Sickle Trait and Alpha Thalassemia Increase NOS-Dependent Vasodilation of Human Arteries Through Disruption of Endothelial Hemoglobin-eNOS Interactions
Abstract
BACKGROUND: Severe malaria is associated with impaired nitric oxide (NO) synthase (NOS)–dependent vasodilation, and reversal of this deficit improves survival in murine models. Malaria might have selected for genetic polymorphisms that increase endothelial NO signaling and now contribute to heterogeneity in vascular function among humans. One protein potentially selected for is alpha globin, which, in mouse models, interacts with endothelial NOS (eNOS) to negatively regulate NO signaling. We sought to evaluate the impact of alpha globin gene deletions on NO signaling and unexpectedly found human arteries use not only alpha but also beta globin to regulate eNOS. METHODS: The eNOS-hemoglobin complex was characterized by multiphoton imaging, gene expression analysis, and coimmunoprecipitation studies of human resistance arteries. Novel contacts between eNOS and hemoglobin were mapped using molecular modeling and simulation. Pharmacological or genetic disruption of the eNOS-hemoglobin complex was evaluated using pressure myography. The association between alpha globin gene deletion and blood pressure was assessed in a population study. RESULTS: Alpha and beta globin transcripts were detected in the endothelial layer of the artery wall. Imaging colocalized alpha and beta globin proteins with eNOS at myoendothelial junctions. Immunoprecipitation demonstrated that alpha globin and beta globin form a complex with eNOS and cytochrome b5 reductase. Modeling predicted negatively charged glutamic acids at positions 6 and 7 of beta globin to interact with positively charged arginines at positions 97 and 98 of eNOS. Arteries from donors with a glutamic acid–to–valine substitution at beta globin position 6 (sickle trait) exhibited increased NOS-dependent vasodilation. Alpha globin gene deletions were associated with decreased arterial alpha globin expression, increased NOS-dependent vasodilation, and lower blood pressure. Mimetic peptides that targeted the interactions between hemoglobin and eNOS recapitulated the effects of these genetic variants on human arterial vasoreactivity. CONCLUSIONS: Alpha and beta globin subunits of hemoglobin interact with eNOS to restrict NO signaling in human resistance arteries. Malaria-protective genetic variants that alter the expression of alpha globin or the structure of beta globin are associated with increased NOS-dependent vasodilation. Targeting the hemoglobin-eNOS interface could potentially improve NO signaling in diseases of endothelial dysfunction such as severe malaria or chronic cardiovascular conditions.
Article Details
Authors (27)
Steven D. Brooks
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
A. Parker Ruhl
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Xianke Zeng
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Phillip Cruz
Bioinformatics and Computational Biosciences Branch, Office of Cyber Infrastructure and Computational Biology (P.C., S.A.H.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Sergio A. Hassan
Bioinformatics and Computational Biosciences Branch, National Institute of Allergy and Infectious Diseases (NIAID)
Olena Kamenyeva
Md Abdul Hakim
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Lauryn A. Ridley
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Bianca M. Nagata
Juraj Kabat
Sundar Ganesan
Rachel L. Smith
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Mary Jackson
Jessica Nino de Rivera
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Alison J. McLure
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Jarrett M. Jackson
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Robert O. Emeh
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Naomi Tesfuzigta
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Kyeisha Laurence
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.
Stacy Joyce
Surgical Oncology Program, Center for Cancer Research, National Cancer Institute, Bethesda, MD (S.J., J.L.D.).
Christina Yek
International Center of Excellence in Research, National Institute of Allergy and Infectious Diseases, Phnom Penh, Cambodia (C.Y., S.C., J.M.).
Sophana Chea
International Center of Excellence in Research, National Institute of Allergy and Infectious Diseases, Phnom Penh, Cambodia (C.Y., S.C., J.M.).
Derron A. Alves
Brant E. Isakson
Jessica Manning
Jeremy L. Davis
Surgical Oncology Program, Center for Cancer Research, National Cancer Institute, Bethesda, MD (S.J., J.L.D.).
Hans C. Ackerman
Physiology Unit, Laboratory of Malaria and Vector Research (S.D.B., A.P.R., X.Z., M.A.H., L.A.R., R.L.S., M.J., J.N.d.R., A.J.M., J.M.J., R.O.E., N.T., K.L., H.C.A.), National Institute of Allergy and Infectious Diseases, Rockville, MD.