What is in your pantry? Entomologic anaphylaxis.

Background: The booklouse, Liposcelis bostrychophila, is a potent environmental allergen clinically associated with rhinoconjunctivitis and asthma. Despite its known infestation of grain products, anaphylaxis from ingestion of this organism has, to our knowledge, not been previously reported. We present the case of a 44-year-old woman who developed anaphylaxis to ingested oats and rice shown to be contaminated with L. bostrychophila. Objective: The objective was to isolate a distinct antigen from L. bostrychophila implicated in a case of unexplained anaphylaxis. Methods: In vitro studies were obtained for relevant ingested materials and aeroallergens. Skin-prick testing (SPT) was performed with standard extracts, contaminated oats, fresh oats, and crushed L. bostrychophila. Western blots were conducted using subject and control serum to detect specific immunoglobulin E (IgE) against the grains and L. bostrychophila extract. Competitive inhibition immunoblotting was used to assess specificity of IgE binding. Results: In vitro studies and SPT were notable for positive responses to dust mite and flour contaminated by L. bostrychophila, along with contaminated oats. Testing results for fresh oat and rice were negative. Immunoblots that used the subject's serum revealed a strongly positive band in the contaminated oat and rice extracts at 24 kD, whereas dust-mite extract yielded a single 14-kD band. Isolated L. bostrychophila extract also yielded a 24-kD band. Competitive inhibition experiments demonstrated that the 24-kD band in the contaminated oat extract was immunologically distinct from the 14-kD dust-mite band. Conclusion: Our case highlights the importance of considering L. bostrychophila as a potential culprit for unexplained anaphylaxis due to ingested grain products. Given the ubiquitous presence of this insect, we suspect that this may be a more common problem than previously recognized.

Identification of novel loci affecting circulating chromogranins and related peptides.

Chromogranins are pro-hormone secretory proteins released from neuroendocrine cells, with effects on control of blood pressure. We conducted a genome-wide association study for plasma catestatin, the catecholamine release inhibitory peptide derived from chromogranin A (CHGA), and other CHGA- or chromogranin B (CHGB)-related peptides, in 545 US and 1252 Australian subjects. This identified loci on chromosomes 4q35 and 5q34 affecting catestatin concentration (P = 3.40 × 10-30 for rs4253311 and 1.85 × 10-19 for rs2731672, respectively). Genes in these regions include the proteolytic enzymes kallikrein (KLKB1) and Factor XII (F12). In chromaffin cells, CHGA and KLKB1 proteins co-localized in catecholamine storage granules. In vitro, kallikrein cleaved recombinant human CHGA to catestatin, verified by mass spectrometry. The peptide identified from this digestion (CHGA360-373) selectively inhibited nicotinic cholinergic stimulated catecholamine release from chromaffin cells. A proteolytic cascade involving kallikrein and Factor XII cleaves chromogranins to active compounds both in vivo and in vitro.

Catestatin regulates vesicular quanta through modulation of cholinergic and peptidergic (PACAPergic) stimulation in PC12 cells.

We have previously shown that the chromogranin A (CgA)-derived peptide catestatin (CST: hCgA352-372) inhibits nicotine-induced secretion of catecholamines from the adrenal medulla and chromaffin cells. In the present study, we seek to determine whether CST regulates dense core (DC) vesicle (DCV) quanta (catecholamine and chromogranin/secretogranin proteins) during acute (0.5-h treatment) or chronic (24-h treatment) cholinergic (nicotine) or peptidergic (PACAP, pituitary adenylyl cyclase activating polypeptide) stimulation of PC12 cells. In acute experiments, we found that both nicotine (60 µM) and PACAP (0.1 µM) decreased intracellular norepinephrine (NE) content and increased 3H-NE secretion, with both effects markedly inhibited by co-treatment with CST (2 µM). In chronic experiments, we found that nicotine and PACAP both reduced DCV and DC diameters and that this effect was likewise prevented by CST. Nicotine or CST alone increased expression of CgA protein and together elicited an additional increase in CgA protein, implying that nicotine and CST utilize separate signaling pathways to activate CgA expression. In contrast, PACAP increased expression of CgB and SgII proteins, with a further potentiation by CST. CST augmented the expression of tyrosine hydroxylase (TH) but did not increase intracellular NE levels, presumably due to its inability to cause post-translational activation of TH through serine phosphorylation. Co-treatment of CST with nicotine or PACAP increased quantal size, plausibly due to increased synthesis of CgA, CgB and SgII by CST. We conclude that CST regulates DCV quanta by acutely inhibiting catecholamine secretion and chronically increasing expression of CgA after nicotinic stimulation and CgB and SgII after PACAPergic stimulation.

The catecholamine biosynthetic enzyme dopamine ß-hydroxylase (DBH): first genome-wide search positions trait-determining variants acting additively in the proximal promoter.

Dopamine beta-hydroxylase (DBH) is the biosynthetic enzyme catalyzing formation of norepinephrine. Changes in DBH expression or activity have been implicated in the pathogenesis of cardiovascular and neuropsychiatric disorders. Genetic determination of DBH enzymatic activity and its secretion are only incompletely understood. We began with a genome-wide association search for loci contributing to DBH activity in human plasma. Initially, in a population sample of European ancestry, we identified the proximal DBH promoter as a region harboring three common trait-determining variants (top hit rs1611115, P = 7.2 × 10(-51)). We confirmed their effects on transcription and showed that the three variants each acted additively on gene expression. Results were replicated in a population sample of Native American descent (top hit rs1611115, P = 4.1 × 10(-15)). Jointly, DBH variants accounted for 57% of DBH trait variation. We further identified a genome-wide significant SNP at the LOC338797 locus on chromosome 12 as trans-quantitative trait locus (QTL) (rs4255618, P = 4.62 × 10(-8)). Conditional analyses on DBH identified a third genomic region contributing to DBH variation: a likely cis-QTL adjacent to DBH in SARDH (rs7040170, P = 1.31 × 10(-14)) on chromosome 9q. We conclude that three common SNPs in the DBH promoter act additively to control phenotypic variation in DBH levels, and that two additional novel loci (SARDH and LOC338797) may also contribute to the expression of this catecholamine biosynthetic trait. Identification of DBH variants with strong effects makes it possible to take advantage of Mendelian randomization approaches to test causal effects of this intermediate trait on disease.

Polymorphisms at the F12 and KLKB1 loci have significant trait association with activation of the renin-angiotensin system.

BACKGROUND: Plasma coagulation Factor XIIa (Hageman factor; encoded by F12) and kallikrein (KAL or Fletcher factor; encoded by KLKB1) are proteases of the kallikerin-kinin system involved in converting the inactive circulating prorenin to renin. Renin is a key enzyme in the formation of angiotensin II, which regulates blood pressure, fluid and electrolyte balance and is a biomarker for cardiovascular, metabolic and renal function. The renin-angiotensin system is implicated in extinction learning in posttraumatic stress disorder. METHODS & RESULTS: Active plasma renin was measured from two independent cohorts- civilian twins and siblings, as well as U.S. Marines, for a total of 1,180 subjects. Genotyping these subjects revealed that the carriers of the minor alleles at the two loci- F12 and KLKB1 had a significant association with reduced levels of active plasma renin. Meta-analyses confirmed the association across cohorts. In vitro studies verified digestion of human recombinant pro-renin by kallikrein (KAL) to generate active renin. Subsequently, the active renin was able to digest the synthetic substrate angiotensinogen to angiotensin-I. Examination of mouse juxtaglomerular cell line and mouse kidney sections showed co-localization of KAL with renin. Expression of either REN or KLKB1 was regulated in cell line and rodent models of hypertension in response to oxidative stress, interleukin or arterial blood pressure changes. CONCLUSIONS: The functional variants of KLKB1 (rs3733402) and F12 (rs1801020) disrupted the cascade of enzymatic events, resulting in diminished formation of active renin. Using genetic, cellular and molecular approaches we found that conversion of zymogen prorenin to renin was influenced by these polymorphisms. The study suggests that the variant version of protease factor XIIa due to the amino acid substitution had reduced ability to activate prekallikrein to KAL. As a result KAL has reduced efficacy in converting prorenin to renin and this step of the pathway leading to activation of renin affords a potential therapeutic target.

Chromogranin B: intra- and extra-cellular mechanisms to regulate catecholamine storage and release, in catecholaminergic cells and organisms.

Chromogranin B (CHGB) is the major matrix protein in human catecholamine storage vesicles. CHGB genetic variation alters catecholamine secretion and blood pressure. Here, effective Chgb protein under-expression was achieved by siRNA in PC12 cells, resulting in ~ 48% fewer secretory granules on electron microscopy, diminished capacity for catecholamine uptake (by ~ 79%), and a ~ 73% decline in stores available for nicotinic cholinergic-stimulated secretion. In vivo, loss of Chgb in knockout mice resulted in a ~ 35% decline in chromaffin granule abundance and ~ 44% decline in granule diameter, accompanied by unregulated catecholamine release into plasma. Over-expression of CHGB was achieved by transduction of a CHGB-expressing lentivirus, resulting in ~ 127% elevation in CHGB protein, with ~ 122% greater abundance of secretory granules, but only ~ 14% increased uptake of catecholamines, and no effect on nicotinic-triggered secretion. Human CHGB protein and its proteolytic fragments inhibited nicotinic-stimulated catecholamine release by ~ 72%. One conserved-region CHGB peptide inhibited nicotinic-triggered secretion by up to ~ 41%, with partial blockade of cationic signal transduction. We conclude that bi-directional quantitative derangements in CHGB abundance result in profound changes in vesicular storage and release of catecholamines. When processed and released extra-cellularly, CHGB proteolytic fragments exert a feedback effect to inhibit catecholamine secretion, especially during nicotinic cholinergic stimulation.

Genetic variation at the delta-sarcoglycan (SGCD) locus elevates heritable sympathetic nerve activity in human twin pairs.

The Syrian Cardiomyopathic Hamster (BIO-14.6/53.58 strains) model of cardiac failure, resulting from naturally occurring deletion at the SGCD (delta-sarcoglycan) locus, displays widespread disturbances in catecholamine metabolism. Rare Mendelian myopathy disorders of human SGCD occur, although common naturally occurring SGCD genetic variation has not been evaluated for effects on human norepinephrine (NE) secretion. This study investigated the effect of SGCD genetic variation on control of NE secretion in healthy twin pairs. Genetic associations profiled SNPs across the SGCD locus. Trait heritability (h(2)) and genetic covariance (pleiotropy; shared h(2)) were evaluated. Sympathochromaffin exocytosis in vivo was probed in plasma by both catecholamines and Chromogranin B (CHGB). Plasma NE is substantially heritable (p = 3.19E-16, at 65.2 ± 5.0% of trait variance), sharing significant (p < 0.05) genetic determination with circulating and urinary catecholamines, CHGB, eGFR, and several cardio-metabolic traits. Participants with higher pNE showed significant (p < 0.05) differences in several traits, including increased BP and hypertension risk factors. Peak SGCD variant rs1835919 predicted elevated systemic vascular compliance, without changes in specifically myocardial traits. We used a chimeric-regulated secretory pathway photoprotein (CHGA-EAP) to evaluate the effect of SGCD on the exocytotic pathway in transfected PC12 cells; in transfected cells, expression of SGCD augmented CHGA trafficking into the exocytotic regulated secretory pathway. Thus, our investigation determined human NE secretion to be a highly heritable trait, influenced by common genetic variation within the SGCD locus. Circulating NE aggregates with BP and hypertension risk factors. In addition, coordinate NE and CHGB elevation by rs1835919 implicates exocytosis as the mechanism of release.

Catecholamine biosynthesis and secretion: physiological and pharmacological effects of secretin.

Pituitary adenylyl cyclase activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) augment the biosynthesis of tyrosine hydroxylase (TH). We tested whether secretin belonging to the glucagon/PACAP/VIP superfamily would increase transcription of the tyrosine hydroxylase (Th) gene and modulate catecholamine secretion. Secretin activated transcription of the endogenous Th gene and its transfected promoter (EC(50) ∼4.6 nM) in pheochromocytoma (PC12) cells. This was abolished by pre-treatment with a secretin receptor (SCTR) antagonist and by inhibition of protein kinase A (PKA), mitogen-activated protein kinase, or CREB (cAMP response element-binding protein). In agreement, secretin increased PKA activity and induced phosphorylation of CREB and binding to Th CRE, suggesting secretin signaling to transcription via a PKA-CREB pathway. Secretin stimulated catecholamine secretion (EC(50) ∼3.5 µM) from PC12 cells, but this was inhibited by pre-treatment with VIP-preferring receptor (VPAC1)/PACAP-preferring receptor (PAC1) antagonists. Secretin-evoked secretion occurred without extracellular Ca(2+) and was abolished by intracellular Ca(2+) chelation. Secretin augmented phospholipase C (PLC) activity and increased inositol-1,4,5-triphosphate (IP(3)) levels in PC12 cells; PLC-ß inhibition blocked secretin-induced catecholamine secretion, indicating the participation of intracellular Ca(2+) from a phospholipase pathway in secretion. Like PACAP, secretin evoked long-lasting catecholamine secretion, even after only a transient exposure. Thus, transcription is triggered by nanomolar concentrations of the peptide through SCTR, with signaling along the cAMP-PKA and extracellular-signal-regulated kinase 1/2 pathways and through CREB. By contrast, secretion is triggered only by micromolar concentrations of peptide through PAC1/VPAC receptors and by utilizing a PLC/intracellular Ca(2+) pathway.

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.

Renal kallikrein excretion and epigenetics in human acute kidney injury: expression, mechanisms and consequences.

BACKGROUND: Renal kallikrein (KLK1) synthesis and urinary excretion are reportedly diminished during AKI (acute kidney injury) in animal models, and provision of kallikrein abrogates renal injury in this setting, but data in human AKI is limited. Therefore we first examined KLK1 renal excretion in human AKI, and then probed potential endocrine and epigenetic mechanisms for its alterations. METHODS: KLK1 enzymatic activity excretion was evaluated in urine from patients with established or incipient AKI, versus healthy/non-hospital as well as ICU controls. Endocrine control of KLK1 excretion was then probed by catecholamine and aldosterone measurements in established AKI versus healthy controls. To examine epigenetic control of KLK1 synthesis, we tested blood and urine DNA for changes in promoter CpG methylation of the KLK1 gene, as well as LINE-1 elements, by bisulfite sequencing. RESULTS: Patients with early/incipient AKI displayed a modest reduction of KLK1 excretion, but unexpectedly, established AKI displayed substantially elevated urine KLK1 excretion, ~11-fold higher than healthy controls, and ~3-fold greater than ICU controls. We then probed potential mechanisms of the change. Established AKI patients had lower SBP, higher heart rate, and higher epinephrine excretion than healthy controls, though aldosterone excretion was not different. Promoter KLK1 CpG methylation was higher in blood than urine DNA, while KLK1 methylation in blood DNA was significantly higher in established AKI than healthy controls, though KLK1 methylation in urine tended to be higher in AKI, directionally consistent with earlier/incipient but not later/established changes in KLK1 excretion in AKI. On multivariate ANOVA, AKI displayed coordinate changes in KLK1 excretion and promoter methylation, though directionally opposite to expectation. Control (LINE-1 repetitive element) methylation in blood and urine DNA was similar between AKI and controls. CONCLUSIONS: Unexpectedly, increased KLK1 excretion in AKI patients was found; this increase is likely to be due in part to increments in adrenergic tone during BP depression. Epigenetic changes at KLK1 may also play a role in early changes of KLK1 expression and thus AKI susceptibility or recovery.

Progression of chronic kidney disease: Adrenergic genetic influence on glomerular filtration rate decline in hypertensive nephrosclerosis.

BACKGROUND: African-Americans are likely to develop hypertension and hypertensive nephrosclerosis. This grave prognosis, coupled with familial aggregation of end-stage renal disease (ESRD) in Blacks, prompts a search for genetic risk factors for ESRD. Recent evidence implicates a crucial role for the sympathetic nervous system in progressive renal disease. METHODS: We used the African-American Study of Kidney Disease to probe whether beta2-adrenergic receptor (ADRB2) predicts glomerular filtration rate (GFR) decline rate. A total of 580 participants were included. Baseline GFR was 51.2 +/- 0.5 ml/min/1.73 m2. Subjects were randomized in a 2 x 3 block design: to intensively lowered (MAP < or = 92 mm Hg) versus 'usual' (MAP = 102-107 mm Hg) blood pressure goal groups, and also divided by three randomized antihypertensive drugs (ramipril, metoprolol, or amlodipine). We scored 4 SNPs at the ADRB2 locus. RESULTS: Haplotypes at ADRB2 predicted chronic GFR decline rate, GFR declined more slowly in individuals with haplotype-1 (-804G-->173T-->16Gly-->27GIn), and faster in those who carried haplotype-3 (-804G-->173T-->16Arg-->27Gln). ADRB2 genotype interacted with antihypertensive drug class to influence GFR slope (p = 0.001-0.037). We extended our findings to an independent case/control sample of Black hypertensive ESRD, in which we found that variant Gly16Arg that tagged the GFR slope-determining ADRB2 haplotype also conferred risk for the ESRD trait in Blacks. CONCLUSIONS: The GFR decline/progression rate in hypertensive renal disease is controlled in part by genetic variation within the adrenergic pathway.

Common charge-shift mutation Glu65Lys in K+ channel ß1-Subunit KCNMB1: pleiotropic consequences for glomerular filtration rate and progressive renal disease.

BACKGROUND: Glomerular filtration rate (GFR) is a heritable trait, and hyperfiltration (GFR increment in remnant nephrons) may accelerate renal functional decline in chronic kidney disease (CKD). Mesangial and vascular smooth myocytes control GFR by contraction, dependent on voltage-gated Ca(2+) influx, which is controlled by the regulatory ß1-subunit (KCNMB1) of large-conductance heteromeric K+ ('BK') channels. KCNMB1 gain-of-function variant Glu65Lys results in generalized vasorelaxation and thus protection against systemic hypertension. Here we asked whether the Glu65Lys variant influences GFR, in the basal state or during progressive renal decline. METHODS: We explored Glu65Lys effects on GFR in three populations spanning two ethnicities and two diseases (hypertension and nephrosclerosis). GFR was either estimated (eGFR from serum creatinine) or directly measured (iothalamate clearance). RESULTS: The 65Lys variant was relatively common, occurring on ∼5-10% of chromosomes in different biogeographic ancestry groups, and 65Lys carriers exhibited higher eGFR in two primary care populations: extreme BP values in Kaiser clinics (p = 0.029, accounting for ∼0.2% of trait variance), or treated hypertensives in VA clinics (p = 0.017, accounting for ∼0.9% of trait variance). In blacks with progressive renal disease (NIDDK AASK), 65Lys carriers displayed a steeper slope in GFR chronic decline (p = 0.030, accounting for ∼0.4% of trait variance), and Glu65Lys genotype also predicted time of onset of renal failure (log rank p = 0.019). CONCLUSIONS: Common KCNMB1 gain-of-function variant Glu65Lys influences GFR, and 65Lys carriers exhibit not only elevated baseline GFR, but also more rapid GFR decline (and consequent development of renal failure) in CKD. The results suggest that profiling patients at Glu65Lys can assist in gauging renal prognosis as well as selection of rational therapy in hypertension with progressive renal disease.

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.

Phenylethanolamine N-methyltransferase gene polymorphisms and adverse outcomes in acute kidney injury.

BACKGROUND/AIMS: The catecholaminergic pathway is important in the physical stress response; however, its role is not well understood in acute kidney injury (AKI). We studied single nucleotide polymorphisms (SNPs) of phenylethanolamine N-methyltransferase (PNMT), the terminal enzyme of the catecholaminergic pathway, and their association with adverse outcomes in AKI. METHODS: We performed a case-control study of 961 Caucasian subjects (194 with AKI and 767 controls). The PNMT promoter G-161A (rs876493) and coding A+1543G (rs5638) SNPs were genotyped and haplotypes generated. The outcomes of interest were the development of AKI, in-hospital mortality, dialysis requirement, oliguria, and hemodynamic shock. Urine catecholamines were measured in cases to explore genotype-phenotype correlations. RESULTS: The PNMT +1543 G allele was associated with AKI [odds ratio (OR) 2.19, 95% confidence interval (CI): 1.04-4.60]. For AKI cases, each PNMT -161 A allele was associated with lower mortality (OR 0.58, 95% CI: 0.35-0.99) and hemodynamic shock (OR 0.63, 95% CI: 0.40-1.00). The PNMT +1543 G allele was associated with oliguria (OR 3.35, 95% CI: 1.13-9.95). Urine adrenaline was associated with increased hemodynamic shock and mortality, but was lowest in PNMT -161 A/A carriers. CONCLUSION: In Caucasians, PNMT SNPs are associated with the development of AKI, disease severity, and in-hospital mortality. The adrenergic pathway provides another area of focus in the study of AKI.

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.

Author Correction: A new common functional coding variant at the DDC gene change renal enzyme activity and modify renal dopamine function.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Heritability and genome-wide linkage in US and australian twins identify novel genomic regions controlling chromogranin a: implications for secretion and blood pressure.

BACKGROUND: Chromogranin A (CHGA) triggers catecholamine secretory granule biogenesis, and its catestatin fragment inhibits catecholamine release. We approached catestatin heritability using twin pairs, coupled with genome-wide linkage, in a series of twin and sibling pairs from 2 continents. METHODS AND RESULTS: Hypertensive patients had elevated CHGA coupled with reduction in catestatin, suggesting diminished conversion of precursor to catestatin. Heritability for catestatin in twins was 44% to 60%. Six hundred fifteen nuclear families yielded 870 sib pairs for linkage, with significant logarithm of odds peaks on chromosomes 4p, 4q, and 17q. Because acidification of catecholamine secretory vesicles determines CHGA trafficking and processing to catestatin, we genotyped at positional candidate ATP6N1, bracketed by peak linkage markers on chromosome 17q, encoding a subunit of vesicular H(+)-translocating ATPase. The minor allele diminished CHGA secretion and processing to catestatin. The ATP6N1 variant also influenced blood pressure in 1178 individuals with the most extreme blood pressure values in the population. In chromaffin cells, inhibition of H(+)-ATPase diverted CHGA from regulated to constitutive secretory pathways. CONCLUSIONS: We established heritability of catestatin in twins from 2 continents. Linkage identified 3 regions contributing to catestatin, likely novel determinants of sympathochromaffin exocytosis. At 1 such positional candidate (ATP6N1), variation influenced CHGA secretion and processing to catestatin, confirming the mechanism of a novel trans-QTL for sympathochromaffin activity and blood pressure.

Adrenergic beta-1 receptor genetic variation predicts longitudinal rate of GFR decline in hypertensive nephrosclerosis.

BACKGROUND: End-stage renal disease (ESRD) due to hypertension is common and displays familial aggregation in African Americans, suggesting genetic risk factors, including adrenergic activity alterations which are noted in both hypertension and ESRD. METHODS: We analysed 554 hypertensive nephrosclerosis participants (without clinically significant proteinuria) from the longitudinal National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) African American Study of Kidney Disease and Hypertension (AASK) cohort to determine whether decline in glomerular filtration rate (GFR) over approximately 3.8 years was predicted by common genetic variation within the adrenergic beta-1 (ADRB1) receptor at non-synonymous positions Ser49Gly and Arg389Gly. RESULTS: The polymorphism at Ser49Gly (though not Arg389Gly, in only partial linkage disequilibrium at r(2) = 0.18) predicted the chronic rate of GFR decline, with minimal decline in Gly(49)/Gly(49) (minor allele) homozygotes compared to Ser(49) carriers; concordant results were observed for haplotypes and diploid haplotype pairs at the locus. An independent replication study in 1244 subjects from the San Diego Veterans Affairs Hypertension Cohort confirmed that Gly(49)/Gly(49) homozygotes displayed the least rapid decline of eGFR over approximately 3.6 years. CONCLUSION: We conclude that GFR decline rate in hypertensive renal disease is controlled in part by genetic variation within the adrenergic pathway, particularly at ADRB1. The results suggest novel strategies to approach the role of the adrenergic system in the risk and treatment of progressive renal disease.

Chromogranin A polymorphisms are associated with hypertensive renal disease.

Chromogranin A is released together with epinephrine and norepinephrine from catecholaminergic cells. Specific endopeptidases cleave chromogranin A into biologically active peptide fragments, including catestatin, which inhibits catecholamine release. Previous studies have suggested that a deficit in this sympathetic "braking" system might be an early event in the pathogenesis of human hypertension. Whether chromogranin A (CHGA) polymorphisms predict end-organ complications of hypertension, such as end-stage renal disease, is unknown. Among blacks, we studied common genetic variants spanning the CHGA locus in 2 independent case-control studies of hypertensive ESRD. Two haplotypes were significantly more frequent among subjects with hypertensive ESRD: 1) in the promoter (5') region, G-462A-->T-415C-->C-89A, haplotype ATC (adjusted odds ratio = 2.65; P = 0.037), and 2) at the 3'-end, C11825T (3'-UTR, C+87T)-->G12602C, haplotype TC (adjusted odds ratio = 2.73, P = 0.0196). Circulating levels of catestatin were lower among those with hypertensive ESRD than controls, an unexpected finding given that peptide levels are usually elevated in ESRD because of reduced renal elimination. We found that the 3'-UTR + 87T variant decreased reporter gene expression, providing a possible mechanistic explanation for diminished catestatin. In summary, common variants in chromogranin A associate with the risk of hypertensive ESRD in blacks.

A new common functional coding variant at the DDC gene change renal enzyme activity and modify renal dopamine function.

The intra-renal dopamine (DA) system is highly expressed in the proximal tubule and contributes to Na+ and blood pressure homeostasis, as well as to the development of nephropathy. In the kidney, the enzyme DOPA Decarboxylase (DDC) originating from the circulation. We used a twin/family study design, followed by polymorphism association analysis at DDC locus to elucidate heritable influences on renal DA production. Dense single nucleotide polymorphism (SNP) genotyping across the DDC locus on chromosome 7p12 was analyzed by re-sequencing guided by trait-associated genetic markers to discover the responsible genetic variation. We also characterized kinetics of the expressed DDC mutant enzyme. Systematic polymorphism screening across the 15-Exon DDC locus revealed a single coding variant in Exon-14 that was associated with DA excretion and multiple other renal traits indicating pleiotropy. When expressed and characterized in eukaryotic cells, the 462Gln variant displayed lower Vmax (maximal rate of product formation by an enzyme) (21.3 versus 44.9 nmol/min/mg) and lower Km (substrate concentration at which half-maximal product formation is achieved by an enzyme.)(36.2 versus 46.8 µM) than the wild-type (Arg462) allele. The highly heritable DA excretion trait is substantially influenced by a previously uncharacterized common coding variant (Arg462Gln) at the DDC gene that affects multiple renal tubular and glomerular traits, and predicts accelerated functional decline in chronic kidney disease.