Wistar-Kyoto rat (control) Chga expression in central and peripheral nervous systems, and found Chga protein to be decreased in the SHR brainstem, yet increased in the adrenal and the plasma. By re-sequencing, we systematically identified five promoter, two coding and one 3'-untranslated region (3'-UTR) polymorphism at the SHR (versus WKY or BN) Chga locus. Using HXB/BXH recombinant inbred (RI) strain linkage and correlations, we demonstrated genetic determination of Chga expression in SHR, including a cis-quantitative trait loci (QTLs) (i.e. at the Chga locus), and such expression influenced biochemical determinants of blood pressure, including a cascade of catecholamine biosynthetic enzymes, catecholamines themselves and steroids. Luciferase reporter assays demonstrated that the 3'-UTR polymorphism (which disrupts a microRNA miR-22 motif) and promoter polymorphisms altered gene expression consistent with the decline in SHR central Chga expression. Coding region polymorphisms did not account for changes in Chga expression or function. Thus, we hypothesized that the 3'-UTR and promoter mutations lead to dysregulation (diminution) of Chga in brainstem cardiovascular control nuclei, ultimately contributing to the pathogenesis of hypertension in SHR. Accordingly, we demonstrated that in vivo administration of miR-22 antagomir to SHR causes substantial (∼18 mmHg) reductions in blood pressure, opening a novel therapeutic avenue for hypertension.

Single nucleotide polymorphism in gene encoding transcription factor Prep1 is associated with HIV-1-associated dementia

Background

Infection with HIV-1 may result in severe cognitive and motor impairment, referred to as HIV-1-associated dementia (HAD). While its prevalence has dropped significantly in the era of combination antiretroviral therapy, milder neurocognitive disorders persist with a high prevalence. To identify additional therapeutic targets for treating HIV-associated neurocognitive disorders, several candidate gene polymorphisms have been evaluated, but few have been replicated across multiple studies.

Methods

We here tested 7 candidate gene polymorphisms for association with HAD in a case-control study consisting of 86 HAD cases and 246 non-HAD AIDS patients as controls. Since infected monocytes and macrophages are thought to play an important role in the infection of the brain, 5 recently identified single nucleotide polymorphisms (SNPs) affecting HIV-1 replication in macrophages in vitro were also tested.

Results

The CCR5 wt/Δ32 genotype was only associated with HAD in individuals who developed AIDS prior to 1991, in agreement with the observed fading effect of this genotype on viral load set point. A significant difference in genotype distribution among all cases and controls irrespective of year of AIDS diagnosis was found only for a SNP in candidate gene PREP1 (p = 1.2×10⁻⁵). Prep1 has recently been identified as a transcription factor preferentially binding the −2,518 G allele in the promoter of the gene encoding MCP-1, a protein with a well established role in the etiology of HAD.

Conclusion

These results support previous findings suggesting an important role for MCP-1 in the onset of HIV-1-associated neurocognitive disorders.

Genetic variation within a metabolic motif in the chromogranin a promoter: pleiotropic influence on cardiometabolic risk traits in twins

BACKGROUND

The cardiometabolic syndrome comprised of multiple correlated traits, but its origin is incompletely understood. Chromogranin A (CHGA) is required for formation of the catecholamine secretory pathway in sympathochromaffin cells. In twin pair studies, we found that CHGA traits aggregated with body mass index (BMI), as well as its biochemical determinant leptin. METHODS Here we used the twin method to probe the role of heredity in generating such risk traits, and then investigated the role of risk-trait-associated CHGA promoter genetic variation in transfected chromaffin cells. Trait heritability (h(2)) and shared genetic determination among traits (pleiotropy, genetic covariance, ρ(G)) were estimated by variance components in twin pairs.

RESULTS

CHGA, BMI, and leptin each displayed substantial h(2), and the traits also aggregated with several features of the metabolic syndrome (e.g., insulin resistance, blood pressure (BP), hypertension, catecholamines, and C-reactive protein (CRP)). Twin studies demonstrated genetic covariance (pleiotropy, ρ(G)) for CHGA, BMI, and leptin with other metabolic traits (insulin resistance, BP, and CRP). We therefore investigated the CHGA locus for mechanisms of codetermination with such metabolic traits. A common functional variant in the human CHGA promoter (G-462A, rs9658634, minor allele frequency ~21%) was associated with leptin and CRP secretion, as well as BMI, especially in women; marker-on-trait effects on BMI were replicated across twin populations on two continents. In CHGA promoter/luciferase reporter plasmids transfected into chromaffin cells, G-462A alleles differed markedly in reporter expression. The G-462A variant disrupted predicted transcriptional control by a PPARγ/RXRα motif and costimulation by PPARγ/RXRα and their cognate ligands, differentially activated the two alleles. During chromatin immunoprecipitation, endogenous PPARγ bound the motif.

CONCLUSIONS

Multiple features of the metabolic syndrome are thus under joint (pleiotropic) genetic determination, with CHGA as one such contributory locus: a common polymorphism in the promoter (G-462A) of CHGA predicts such heritable metabolic traits as BMI and leptin. CHGA promoter variant G-462A was not only associated with such metabolic traits but also disrupted a PPARγ/RXRα motif and responded differentially to characteristic trans-activators of that motif. The results suggest novel links between the catecholaminergic system and risk for the metabolic syndrome as well as systemic hypertension.

The extended granin family: structure, function, and biomedical implications

The chromogranins (chromogranin A and chromogranin B), secretogranins (secretogranin II and secretogranin III), and additional related proteins (7B2, NESP55, proSAAS, and VGF) that together comprise the granin family subserve essential roles in the regulated secretory pathway that is responsible for controlled delivery of peptides, hormones, neurotransmitters, and growth factors. Here we review the structure and function of granins and granin-derived peptides and expansive new genetic evidence, including recent single-nucleotide polymorphism mapping, genomic sequence comparisons, and analysis of transgenic and knockout mice, which together support an important and evolutionarily conserved role for these proteins in large dense-core vesicle biogenesis and regulated secretion. Recent data further indicate that their processed peptides function prominently in metabolic and glucose homeostasis, emotional behavior, pain pathways, and blood pressure modulation, suggesting future utility of granins and granin-derived peptides as novel disease biomarkers.

Contemporary approaches to genetic influences on hypertension

PURPOSE OF REVIEW

Essential hypertension has long been considered to be primarily 'genetic,' though recent studies have only revealed minor contributions to blood pressure. Technology has advanced tremendously in the recent years, with much focus on DNA studies utilizing both candidate gene and genome-wide association studies. However, many new areas that need continued investigation have arisen.

RECENT FINDINGS

In addition to DNA studies, genetic studies are actively pursuing previously unexplored areas of potential variation, such as that which occurs posttranscriptionally in RNA and posttranslationally in protein structure. Advances have also been made in animal models and systems biology for large-scale integrative approaches. However, many other areas need continued investigation in the genetics of hypertension, including improved phenotyping and trait definition, gene-by-gene interactions (epistasis), and gene-by-environment interactions. 'Next generation' sequencing will assist researchers in performing more extensive genetic studies even more quickly, especially on unusual (rare) genetic variants.

SUMMARY

Hypertension appears to have many genetic contributions from each regulatory area ranging from DNA to RNA to protein to postprotein to interactive influences of the environment on genes. New technologies have enabled such research to advance in the recent years. However, for this complex trait of hypertension, continued efforts must progress in all of these areas as well as in increased modeling and sequencing, so that the knowledge may be united for a comprehensive understanding of this common disease, such that diagnosis and treatment options in hypertensive patients and those at risk are facilitated.

Proteomic analysis yields an unexpected trans-acting point in control of the human sympathochromaffin phenotype

BACKGROUND

The secretory protein chromogranin A (CHGA) plays a necessary role in formation of catecholamine storage vesicles and gives rise to a catecholamine release-inhibitory fragment. Because genetic variation in the proximal human CHGA promoter predicts autonomic function and blood pressure, we explored how a common genetic variant alters transcription of the gene.

METHODS AND RESULTS

Bioinformatic analysis suggested that the common G-462A promoter variant (rs9658634) may disrupt as many as 3 transcriptional control motifs: LEF1, COUP-TF, and PPARγ-RXRα. During electrophoretic mobility shifts, chromaffin cell nuclear proteins bound specifically to the A (though not G) allele of CHGA promoter G-462A. On oligonucleotide affinity chromatography followed by electrospray ionization followed by 2-dimensional (tandem) mass spectrometry analysis of A allele eluates, the transcription factor LEF1 (lymphoid enhancer-binding factor-1) was identified. Interaction of LEF1 with the A allele at G-462A was confirmed by supershift. On cotransfection, LEF1 discriminated between the allelic variants, especially in chromaffin cells. Allele specificity of trans-activation by LEF1 was transferable to an isolated G-462A element fused to a heterologous (SV40) promoter. Because β-catenin (CTNNB1) can heterodimerize with LEF1, we tested the effect of cotransfection of this factor and again found A allele-specific perturbation of CHGA transcription.

CONCLUSIONS

Common genetic variation within the human CHGA promoter alters the interaction of specific factors in trans with the promoter, with LEF1 identified by proteomic analysis and confirmed by supershift. Coexpression experiments show functional effects of LEF1 and CTNNB1 on CHGA promoter. The findings document a novel role for components of the immune and WNT pathways in control of human sympathochromaffin phenotypes.

Naturally occurring genetic variants in human chromogranin A (CHGA) associated with hypertension as well as hypertensive renal disease

Chromogranin A (CHGA) plays a fundamental role in the biogenesis of catecholamine secretory granules. Changes in storage and release of CHGA in clinical and experimental hypertension prompted us to study whether genetic variation at the CHGA locus might contribute to alterations in autonomic function, and hence hypertension and its target organ consequences such as hypertensive renal disease (nephrosclerosis). Systematic polymorphism discovery across the human CHGA locus revealed both common and unusual variants in both the open reading frame and such regulatory regions as the proximal promoter and 30-UTR. In chromaffin cell-transfected CHGA 30-UTR and promoter/luciferase reporter plasmids, the functional consequences of the regulatory/non-coding allelic variants were documented. Variants in both the proximal promoter and the 30-UTR displayed statistical associations with hypertension. Genetic variation in the proximal CHGA promoter predicted glomerular filtration rate in healthy twins. However, for hypertensive renal damage, both end-stage renal disease and rate of progression of earlier disease were best predicted by variants in the 30-UTR. Finally, mechanistic studies were undertaken initiated by the clue that CHGA promoter variation predicted circulating endothelin-1. In cultured endothelial cells, CHGA triggered co-release of not only the vasoconstrictor and pro-fibrotic endothelin-1, but also the pro-coagulant von Willebrand Factor and the pro-angiogenic angiopoietin-2. These findings, coupled with stimulation of endothelin-1 release from glomerular capillary endothelial cells by CHGA, suggest a plausible mechanism whereby genetic variation at the CHGA locus eventuates in alterations in human renal function. These results document the consequences of genetic variation at the CHGA locus for cardiorenal disease and suggest mechanisms whereby such variation achieves functional effects.

Catecholamine storage vesicles: role of core protein genetic polymorphisms in hypertension

Hypertension is a complex trait with deranged autonomic control of the circulation. The sympathoadrenal system exerts minute-to-minute control over cardiac output and vascular tone. Catecholamine storage vesicles (or chromaffin granules) of the adrenal medulla contain remarkably high concentrations of chromogranins/secretogranins (or "granins"), catecholamines, neuropeptide Y, adenosine triphosphate (ATP), and Ca(2+). Within secretory granules, granins are co-stored with catecholamine neurotransmitters and co-released upon stimulation of the regulated secretory pathway. The principal granin family members, chromogranin A (CHGA), chromogranin B (CHGB), and secretogranin II (SCG2), may have evolved from shared ancestral exons by gene duplication. This article reviews human genetic variation at loci encoding the major granins and probes the effects of such polymorphisms on blood pressure, using twin pairs to probe heritability and individuals with the most extreme blood pressure values in the population to study hypertension.

Role of reactive oxygen species in hyperadrenergic hypertension: biochemical, physiological, and pharmacological evidence from targeted ablation of the chromogranin a (Chga) gene

BACKGROUND

Oxidative stress, an excessive production of reactive oxygen species (ROS) outstripping antioxidant defense mechanisms, occurs in cardiovascular pathologies, including hypertension. In the present study, we used biochemical, physiological, and pharmacological approaches to explore the role of derangements of catecholamines, ROS, and the endothelium-derived relaxing factor nitric oxide (NO(•)) in the development of a hyperadrenergic model of hereditary hypertension: targeted ablation (knockout [KO]) of chromogranin A (Chga) in the mouse.

METHODS AND RESULTS

Homozygous ⁻(/)⁻ Chga gene knockout (KO) mice were compared with wild-type (WT, +/+) control mice. In the KO mouse, elevations of systolic and diastolic blood pressure were accompanied by not only elevated catecholamine (norepinephrine and epinephrine) concentrations but also increased ROS (H₂O₂) and isoprostane (an index of lipid peroxidation), as well as depletion of NO(•). Renal transcript analyses implicated changes in Nox1/2, Xo/Xdh, and Sod1,2 mRNAs in ROS elevation by the KO state. KO alterations in blood pressure, catecholamines, H₂O₂, isoprostane, and NO(•) could be abrogated or even normalized (rescued) by either sympathetic outflow inhibition (with clonidine) or NADPH oxidase inhibition (with apocynin). In cultured renal podocytes, H₂O₂ production was substantially augmented by epinephrine (probably through β₂-adrenergic receptors) and modestly diminished by norepinephrine (probably through α₁-adrenergic receptors).

CONCLUSIONS

ROS appear to play a necessary role in the development of hyperadrenergic hypertension in this model, in a process mechanistically linking elevated blood pressure with catecholamine excess, renal transcriptional responses, ROS elevation, lipid peroxidation, and NO(•) depletion. Some of the changes appear to be dependent on transcription, whereas others are immediate. The cycle could be disrupted by inhibition of either sympathetic outflow or NADPH oxidase. Because common genetic variation at the human CHGA locus alters BP, the results have implications for antihypertensive treatment as well as prevention of target-organ consequences of the disease. The results document novel pathophysiological links between the adrenergic system and oxidative stress and suggest new strategies to probe the role and actions of ROS within this setting.

Clinical significance of polymorphism and expression of chromogranin a and endothelin-1 in prostate cancer

PURPOSE

We investigated the clinical significance of chromogranin A and endothelin-1 polymorphism and expression in prostate cancer.

MATERIALS AND METHODS

We analyzed 2 CHGA polymorphisms by polymerase chain reaction-restriction fragment length polymorphism in DNA samples of 435 patients with prostate cancer and 316 age matched male controls. Chromogranin A and endothelin-1 expression was evaluated by immunohistochemistry in prostate specimens of 114 men with prostate cancer who underwent radical retropubic prostatectomy and in 27 with bladder cancer who underwent radical cystectomy and served as controls.

RESULTS

For the CHGA Glu264Asp polymorphism men with the GG genotype were at 2.05 times higher risk for prostate cancer than men with the CC genotype (p = 0.014). In men with prostate cancer higher chromogranin A immunohistochemistry grade was associated with higher stage and higher Gleason score (p = 0.011 and 0.044, respectively). Multivariate analysis showed that chromogranin A immunohistochemistry grade was an independent variable for predicting biochemical failure after radical prostatectomy (p = 0.023). Higher endothelin-1 expression was observed in prostate cancers (p = 0.011), especially those with a higher Gleason score (p = 0.042). There was no significant relationship between chromogranin A polymorphisms, and chromogranin A and endothelin-1 expression.

CONCLUSIONS

Polymorphism and expression of chromogranin A and endothelin-1 have clinical significance in prostate cancer. Chromogranin A expression was an independent predictor of biochemical failure after prostatectomy in patients with localized prostate cancer.

Chromogranin a and the autonomic system: decomposition of heart rate variability and rescue by its catestatin fragment

Chromogranin A (CHGA/Chga) has been implicated in the genesis of systemic hypertension and consequent cardiac abnormalities. Catestatin (CST) (human CHGA(352-372)) replacement reduces blood pressure elevation and increases baroreflex sensitivity in Chga knockout (KO) mice. Because of the dampened baroreflex sensitivity, we reasoned that KO mice would display altered heart rate variability (HRV). Thus, we evaluated beat-to-beat measurements in HRV in wild-type (WT) and KO mice, before and after CST replacement. HR dynamics were evaluated by bipolar Einthoven electrocardiogram, with deconvolution into time and frequency domains, as well as Lorenz nonlinear return analyses. At baseline, HR was higher [444 +/- 24 beats per minute (bpm)] in KO compared with WT (330 +/- 18 bpm) mice. The total power in the HRV spectra was substantially diminished in KO animals. CST increased total power but only in KO mice. Each time-domain parameter was substantially lower in KO compared with WT mice, and the CST in the KO group could reverse the differences. Lorenz analysis revealed reductions in S1 (short axis perpendicular to the line of identity in the ellipse) and S2 (long axis along the line of identity in the ellipse) in KO animals, indicating that regulation of HRV is diminished in the parasympathetic and sympathetic domains. CST replacement caused restoration of both S1 and S2, in the KO group. These data suggest that Chga has a profound effect on autonomic tone to the heart and that its CST fragment is responsible for such actions. The results suggest future strategies for intervention in cardiovascular disorders accompanied by adverse HRV profiles.

Conserved regulatory motifs at phenylethanolamine N-methyltransferase (PNMT) are disrupted by common functional genetic variation: an integrated computational/experimental approach

The adrenomedullary hormone epinephrine transduces environmental stressors into cardiovascular events (tachycardia and hypertension). Although the epinephrine biosynthetic enzyme PNMT genetic locus displays both linkage and association to such traits, genetic variation underlying these quantitative phenotypes is not established. Using an integrated suite of computational and experimental approaches, we elucidate a functional mechanism for common (minor allele frequencies > 30%) genetic variants at PNMT. Transcription factor binding motif prediction on mammalian PNMT promoter alignments identified two variant regulatory motifs, SP1 and EGR1, disrupted by G-367A (rs3764351), and SOX17 motif created by G-161A (rs876493). Electrophoretic mobility shifts of approximately 30-bp oligonucleotides containing ancestral versus variant alleles validated the computational hypothesis. Queried against chromaffin cell nuclear protein extracts, only the G-367 and -161A alleles shifted. Specific antibodies applied in electrophoretic gel shift experiments confirmed binding of SP1 and EGR1 to G-367 and SOX17 to -161A. The in vitro allele-specific binding was verified in cella through promoter reporter assays: lower activity for -367A haplotypes cotransfected by SP1 (p = 0.002) and EGR1 (p = 0.034); and enhanced inhibition of -161A haplotypes (p = 0.0003) cotransfected with SP1 + SOX17. Finally, we probed cis/trans regulation with endogenous factors by chromatin immunoprecipitation using SP1/EGR1/SOX17 antibodies. We describe the systematic application of complementary computational and experimental techniques to detect and document functional genetic variation in a trait-associated regulatory region. The results provide insight into cis and trans transcriptional mechanisms whereby common variation at PNMT can give rise to quantitative changes in human physiological and disease traits. Thus, PNMT variants in cis may interact with nuclear factors in trans to govern adrenergic activity.

Chromogranin A: a novel susceptibility gene for essential hypertension

Chromogranin A (CHGA) is ubiquitously expressed in secretory cells of the endocrine, neuroendocrine, and neuronal tissues. Although this protein has long been known as a marker for neuroendocrine tumors, its role in cardiovascular disease states including essential hypertension (EH) has only recently been recognized. It acts as a prohormone giving rise to bioactive peptides such as vasostatin-I (human CHGA(1-76)) and catestatin (human CHGA(352-372)) that exhibit several cardiovascular regulatory functions. CHGA is over-expressed but catestatin is diminished in EH. Moreover, genetic variants in the promoter, catestatin, and 3'-untranslated regions of the human CHGA gene alter autonomic activity and blood pressure. Consistent with these findings, targeted ablation of this gene causes severe arterial hypertension and ventricular hypertrophy in mice. Transgenic expression of the human CHGA gene or exogenous administration of catestatin restores blood pressure in these mice. Thus, the accumulated evidence establishes CHGA as a novel susceptibility gene for EH.

Long human CHGA flanking chromosome 14 sequence required for optimal BAC transgenic "rescue" of disease phenotypes in the mouse Chga knockout

Chromogranin A (CHGA) plays a catalytic role in formation of catecholamine storage vesicles and also serves as precursor to the peptide fragment catestatin, a catecholamine secretory inhibitor whose expression is diminished in the hypertensive individuals. We previously reported the hypertensive, hyperadrenergic phenotype of Chga-/- knockout (KO) mice and rescue by the human ortholog. In the present study, we compare two humanized CHGA mouse models. Into the Chga null background, by bacterial artificial chromosome transgenesis human CHGA transgene has been introduced. Both lines have the complete approximately 12 kbp CHGA gene integrated stably in the genome but have substantial differences in CHGA expression, as well as consequent sympathochromaffin biochemistry and physiology. A mouse model with longer-insert HumCHGA31 displays integration encompassing not only CHGA but also long human flanking sequences. This is in contrast to mouse model HumCHGA19 with limited flanking human sequence co-integrated. As a consequence, HumCHGA19 mice have normal though diminished pattern of spatial expression of CHGA, and 14-fold lower circulating CHGA, with failure to rescue KO phenotypes to normalcy. In the longer-insert HumCHGA31 mice, catecholamine secretion, exaggerated responses to environmental stress, and hypertension were all alleviated. Promoter regions of the transgenes in both HumCHGA19 and HumCHGA31 display minimal CpG methylation, weighing against differential "position effects" of integration, and thus suggesting that lack of cis elements required for optimal CHGA expression occurs in HumCHGA19 mice. Such "humanized" CHGA mouse models may be useful in probing the physiological consequences of variation in CHGA expression found in humans, with consequences for susceptibility to hypertension and cardiovascular disease.

Global metabolic consequences of the chromogranin A-null model of hypertension: transcriptomic detection, pathway identification, and experimental verification

Chromogranin A (CHGA) has a crucial role in formation of regulated secretory granules in neuroendocrine tissues and is also a prohormone that is proteolytically processed into peptides with diverse and complex actions. CHGA and several of its peptide products, including catestatin and pancreastatin, are implicated in pathogenesis of essential hypertension, insulin resistance, and the metabolic syndrome. The Chga knockout mouse (Chga KO) displays severe hypertension coupled with reduction in size, number, and density of regulated secretory granules. We performed genome-wide transcriptome profiling in Chga KO adrenal gland and liver for insight into biochemical and physiological systems altered in this monogenic mouse model of hypertension. Adrenal gene expression pathway prediction of enhanced insulin sensitivity (P = 0.03) in Chga KO was confirmed with glucose, insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) measurements: blood glucose was normal in Chga KO, blood insulin was reduced 4.5-fold (P < 0.0001), and HOMA-IR was decreased 3.8-fold (P < 0.002). Remarkably, such observations conclusively dissociate fundamental features of the metabolic syndrome in this monogenic hypertension model. Exogenous pancreastatin treatment restored insulin sensitivity in the Chga KO to near-normal levels. Gene expression predictions of decreased adrenal cholesterol biosynthesis (P < 0.001) and increased hepatic cholesterol biosynthesis (P < 0.001) were verified with tissue total cholesterol assays: Chga KO adrenal cholesterol decreased 1.8-fold (P = 0.039) and hepatic cholesterol increased 1.8-fold (P = 0.018). Transcriptional regulatory network prediction identified sets of transcription factors that may provide insight into the unclear mechanistic links among CHGA, cholesterol, insulin sensitivity, and the metabolic syndrome. These experiments demonstrate, for the first time, that genetic variation at the CHGA locus impacts insulin sensitivity and tissue cholesterol levels in an intact, living organism. The Chga KO may constitute a unique model for studying the relationship between the CHGA locus and disease phenotypes of the metabolic syndrome.

Chromogranin A regulates renal function by triggering Weibel-Palade body exocytosis

Chromogranin A (CHGA), a protein released from secretory granules of chromaffin cells and sympathetic nerves, triggers endothelin-1 release from endothelial cells. CHGA polymorphisms associate with an increased risk for ESRD, but whether altered CHGA-endothelium interactions may explain this association is unknown. Here, CHGA led to the release of endothelin-1 and Weibel-Palade body exocytosis in cultured human umbilical vein endothelial cells. In addition, CHGA triggered secretion of endothelin-1 from glomerular endothelial cells and TGF-beta1 from mesangial cells cocultured with glomerular endothelial cells. In humans, plasma CHGA correlated positively with endothelin-1 and negatively with GFR. GFR was highly heritable in twin pairs, and common promoter haplotypes of CHGA predicted GFR. In patients with progressive hypertensive renal disease, a CHGA haplotype predicted rate of GFR decline. In conclusion, these data suggest that CHGA acts through the glomerular endothelium to regulate renal function.