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Abbineni PS, Baid S, Weiss MJ. A moonlighting job for α-globin in blood vessels. Blood 2024; 144:834-844. [PMID: 38848504 DOI: 10.1182/blood.2023022192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 05/08/2024] [Accepted: 05/28/2024] [Indexed: 06/09/2024] Open
Abstract
ABSTRACT Red blood cells express high levels of hemoglobin A tetramer (α2β2) to facilitate oxygen transport. Hemoglobin subunits and related proteins are also expressed at lower levels in other tissues across the animal kingdom. Physiological functions for most nonerythroid globins likely derive from their ability to catalyze reduction-oxidation (redox) reactions via electron transfer through heme-associated iron. An interesting example is illustrated by the recent discovery that α-globin without β-globin is expressed in some arteriolar endothelial cells (ECs). α-globin binds EC nitric oxide (NO) synthase (eNOS) and degrades its enzymatic product NO, a potent vasodilator. Thus, depletion of α-globin in ECs or inhibition of its association with eNOS causes arteriolar relaxation and lowering of blood pressure in mice. Some of these findings have been replicated in isolated human blood vessels, and genetic studies are tractable in populations in which α-thalassemia alleles are prevalent. Two small studies identified associations between loss of α-globin genes in humans and NO-regulated vascular responses elicited by local hypoxia-induced blood flow or thermal stimulation. In a few larger population-based studies, no associations were detected between loss of α-globin genes and blood pressure, ischemic stroke, or pulmonary hypertension. In contrast, a significant positive association between α-globin gene copy number and kidney disease was detected in an African American cohort. Further studies are required to define comprehensively the expression of α-globin in different vascular beds and ascertain their overall impact on normal and pathological vascular physiology.
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Affiliation(s)
- Prabhodh S Abbineni
- Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL
| | - Srishti Baid
- Life Sciences Institute, University of Michigan, Ann Arbor, MI
| | - Mitchell J Weiss
- Department of Hematology, St Jude Children's Research Hospital, Memphis, TN
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Vadolas J, Nualkaew T, Voon HPJ, Vilcassim S, Grigoriadis G. Interplay between α-thalassemia and β-hemoglobinopathies: Translating genotype-phenotype relationships into therapies. Hemasphere 2024; 8:e78. [PMID: 38752170 PMCID: PMC11094674 DOI: 10.1002/hem3.78] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 03/22/2024] [Accepted: 04/11/2024] [Indexed: 05/18/2024] Open
Abstract
α-Thalassemia represents one of the most important genetic modulators of β-hemoglobinopathies. During this last decade, the ongoing interest in characterizing genotype-phenotype relationships has yielded incredible insights into α-globin gene regulation and its impact on β-hemoglobinopathies. In this review, we provide a holistic update on α-globin gene expression stemming from DNA to RNA to protein, as well as epigenetic mechanisms that can impact gene expression and potentially influence phenotypic outcomes. Here, we highlight defined α-globin targeted strategies and rationalize the use of distinct molecular targets based on the restoration of balanced α/β-like globin chain synthesis. Considering the therapies that either increase β-globin synthesis or reactivate γ-globin gene expression, the modulation of α-globin chains as a disease modifier for β-hemoglobinopathies still remains largely uncharted in clinical studies.
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Affiliation(s)
- Jim Vadolas
- Centre for Cancer ResearchHudson Institute of Medical ResearchClaytonVictoriaAustralia
- Department of Molecular and Translational SciencesMonash UniversityClaytonVictoriaAustralia
| | - Tiwaporn Nualkaew
- Centre for Cancer ResearchHudson Institute of Medical ResearchClaytonVictoriaAustralia
- Present address:
Department of Medical Technology, School of Allied Health SciencesWalailak UniversityNakhon Si ThammaratThailand
| | - Hsiao P. J. Voon
- Department of Biochemistry and Molecular Biology, Cancer Program, Biomedicine Discovery InstituteMonash UniversityClaytonVictoriaAustralia
| | - Shahla Vilcassim
- Centre for Cancer ResearchHudson Institute of Medical ResearchClaytonVictoriaAustralia
- School of Clinical Sciences at Monash HealthMonash UniversityClaytonAustralia
| | - George Grigoriadis
- Centre for Cancer ResearchHudson Institute of Medical ResearchClaytonVictoriaAustralia
- School of Clinical Sciences at Monash HealthMonash UniversityClaytonAustralia
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Ruhl AP, Jackson JM, Carhuas CJ, Niño de Rivera JG, Fay MP, Weinberg JB, Que LG, Ackerman HC. Association of alpha globin gene copy number with exhaled nitric oxide in a cross-sectional study of healthy Black adults. BMJ Open Respir Res 2023; 10:e001714. [PMID: 38123476 DOI: 10.1136/bmjresp-2023-001714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 11/14/2023] [Indexed: 12/23/2023] Open
Abstract
INTRODUCTION The genetic determinants of fractional exhalation of nitric oxide (FeNO), a marker of lung inflammation, are understudied in Black individuals. Alpha globin (HBA) restricts nitric oxide signalling in arterial endothelial cells via interactions with nitric oxide synthase; however, its role in regulating the release of NO from respiratory epithelium is less well understood. We hypothesised that an HBA gene deletion, common among Black individuals, would be associated with higher FeNO. METHODS Healthy Black adults were enrolled at four study sites in North Carolina from 2005 to 2008. FeNO was measured in triplicate using a nitric oxide analyzer. The -3.7 kb HBA gene deletion was genotyped using droplet digital PCR on genomic DNA. The association of FeNO with HBA copy number was evaluated using multivariable linear regression employing a linear effect of HBA copy number and adjusting for age, sex and serum immunoglobulin-E levels. Post-hoc analysis employing a recessive mode of inheritance was performed. RESULTS 895 individuals were in enrolled in the study and 720 consented for future genetic research; 643 had complete data and were included in this analysis. Median (25th, 75th) FeNO was 20 (13, 31) ppb. HBA genotypes were: 30 (4.7%) -a/-a, 197 (30.6%) -a/aa, 405 (63%) aa/aa and 8 (1.2%) aa/aaa. Subjects were 35% male with median age 20 (19, 22) years. Multivariable linear regression analysis revealed no association between FeNO and HBA copy number (β=-0.005 (95% CI -0.042 to 0.033), p=0.81). In the post-hoc sensitivity analysis, homozygosity for the HBA gene deletion was associated with higher FeNO (β=0.107 (95% CI 0.003 to 0.212); p=0.045). CONCLUSION We found no association between HBA copy number and FeNO using a prespecified additive genetic model. However, a post hoc recessive genetic model found FeNO to be higher among subjects homozygous for the HBA deletion.
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Affiliation(s)
- A Parker Ruhl
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
- Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Jarrett M Jackson
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Carlos J Carhuas
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Jessica G Niño de Rivera
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Michael P Fay
- Biostatistics Research Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - J Brice Weinberg
- Department of Medicine and Division of Hematology, Duke University School of Medicine and Durham VA Medical Centers, Durham, North Carolina, USA
| | - Loretta G Que
- Department of Medicine and Division of Pulmonary, Allergy, and Critical Care Medicine, Duke University School of Medicine and Durham VA Medical Centers, Durham, North Carolina, USA
| | - Hans C Ackerman
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
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Xie X, Gan J, Liu Z, Zhou Y, Yuan K, Chen Z, Chen S, Zhou R, Liu L, Huang X, Zhang Y, Liu Q, Zhang W, Huang J, Chen J. Prevalence and genetic analysis of triplicated α-globin gene in Ganzhou region using high-throughput sequencing. Front Genet 2023; 14:1267892. [PMID: 37928241 PMCID: PMC10620506 DOI: 10.3389/fgene.2023.1267892] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 09/26/2023] [Indexed: 11/07/2023] Open
Abstract
α-globin gene triplication carriers were not anemic in general, while some studies found that α-globin gene triplication coinherited with heterozygous β-thalassemia may cause adverse clinical symptoms, which yet lacks sufficient evidence in large populations. In this study, we investigated the prevalence and distribution of α-globin gene triplication as well as the phenotypic characteristics of α-globin gene triplication coinherited with heterozygous β-thalassemia in Ganzhou city, southern China. During 2021-2022, a total of 73,967 random individuals who received routine health examinations before marriage were genotyped for globin gene mutations by high-throughput sequencing. Among them, 1,443 were α-globin gene triplication carriers, with a carrier rate of 1.95%. The most prevalent mutation was αααanti3.7/αα (43.10%), followed by αααanti4.2/αα (38.12%). 42 individuals had coinherited α-globin gene triplication and heterozygous β-thalassemia. However, they did not differ from the individuals with heterozygous β-thalassemia and normal α-globin (αα/αα) in terms of mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) levels. In addition, heterogenous clinical phenotypes were found in two individuals with the same genotype. Our study established a database of Ganzhou α-globin gene triplication and provided practical advice for the clinical diagnosis of α-globin gene triplication.
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Affiliation(s)
- Xinxing Xie
- Ganzhou Maternal and Child Health Hospital, Ganzhou, Jiangxi, China
| | - Jinhui Gan
- Ganzhou Maternal and Child Health Hospital, Ganzhou, Jiangxi, China
| | - Zezhang Liu
- BGI Genomics, Shenzhen, China
- Clin Lab, BGI Genomics, Wuhan, China
| | - Yulian Zhou
- Dayu Maternal and Child Health Hospital, Ganzhou, Jiangxi, China
| | - Kun Yuan
- BGI Genomics, Shenzhen, China
- Clin Lab, BGI Genomics, Wuhan, China
| | - Zhigang Chen
- BGI Genomics, Shenzhen, China
- Clin Lab, BGI Genomics, Wuhan, China
| | | | - Rui Zhou
- BGI Genomics, Shenzhen, China
- Clin Lab, BGI Genomics, Wuhan, China
| | - Lipei Liu
- BGI Genomics, Shenzhen, China
- Clin Lab, BGI Genomics, Tianjin, China
| | | | - Yan Zhang
- BGI Genomics, Shenzhen, China
- Clin Lab, BGI Genomics, Wuhan, China
| | - Qian Liu
- BGI Genomics, Shenzhen, China
- Clin Lab, BGI Genomics, Wuhan, China
| | - Wenqian Zhang
- BGI Genomics, Shenzhen, China
- Clin Lab, BGI Genomics, Wuhan, China
| | - Jungao Huang
- Ganzhou Maternal and Child Health Hospital, Ganzhou, Jiangxi, China
| | - Junkun Chen
- Ganzhou Maternal and Child Health Hospital, Ganzhou, Jiangxi, China
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Ruhl AP, Jeffries N, Yang Y, Brooks SD, Naik RP, Pecker LH, Mott BT, Winkler CA, Armstrong ND, Zakai NA, Gutierrez OM, Judd SE, Howard VJ, Howard G, Irvin MR, Cushman M, Ackerman HC. Alpha globin gene copy number and incident ischemic stroke risk among Black Americans. FRONTIERS IN STROKE 2023; 2:1192465. [PMID: 37622047 PMCID: PMC10448705 DOI: 10.3389/fstro.2023.1192465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/26/2023]
Abstract
Introduction People with African ancestry have greater stroke risk and greater heritability of stroke risk than people of other ancestries. Given the importance of nitric oxide (NO) in stroke, and recent evidence that alpha globin restricts nitric oxide release from vascular endothelial cells, we hypothesized that alpha globin gene (HBA) deletion would be associated with reduced risk of incident ischemic stroke. Methods We evaluated 8,947 participants self-reporting African ancestry in the national, prospective Reasons for Geographic And Racial Differences in Stroke (REGARDS) cohort. Incident ischemic stroke was defined as non-hemorrhagic stroke with focal neurological deficit lasting ≥ 24 hours confirmed by the medical record or focal or non-focal neurological deficit with positive imaging confirmed with medical records. Genomic DNA was analyzed using droplet digital PCR to determine HBA copy number. Multivariable Cox proportional hazards regression was used to estimate the hazard ratio (HR) of HBA copy number on time to first ischemic stroke. Results Four-hundred seventy-nine (5.3%) participants had an incident ischemic stroke over a median (IQR) of 11.0 (5.7, 14.0) years' follow-up. HBA copy number ranged from 2 to 6: 368 (4%) -α/-α, 2,480 (28%) -α/αα, 6,014 (67%) αα/αα, 83 (1%) ααα/αα and 2 (<1%) ααα/ααα. The adjusted HR of ischemic stroke with HBA copy number was 1.04; 95%CI 0.89, 1.21; p = 0.66. Conclusions Although a reduction in HBA copy number is expected to increase endothelial nitric oxide signaling in the human vascular endothelium, HBA copy number was not associated with incident ischemic stroke in this large cohort of Black Americans.
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Affiliation(s)
- A. Parker Ruhl
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
- Pulmonary Branch, National Heart, Lung, and Blood Institute, Bethesda, Maryland
| | - Neal Jeffries
- Office of Biostatistics Research, National Heart, Lung, and Blood Institute, Bethesda, Maryland
| | - Yu Yang
- Division of Blood Diseases and Resources, National Heart, Lung, and Blood Institute, Rockville, Maryland
| | - Steven D. Brooks
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Rakhi P. Naik
- Division of Hematology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Lydia H. Pecker
- Division of Hematology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Bryan T. Mott
- Wake Forest University School of Medicine, Winston-Salem, North Carolina:
| | - Cheryl A. Winkler
- Basic Research Laboratory, National Cancer Institute, Frederick National Laboratory for Cancer Research, Frederick, Maryland
| | - Nicole D. Armstrong
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Neil A. Zakai
- Department of Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont
- Department of Pathology & Laboratory Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont
| | - Orlando M. Gutierrez
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Suzanne E. Judd
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Virginia J. Howard
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - George Howard
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Marguerite R. Irvin
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Mary Cushman
- Department of Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont
- Department of Pathology & Laboratory Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont
| | - Hans C. Ackerman
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
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Ruhl AP, Jeffries N, Yang Y, Brooks SD, Naik RP, Pecker LH, Mott BT, Winkler CA, Armstrong ND, Zakai NA, Gutierrez OM, Judd SE, Howard VJ, Howard G, Irvin MR, Cushman M, Ackerman HC. Alpha globin gene copy number and incident ischemic stroke risk among Black Americans. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.03.15.23286908. [PMID: 36993674 PMCID: PMC10055557 DOI: 10.1101/2023.03.15.23286908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Introduction People with African ancestry have greater stroke risk and greater heritability of stroke risk than people of other ancestries. Given the importance of nitric oxide (NO) in stroke, and recent evidence that alpha globin restricts nitric oxide release from vascular endothelial cells, we hypothesized that alpha globin gene ( HBA) deletion would be associated with reduced risk of incident ischemic stroke. Methods We evaluated 8,947 participants self-reporting African ancestry in the national, prospective Reasons for Geographic And Racial Differences in Stroke (REGARDS) cohort. Incident ischemic stroke was defined as non-hemorrhagic stroke with focal neurological deficit lasting ≥ 24 hours confirmed by the medical record or focal or non-focal neurological deficit with positive imaging confirmed with medical records. Genomic DNA was analyzed using droplet digital PCR to determine HBA copy number. Multivariable Cox proportional hazards regression was used to estimate the hazard ratio (HR) of HBA copy number on time to first ischemic stroke. Results Four-hundred seventy-nine (5.3%) participants had an incident ischemic stroke over a median (IQR) of 11.0 (5.7, 14.0) years' follow-up. HBA copy number ranged from 2 to 6: 368 (4%) -α/-α, 2,480 (28%) -α/αα, 6,014 (67%) αα/αα, 83 (1%) ααα/αα and 2 (<1%) ααα/ααα. The adjusted HR of ischemic stroke with HBA copy number was 1.04; 95%CI 0.89, 1.21; p = 0.66. Conclusions Although a reduction in HBA copy number is expected to increase endothelial nitric oxide signaling in the human vascular endothelium, HBA copy number was not associated with incident ischemic stroke in this large cohort of Black Americans.
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Affiliation(s)
- A. Parker Ruhl
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
- Pulmonary Branch, National Heart, Lung, and Blood Institute, Bethesda, Maryland
| | - Neal Jeffries
- Office of Biostatistics Research, National Heart, Lung, and Blood Institute, Bethesda, Maryland
| | - Yu Yang
- Division of Blood Diseases and Resources, National Heart, Lung, and Blood Institute, Rockville, Maryland
| | - Steven D. Brooks
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | - Rakhi P. Naik
- Division of Hematology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Lydia H. Pecker
- Division of Hematology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Bryan T. Mott
- Wake Forest University School of Medicine, Winston-Salem, North Carolina:
| | - Cheryl A. Winkler
- Basic Research Laboratory, National Cancer Institute, Frederick National Laboratory for Cancer Research, Frederick, Maryland
| | - Nicole D. Armstrong
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Neil A. Zakai
- Department of Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont
- Department of Pathology & Laboratory Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont
| | - Orlando M. Gutierrez
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Suzanne E. Judd
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Virginia J. Howard
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - George Howard
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Marguerite R. Irvin
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Mary Cushman
- Department of Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont
- Department of Pathology & Laboratory Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont
| | - Hans C. Ackerman
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
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Alpha globin gene copy number and hypertension risk among Black Americans. PLoS One 2022; 17:e0271031. [PMID: 35834496 PMCID: PMC9282593 DOI: 10.1371/journal.pone.0271031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 06/22/2022] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND Alpha globin is expressed in the endothelial cells of human resistance arteries where it binds to endothelial nitric oxide synthase and limits release of the vasodilator nitric oxide. Genomic deletion of the alpha globin gene (HBA) is common among Black Americans and could lead to increased endothelial nitric oxide signaling and reduced risk of hypertension. METHODS Community-dwelling US adults aged 45 years or older were enrolled and examined from 2003 to 2007, followed by telephone every 6 months, and reexamined from 2013 to 2016. At both visits, trained personnel performed standardized, in-home blood pressure measurements and pill bottle review. Prevalent hypertension was defined as systolic blood pressure ≥ 140mmHg or diastolic blood pressure ≥ 90mmHg or anti-hypertensive medication use. Droplet digital PCR was used to determine HBA copy number. The associations of HBA copy number with prevalent hypertension, resistant hypertension, and incident hypertension were estimated using multivariable regression. RESULTS Among 9,684 Black participants, 7,439 (77%) had hypertension at baseline and 1,044 of those had treatment-resistant hypertension. 1,000 participants were not hypertensive at baseline and participated in a follow up visit; 517 (52%) developed hypertension over median 9.2 years follow-up. Increased HBA copy number was not associated with prevalent hypertension (PR = 1.00; 95%CI 0.98,1.02), resistant hypertension (PR = 0.95; 95%CI 0.86,1.05), or incident hypertension (RR = 0.96; 95%CI 0.86,1.07). CONCLUSIONS There were no associations between increased HBA copy number and risk of hypertension. These findings suggest that variation in alpha globin gene copy number does not modify the risk of hypertension among Black American adults.
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