Publications by authors named "Timothy J McMahon"

39 Publications

Pannexin 1 channels control the hemodynamic response to hypoxia by regulating O-sensitive extracellular ATP in blood.

Am J Physiol Heart Circ Physiol 2021 03 15;320(3):H1055-H1065. Epub 2021 Jan 15.

Department of Medicine, Marsico Lung Institute/UNC Cystic Fibrosis Research Center, University of North Carolina, Chapel Hill, North Carolina.

Pannexin 1 (Panx1) channels export ATP and may contribute to increased concentration of the vasodilator ATP in plasma during hypoxia in vivo. We hypothesized that Panx1 channels and associated ATP export contribute to hypoxic vasodilation, a mechanism that facilitates the matching of oxygen delivery to metabolic demand of tissue. Male and female mice devoid of Panx1 () and wild-type controls (WT) were anesthetized, mechanically ventilated, and instrumented with a carotid artery catheter or femoral artery flow transducer for hemodynamic and plasma ATP monitoring during inhalation of 21% (normoxia) or 10% oxygen (hypoxia). ATP export from WT vs. erythrocytes (RBC) was determined ex vivo via tonometer experimentation across progressive deoxygenation. Mean arterial pressure (MAP) was similar in ( = 6) and WT ( = 6) mice in normoxia, but the decrease in MAP in hypoxia seen in WT was attenuated in mice (-16 ± 9% vs. -2 ± 8%; < 0.05). Hindlimb blood flow (HBF) was significantly lower in ( = 6) vs. WT ( = 6) basally, and increased in WT but not mice during hypoxia (8 ± 6% vs. -10 ± 13%; < 0.05). Estimation of hindlimb vascular conductance using data from the MAP and HBF experiments showed an average response of 28% for WT vs. -9% for mice. Mean venous plasma ATP during hypoxia was 57% lower in ( = 6) vs. WT mice ( = 6; < 0.05). Mean hypoxia-induced ATP export from RBCs from mice ( = 8) was 82% lower than that from WT ( = 8; < 0.05). Panx1 channels participate in hemodynamic responses consistent with hypoxic vasodilation by regulating hypoxia-sensitive extracellular ATP levels in blood. Export of vasodilator ATP from red blood cells requires pannexin 1. Blood plasma ATP elevations in response to hypoxia in mice require pannexin 1. Hemodynamic responses to hypoxia are accompanied by increased plasma ATP in mice in vivo and require pannexin 1.
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http://dx.doi.org/10.1152/ajpheart.00651.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7988759PMC
March 2021

HGT in the human and skin commensal : A bacterially derived flavohemoglobin is required for NO resistance and host interaction.

Proc Natl Acad Sci U S A 2020 07 23;117(27):15884-15894. Epub 2020 Jun 23.

Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710;

The skin of humans and animals is colonized by commensal and pathogenic fungi and bacteria that share this ecological niche and have established microbial interactions. are the most abundant fungal skin inhabitant of warm-blooded animals and have been implicated in skin diseases and systemic disorders, including Crohn's disease and pancreatic cancer. Flavohemoglobin is a key enzyme involved in microbial nitrosative stress resistance and nitric oxide degradation. Comparative genomics and phylogenetic analyses within the genus revealed that flavohemoglobin-encoding genes were acquired through independent horizontal gene transfer events from different donor bacteria that are part of the mammalian microbiome. Through targeted gene deletion and functional complementation in , we demonstrated that bacterially derived flavohemoglobins are cytoplasmic proteins required for nitric oxide detoxification and nitrosative stress resistance under aerobic conditions. RNA-sequencing analysis revealed that endogenous accumulation of nitric oxide resulted in up-regulation of genes involved in stress response and down-regulation of the MalaS7 allergen-encoding genes. Solution of the high-resolution X-ray crystal structure of flavohemoglobin revealed features conserved with both bacterial and fungal flavohemoglobins. In vivo pathogenesis is independent of flavohemoglobin. Lastly, we identified an additional 30 genus- and species-specific horizontal gene transfer candidates that might have contributed to the evolution of this genus as the most common inhabitants of animal skin.
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http://dx.doi.org/10.1073/pnas.2003473117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7354939PMC
July 2020

Red Blood Cell Deformability, Vasoactive Mediators, and Adhesion.

Front Physiol 2019 15;10:1417. Epub 2019 Nov 15.

Durham VA Medical Center, Duke University, Durham, NC, United States.

Healthy red blood cells (RBCs) deform readily in response to shear stress in the circulation, facilitating their efficient passage through capillaries. RBCs also export vasoactive mediators in response to deformation and other physiological and pathological stimuli. Deoxygenation of RBC hemoglobin leads to the export of vasodilator and antiadhesive S-nitrosothiols (SNOs) and adenosine triphosphate (ATP) in parallel with oxygen transport in the respiratory cycle. Together, these mediated responses to shear stress and oxygen offloading promote the efficient flow of blood cells and in turn optimize oxygen delivery. In diseases including sickle cell anemia and conditions including conventional blood banking, these adaptive functions may be compromised as a result, for example, of limited RBC deformability, impaired mediator formation, or dysfunctional mediator export. Ongoing work, including single cell approaches, is examining relevant mechanisms and remedies in health and disease.
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http://dx.doi.org/10.3389/fphys.2019.01417DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6873820PMC
November 2019

Nitric oxide loading reduces sickle red cell adhesion and vaso-occlusion in vivo.

Blood Adv 2019 09;3(17):2586-2597

Division of Hematology and Duke Comprehensive Sickle Cell Center, Department of Medicine, Duke University Medical Center, Durham, NC.

Sickle red blood cells (SSRBCs) are adherent to the endothelium, activate leukocyte adhesion, and are deficient in bioactive nitric oxide (NO) adducts such as -nitrosothiols (SNOs), with reduced ability to induce vasodilation in response to hypoxia. All these pathophysiologic characteristics promote vascular occlusion, the hallmark of sickle cell disease (SCD). Loading hypoxic SSRBCs in vitro with NO followed by reoxygenation significantly decreased epinephrine-activated SSRBC adhesion to the endothelium, the ability of activated SSRBCs to mediate leukocyte adhesion in vitro and vessel obstruction in vivo. Because transfusion is frequently used in SCD, we also determined the effects of banked (SNO-depleted) red blood cells (RBCs) on vaso-occlusion in vivo. Fresh or 14-day-old normal RBCs (AARBCs) reduced epinephrine-activated SSRBC adhesion to the vascular endothelium and prevented vaso-occlusion. In contrast, AARBCs stored for 30 days failed to decrease activated SSRBC adhesivity or vaso-occlusion, unless these RBCs were loaded with NO. Furthermore, NO loading of SSRBCs increased -nitrosohemoglobin and modulated epinephrine's effect by upregulating phosphorylation of membrane proteins, including pyruvate kinase, E3 ubiquitin ligase, and the cytoskeletal protein 4.1. Thus, abnormal SSRBC NO/SNO content both contributes to the vaso-occlusive pathophysiology of SCD, potentially by affecting at least protein phosphorylation, and is potentially amenable to correction by (S)NO repletion or by RBC transfusion.
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http://dx.doi.org/10.1182/bloodadvances.2019031633DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6737414PMC
September 2019

Red blood cell phenotype fidelity following glycerol cryopreservation optimized for research purposes.

PLoS One 2018 21;13(12):e0209201. Epub 2018 Dec 21.

Department of Pediatrics, Divisions of Critical Care Medicine, Washington University in Saint Louis, School of Medicine, Saint Louis, MO, United States of America.

Intact red blood cells (RBCs) are required for phenotypic analyses. In order to allow separation (time and location) between subject encounter and sample analysis, we developed a research-specific RBC cryopreservation protocol and assessed its impact on data fidelity for key biochemical and physiological assays. RBCs drawn from healthy volunteers were aliquotted for immediate analysis or following glycerol-based cryopreservation, thawing, and deglycerolization. RBC phenotype was assessed by (1) scanning electron microscopy (SEM) imaging and standard morphometric RBC indices, (2) osmotic fragility, (3) deformability, (4) endothelial adhesion, (5) oxygen (O2) affinity, (6) ability to regulate hypoxic vasodilation, (7) nitric oxide (NO) content, (8) metabolomic phenotyping (at steady state, tracing with [1,2,3-13C3]glucose ± oxidative challenge with superoxide thermal source; SOTS-1), as well as in vivo quantification (following human to mouse RBC xenotransfusion) of (9) blood oxygenation content mapping and flow dynamics (velocity and adhesion). Our revised glycerolization protocol (40% v/v final) resulted in >98.5% RBC recovery following freezing (-80°C) and thawing (37°C), with no difference compared to the standard reported method (40% w/v final). Full deglycerolization (>99.9% glycerol removal) of 40% v/v final samples resulted in total cumulative lysis of ~8%, compared to ~12-15% with the standard method. The post cryopreservation/deglycerolization RBC phenotype was indistinguishable from that for fresh RBCs with regard to physical RBC parameters (morphology, volume, and density), osmotic fragility, deformability, endothelial adhesivity, O2 affinity, vasoregulation, metabolomics, and flow dynamics. These results indicate that RBC cryopreservation/deglycerolization in 40% v/v glycerol final does not significantly impact RBC phenotype (compared to fresh cells).
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0209201PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6303082PMC
May 2019

Drebrin regulates angiotensin II-induced aortic remodelling.

Cardiovasc Res 2018 11;114(13):1806-1815

Department of Medicine, Duke University Medical Center, 2301 Erwin Road, Durham, NC, USA.

Aims: The actin-binding protein Drebrin is up-regulated in response to arterial injury and reduces smooth muscle cell (SMC) migration and proliferation through its interaction with the actin cytoskeleton. We, therefore, tested the hypothesis that SMC Drebrin inhibits angiotensin II-induced remodelling of the proximal aorta.

Methods And Results: Angiotensin II was administered via osmotic minipumps at 1000 ng/kg/min continuously for 28 days in SM22-Cre+/Dbnflox/flox (SMC-Dbn-/-) and control mice. Blood pressure responses to angiotensin II were assessed by telemetry. After angiotensin II infusion, we assessed remodelling in the proximal ascending aorta by echocardiography and planimetry of histological cross sections. Although the degree of hypertension was equivalent in SMC-Dbn-/- and control mice, SMC-Dbn-/- mice nonetheless exhibited 60% more proximal aortic medial thickening and two-fold more outward aortic remodelling than control mice in response to angiotensin II. Proximal aortas demonstrated greater cellular proliferation and matrix deposition in SMC-Dbn-/- mice than in control mice, as evidenced by a higher prevalence of proliferating cell nuclear antigen-positive nuclei and higher levels of collagen I. Compared with control mouse aortas, SMC-Dbn-/- aortas demonstrated greater angiotensin II-induced NADPH oxidase activation and inflammation, evidenced by higher levels of Ser-536-phosphorylated NFκB p65 subunits and higher levels of vascular cell adhesion molecule-1, matrix metalloproteinase-9, and adventitial macrophages.

Conclusions: We conclude that SMC Drebrin deficiency augments angiotensin II-induced inflammation and adverse aortic remodelling.
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http://dx.doi.org/10.1093/cvr/cvy151DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6198746PMC
November 2018

Proceedings of the Food and Drug Administration's public workshop on new red blood cell product regulatory science 2016.

Transfusion 2018 01 15;58(1):255-266. Epub 2017 Dec 15.

Division of Transfusion Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.

The US Food and Drug Administration (FDA) held a workshop on red blood cell (RBC) product regulatory science on October 6 and 7, 2016, at the Natcher Conference Center on the National Institutes of Health (NIH) Campus in Bethesda, Maryland. The workshop was supported by the National Heart, Lung, and Blood Institute, NIH; the Department of Defense; the Office of the Assistant Secretary for Health, Department of Health and Human Services; and the Center for Biologics Evaluation and Research, FDA. The workshop reviewed the status and scientific basis of the current regulatory framework and the available scientific tools to expand it to evaluate innovative and future RBC transfusion products. A full record of the proceedings is available on the FDA website (http://www.fda.gov/BiologicsBloodVaccines/NewsEvents/WorkshopsMeetingsConferences/ucm507890.htm). The contents of the summary are the authors' opinions and do not represent agency policy.
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http://dx.doi.org/10.1111/trf.14435DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6258195PMC
January 2018

Biomarkers in Pulmonary Vascular Disease: Gauging Response to Therapy.

Am J Cardiol 2017 Oct;120(8S):S89-S95

Baylor College of Medicine, Houston, Texas.

Biomarkers are increasingly being investigated in the treatment of pulmonary vascular disease. In particular, the signaling pathways targeted by therapies for pulmonary arterial hypertension provide biomarkers that potentially can be used to guide therapy and to assess clinical response as an alternative to invasive procedures such as right-sided cardiac catheterization. Moreover, the growing use of combination therapy for both the initial and subsequent treatment of pulmonary arterial hypertension highlights the need for biomarkers in this treatment approach. Currently approved therapies for pulmonary arterial hypertension target 3 major signaling pathways: the nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate pathway, the endothelin pathway, and the prostacyclin pathway. Although the main biomarker used in practice and evaluated in clinical trials is N-terminal pro-brain natriuretic peptide, other putative biomarkers include the endogenous nitric oxide (NO) synthase inhibitor asymmetric dimethylarginine, NO metabolites including S-nitrosothiols and nitrite, exhaled NO, endothelins, cyclic guanosine monophosphate, cyclic adenosine monophosphate, and atrial natriuretic peptide. This review describes accessible biomarkers, related to the actual molecules targeted by current therapies, for measuring and predicting response to the individual pulmonary arterial hypertension treatment classes as well as combination therapy.
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http://dx.doi.org/10.1016/j.amjcard.2017.06.014DOI Listing
October 2017

Antagonists of the system L neutral amino acid transporter (LAT) promote endothelial adhesivity of human red blood cells.

Thromb Haemost 2017 06 6;117(7):1402-1411. Epub 2017 Apr 6.

Tim J. McMahon, MD, PhD, Duke University Medical Center, DUMC 103003, Medical Sciences Research Building 1, 203 Research Dr., Durham, NC 27710, USA, E-mail:

The system L neutral amino acid transporter (LAT; LAT1, LAT2, LAT3, or LAT4) has multiple functions in human biology, including the cellular import of S-nitrosothiols (SNOs), biologically active derivatives of nitric oxide (NO). SNO formation by haemoglobin within red blood cells (RBC) has been studied, but the conduit whereby a SNO leaves the RBC remains unidentified. Here we hypothesised that SNO export by RBCs may also depend on LAT activity, and investigated the role of RBC LAT in modulating SNO-sensitive RBC-endothelial cell (EC) adhesion. We used multiple pharmacologic inhibitors of LAT in vitro and in vivo to test the role of LAT in SNO export from RBCs and in thereby modulating RBC-EC adhesion. Inhibition of human RBC LAT by type-1-specific or nonspecific LAT antagonists increased RBC-endothelial adhesivity in vitro, and LAT inhibitors tended to increase post-transfusion RBC sequestration in the lung and decreased oxygenation in vivo. A LAT1-specific inhibitor attenuated SNO export from RBCs, and we demonstrated LAT1 in RBC membranes and LAT1 mRNA in reticulocytes. The proadhesive effects of inhibiting LAT1 could be overcome by supplemental L-CSNO (S-nitroso-L-cysteine), but not D-CSNO or L-Cys, and suggest a basal anti-adhesive role for stereospecific intercellular SNO transport. This study reveals for the first time a novel role of LAT1 in the export of SNOs from RBCs to prevent their adhesion to ECs. The findings have implications for the mechanisms of intercellular SNO signalling, and for thrombosis, sickle cell disease, and post-storage RBC transfusion, when RBC adhesivity is increased.
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http://dx.doi.org/10.1160/TH16-05-0373DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5755361PMC
June 2017

S-Nitrosylated fetal hemoglobin in neonatal human blood.

Biochem Biophys Res Commun 2016 05 6;473(4):1084-1089. Epub 2016 Apr 6.

Department of Medicine, Duke University and Durham VA Medical Centers, Durham, NC 27710, USA. Electronic address:

Background: Nitric oxide (NO) and its derivatives play important roles in the cardiopulmonary transition upon birth and in other oxygen-sensitive developmental milestones. One mechanism for the coupling of oxygen sensing and signaling by NO species is via the formation of an S-nitrosothiol (SNO) moiety on hemoglobin (Hb, forming SNO-Hb) and its release from the red blood cell in hypoxia. Although SNO-Hb formed on adult-type Hb (HbA, forming SNO-HbA) has been documented in physiological and pathophysiological human states, the fetal variant, SNO-HbF, has thus far not been isolated or characterized in human blood.

Methods And Results: We developed a technique capable of separating Hbs A and F under conditions that preserve SNO. We then measured SNO-HbF in the blood of healthy and premature or otherwise ill neonates using the gold standard for SNO measurement, mercury-coupled photolysis-chemiluminescence. SNO-HbF levels were in the range of those previously reported for HbA in adults. We found that SNO-HbF was more abundant at earlier gestational age (<30 weeks), even when accounting for the absolute HbF level.

Conclusions: The ability to monitor SNO-HbF could provide new insights into fetal development and the perinatal transition, and has potential as a biomarker relevant to the management of neonatal diseases.
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http://dx.doi.org/10.1016/j.bbrc.2016.04.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853255PMC
May 2016

Contact Lens Use in Patients With Boston Keratoprosthesis Type 1: Fitting, Management, and Complications.

Eye Contact Lens 2015 Nov;41(6):334-40

Department of Ophthalmology and Visual Sciences, University of Illinois Eye and Ear Infirmary, University of Illinois Hospital and Health System, Chicago, IL.

The Boston type 1 keratoprosthesis (KPro) is the most commonly used artificial cornea worldwide. Long-term bandage contact lenses are the standard of care for patients with these devices. The goal of bandage contact lenses is to maintain hydration and to protect the corneal tissue that surrounds the anterior plate of the keratoprosthesis which is vulnerable to desiccation, epithelial breakdown, dellen formation, and corneal melt. Contact lenses can also improve comfort, correct refractive errors, and improve the cosmesis of patients with artificial corneas. However, the continuous use of contact lenses places these patients at risk for complications such as lens loss, lens deposits, chronic conjunctivitis, and infection. In addition, obtaining an adequate fit in a patient with a compromised ocular surface and history of multiple surgeries including glaucoma drainage devices can present a challenge. This review discusses the types of contact lenses used, special fitting considerations, and common complications in patients with previous KPro surgery.
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http://dx.doi.org/10.1097/ICL.0000000000000154DOI Listing
November 2015

Restoration of intracellular ATP production in banked red blood cells improves inducible ATP export and suppresses RBC-endothelial adhesion.

Am J Physiol Heart Circ Physiol 2014 Dec 10;307(12):H1737-44. Epub 2014 Oct 10.

Department of Medicine, Division of Pulmonary, Allergy, Critical Care Medicine, Duke University Medical Center, Durham, North Carolina; and Durham Veterans Affairs Medical Center, Durham, North Carolina

Transfusion of banked red blood cells (RBCs) has been associated with poor cardiovascular outcomes. Storage-induced alterations in RBC glycolytic flux, attenuated ATP export, and microvascular adhesion of transfused RBCs in vivo could contribute, but the underlying mechanisms have not been tested. We tested the novel hypothesis that improving deoxygenation-induced metabolic flux and the associated intracellular ATP generation in stored RBCs (sRBCs) results in an increased extracellular ATP export and suppresses microvascular adhesion of RBCs to endothelium in vivo following transfusion. We show deficient intracellular ATP production and ATP export by human sRBCs during deoxygenation (impairments ~42% and 49%, respectively). sRBC pretreatment with a solution containing glycolytic intermediate/purine/phosphate precursors (i.e., "PIPA") restored deoxygenation-induced intracellular ATP production and promoted extracellular ATP export (improvement ~120% and 50%, respectively). In a nude mouse model of transfusion, adhesion of human RBCs to the microvasculature in vivo was examined. Only 2% of fresh RBCs (fRBCs) transfused adhered to the vascular wall, compared with 16% of sRBCs transfused. PIPA pretreatment of sRBCs significantly reduced adhesion to just 5%. In hypoxia, adhesion of sRBCs transfused was significantly augmented (up to 21%), but not following transfusion of fRBCs or PIPA-treated sRBCs (3.5% or 6%). Enhancing the capacity for deoxygenation-induced glycolytic flux within sRBCs increases their ability to generate intracellular ATP, improves the inducible export of extracellular anti-adhesive ATP, and consequently suppresses adhesion of stored, transfused RBCs to the vascular wall in vivo.
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http://dx.doi.org/10.1152/ajpheart.00542.2014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4269703PMC
December 2014

Randomized study of washing 40- to 42-day-stored red blood cells.

Transfusion 2014 Oct 16;54(10):2544-52. Epub 2014 Apr 16.

Duke Clinical Research Institute, Duke University, Durham, North Carolina.

Background: Pretransfusion washing of red blood cells (RBCs) stored for a longer duration may have theoretical advantages but few data exist to support this practice. In many hospital settings, use of a point-of-care cell washer could conceivably be used to quickly wash allogeneic RBCs before transfusion. The purpose of this preliminary study was to compare a point-of-care device with a common blood bank device for washing longer-stored RBCs.

Study Design And Methods: Forty RBC units stored for 40 to 42 days were randomized to washing with the COBE 2991 device (Terumo BCT; FDA-cleared for washing stored RBCs) or the Cell Saver Elite (Haemonetics; FDA-cleared point-of-care device for processing and washing fresh autologous shed whole blood). Supernatant and unit RBCs from unwashed (baseline) and washed blood were assayed for potassium, lactate, intracellular ATP, percentage of RBC recovery, cell-free hemoglobin, RBC microparticles, and RBCs were examined for susceptibility to hemolysis by physical stress.

Results: Both devices recovered a high percentage of RBCs and efficiently removed extracelluar potassium. Washing with the Elite resulted in significant increases in cell-free Hb, percent hemolysis, and RBC microparticle production, whereas washing with the COBE 2991 did not (fold Δ = 2.1 vs. 1.0, 4.6 vs. 1.2, 2.0 vs. 1.1, respectively; p < 0.05). Hemolysis induced by physical stress was not altered by washing.

Conclusion: Although point-of-care washing of longer-stored RBCs is appealing, these preliminary data suggest that transfusion of washed, longer-stored units could result in potentially greater exposure to plasma free Hb. More data are needed before this practice can be routinely recommended.
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http://dx.doi.org/10.1111/trf.12660DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4194130PMC
October 2014

Proteomic analysis of the NOS2 interactome in human airway epithelial cells.

Nitric Oxide 2013 Nov 21;34:37-46. Epub 2013 Feb 21.

Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Centers, Durham, NC 27710, United States. Electronic address:

The cytokine-inducible isoform of nitric oxide synthase (NOS2) is constitutively expressed in human respiratory epithelia and is upregulated in inflammatory lung disease. Here, we sought to better define the protein interactions that may be important for NOS2 activity and stability, as well as to identify potential targets of NOS2-derived NO, in the respiratory epithelium. We overexpressed Flag-tagged, catalytically-inactive NOS2 in A549 cells and used mass spectrometry to qualitatively identify NOS2 co-immunoprecipitating proteins. Stable isotope labeling of amino acids in cell culture (SILAC) was used to quantify the coordinate effects of cytokine stimulation on NOS2-protein interactions. Multi-protein networks dominated the NOS2 interactome, and cytokine-inducible interactions with allosteric activators and with the ubiquitin-proteasome system were correlated with cytokine-dependent increases in NO metabolites and in NOS2 ubiquitination. The ubiquitin ligase scaffolding protein, FBXO45, was identified as a novel, direct NOS2 interactor. Similar to the SPRY domain-containing SOCS box (SPSB) proteins, FBXO45 requires Asn27 in the (23)DINNN(27) motif of NOS2 for its interaction. However, FBXO45 is unique from the SPSBs in that it recruits a distinct E3 ligase complex containing MYCBP2 and SKP1. Collectively, these findings demonstrate the general utility of interaction proteomics for defining new aspects of NOS2 physiology.
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http://dx.doi.org/10.1016/j.niox.2013.02.079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3769490PMC
November 2013

Impact of transfusion of autologous 7- versus 42-day-old AS-3 red blood cells on tissue oxygenation and the microcirculation in healthy volunteers.

Transfusion 2012 Nov 27;52(11):2459-64. Epub 2012 Mar 27.

Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina 27710, USA.

Background: Stored red blood cells (RBCs) accumulate biochemical and biophysical changes. Maximum storage duration is based on acceptable in vitro characteristics and 24-hour survival, but not RBC function. Relatively little is known about the impact of RBC storage duration on oxygenation and the microcirculation.

Study Design And Methods: Eight healthy subjects donated a double RBC apheresis, which were prestorage leukoreduced and processed in AS-3. Subjects were transfused 1 unit of RBCs at 7 and 42 days after blood collection. Measurements of percentage of tissue oxygenation in the thenar eminence muscle (StO2) and brain (SctO2) were recorded with Food and Drug Administration-cleared noninvasive devices. Sublingual microvascular blood flow (microcirculatory flow index [MFI]) was quantified before and after RBC transfusion using a video microscope. Raw electronic data for all measurements were analyzed by a blinded observer at a core laboratory.

Results: The only pre- versus posttransfusion change observed in measurements of SctO2, StO2, or MFI was a very small increase in SctO2, from 70.4 to 71.8 (means, p=0.032) at 7 days. There was no significant difference in the amount of pre-post change at 7 days versus 42 days for any of the measures.

Conclusion: Transfusion of 1 unit of 42-day-stored RBCs to healthy subjects has no overt detrimental effect on tissue oxygenation or the microcirculation assessed by clinically available monitors.
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http://dx.doi.org/10.1111/j.1537-2995.2012.03615.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3387324PMC
November 2012

Transpulmonary flux of S-nitrosothiols and pulmonary vasodilation during nitric oxide inhalation: role of transport.

Am J Respir Cell Mol Biol 2012 Jul 9;47(1):37-43. Epub 2012 Feb 9.

Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, Duke University Medical Center, Durham, North Carolina, USA.

Inhaled nitric oxide (iNO) is used to treat pulmonary hypertension and is being investigated for prevention of bronchopulmonary dysplasia in neonates. Extrapulmonary effects of iNO are widely recognized, but the underlying chemistry and pharmacology are poorly understood. Growing evidence suggests that, in addition to acting via diffusion, NO can be converted into nitrosants capable of reacting with endogenous L-cysteine (L-Cys) in the alveolar lining fluid, forming S-nitrosothiol (SNO)-L-cysteine (CSNO). CSNO can then enter cells via the type L amino acid transporter (LAT). To determine the influence of LAT and supplemental L-Cys on the functional activity of iNO and transpulmonary movement of SNOs or other related species, we exposed C57Bl6 mice to nebulized L-Cys or D-cysteine (D-Cys) and/or LAT competitors. Isolated lungs were then perfused with physiologic buffer while effluent was collected to assay perfusate SNOs. Nebulized L-Cys, but not D-Cys, augmented the iNO-induced increase in circulating SNOs in the effluent without altering iNO-induced pulmonary vasodilation. Addition to the perfusate of either L-leucine (L-Leu) or 2-amino-2-norborane carboxylic acid, two distinct LAT competitors, inhibited appearance in the perfusate of SNOs in L-Cys-exposed lungs; a higher concentration of L-Leu significantly inhibited the iNO-induced pulmonary vasodilation as well as SNO accumulation. We conclude that iNO-induced pulmonary vasodilation and the transpulmonary movement of iNO-derived SNOs are mediated in part by formation of extracellular CSNO, uptake by alveolar epithelial LAT, and/or export by LAT from the pulmonary endothelium into the circulation. Therapies that exploit and optimize LAT-dependent SNO transport might improve the efficacy of and clinical outcomes with NO-based therapy by improving systemic SNO delivery.
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http://dx.doi.org/10.1165/rcmb.2011-0439OCDOI Listing
July 2012

Inhaled nitric oxide therapy increases blood nitrite, nitrate, and s-nitrosohemoglobin concentrations in infants with pulmonary hypertension.

J Pediatr 2012 Feb 9;160(2):245-51. Epub 2011 Sep 9.

Department of Pediatrics, Division of Neonatology, School of Medicine, Loma Linda University, Loma Linda, CA, USA.

Objective: To measure the circulating concentrations of nitric oxide (NO) adducts with NO bioactivity after inhaled NO (iNO) therapy in infants with pulmonary hypertension.

Study Design: In this single center study, 5 sequential blood samples were collected from infants with pulmonary hypertension before, during, and after therapy with iNO (n = 17). Samples were collected from a control group of hospitalized infants without pulmonary hypertension (n = 16) and from healthy adults for comparison (n = 12).

Results: After beginning iNO (20 ppm) whole blood nitrite levels increased approximately two-fold within 2 hours (P<.01). Whole blood nitrate levels increased to 4-fold higher than baseline during treatment with 20 ppm iNO (P<.01). S-nitrosohemoglobin increased measurably after beginning iNO (P<.01), whereas iron nitrosyl hemoglobin and total hemoglobin-bound NO-species compounds did not change.

Conclusion: Treatment of pulmonary hypertensive infants with iNO results in increases in levels of nitrite, nitrate, and S-nitrosohemoglobin in circulating blood. We speculate that these compounds may be carriers of NO bioactivity throughout the body and account for peripheral effects of iNO in the brain, heart, and other organs.
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http://dx.doi.org/10.1016/j.jpeds.2011.07.040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3237823PMC
February 2012

Impaired adenosine-5'-triphosphate release from red blood cells promotes their adhesion to endothelial cells: a mechanism of hypoxemia after transfusion.

Crit Care Med 2011 Nov;39(11):2478-86

Department of Medicine, Durham Veterans Administration and Duke University Medical Centers, Durham, NC, USA.

Objective: Transfusion of red blood cells has been linked to disappointing clinical outcomes in the critically ill, but specific mechanisms of organ dysfunction after transfusion remain poorly understood. We tested the hypothesis that red blood cell storage impairs the ability of red blood cells to release adenosine-5'-triphosphate and that impaired adenosine-5'-triphosphate release was injurious in vivo, in part through increased red blood cell adhesion.

Design: Prospective, controlled, mechanistic study.

Setting: University research laboratory.

Subjects: Human and mouse blood donors; nude mouse transfusion recipients.

Interventions: Manipulation of adenosine-5'-triphosphate release, supplemental adenosine-5'-triphosphate, and antibodies to red blood cell and endothelial adhesion receptors were used in vitro and in vivo to probe the roles of released adenosine-5'-triphosphate and adhesion in responses to (transfused) red blood cells.

Measurements And Main Results: The ability of stored red blood cells to release adenosine-5'-triphosphate declined markedly within 14 days after collection despite relatively stable levels of adenosine-5'-triphosphate within the red blood cells. Inhibiting adenosine-5'-triphosphate release promoted the adhesion of stored red blood cells to endothelial cells in vitro and red blood cell sequestration in the lungs of transfused mice in vivo. Unlike transfusion of fresh human red blood cells, stored red blood cell transfusion in mice decreased blood oxygenation and increased extravasation of red blood cells into the lung's alveolar air spaces. Similar findings were seen with transfusion of fresh red blood cells treated with the adenosine-5'-triphosphate release inhibitors glibenclamide and carbenoxolone. These findings were prevented by either coinfusion of an adenosine-5'-triphosphate analog or pretransfusion incubation of the red blood cells with an antibody against the erythrocyte adhesion receptor Landsteiner-Wiener (intercellular adhesion molecule-4).

Conclusions: The normal flow of red blood cells in pulmonary microvessels depends in part on the release of antiadhesive adenosine-5'-triphosphate from red blood cells, and storage-induced deficiency in adenosine-5'-triphosphate release from transfused red blood cells may promote or exacerbate microvascular pathophysiology in the lung, in part through increased red blood cell adhesion.
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http://dx.doi.org/10.1097/CCM.0b013e318225754fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3196852PMC
November 2011

Transport rather than diffusion-dependent route for nitric oxide gas activity in alveolar epithelium.

Free Radic Biol Med 2010 Jul 24;49(2):294-300. Epub 2010 Apr 24.

Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA.

The pathway by which inhaled NO gas enters pulmonary alveolar epithelial cells has not been directly tested. Although the expected mechanism is diffusion, another route is the formation of S-nitroso-L-cysteine, which then enters the cell through the L-type amino acid transporter (LAT). To determine if NO gas also enters alveolar epithelium this way, we exposed alveolar epithelial-rat type I, type II, L2, R3/1, and human A549-cells to NO gas at the air liquid interface in the presence of L- and D-cysteine+/-LAT competitors. NO gas exposure concentration dependently increased intracellular NO and S-nitrosothiol levels in the presence of L- but not D-cysteine, which was inhibited by LAT competitors, and was inversely proportional to diffusion distance. The effect of L-cysteine on NO uptake was also concentration dependent. Without preincubation with L-cysteine, NO uptake was significantly reduced. We found similar effects using ethyl nitrite gas in place of NO. Exposure to either gas induced activation of soluble guanylyl cylase in a parallel manner, consistent with LAT dependence. We conclude that NO gas uptake by alveolar epithelium achieves NO-based signaling predominantly by forming extracellular S-nitroso-L-cysteine that is taken up through LAT, rather than by diffusion. Augmenting extracellular S-nitroso-L-cysteine formation may augment pharmacological actions of inhaled NO gas.
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http://dx.doi.org/10.1016/j.freeradbiomed.2010.04.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2916064PMC
July 2010

Nitric oxide mediates relative airway hyporesponsiveness to lipopolysaccharide in surfactant protein A-deficient mice.

Am J Respir Cell Mol Biol 2011 Feb 26;44(2):175-84. Epub 2010 Mar 26.

Duke University Medical Center, Durham, NC 27710, USA.

Surfactant protein A (SP-A) mediates innate immune cell responses to LPS, a cell wall component of gram-negative bacteria that is found ubiquitously in the environment and is associated with adverse health effects. Inhaled LPS induces lung inflammation and increases airway responsiveness (AR). However, the role of SP-A in mediating LPS-induced AR is not well-defined. Nitric oxide (NO) is described as a potent bronchodilator, and previous studies showed that SP-A modulates the LPS-induced production of NO. Hence, we tested the hypothesis that increased AR, observed in response to aerosolized LPS exposure, would be significantly reduced in an SP-A-deficient condition. Wild-type (WT) and SP-A null (SP-A(-/-)) mice were challenged with aerosolized LPS. Results indicate that despite similar inflammatory indices, LPS-treated SP-A(-/-) mice had attenuated AR after methacholine challenge, compared with WT mice. The attenuated AR could not be attributed to inherent differences in SP-D concentrations or airway smooth muscle contractile and relaxation properties, because these measures were similar between WT and SP-A(-/-) mice. LPS-treated SP-A(-/-) mice, however, had elevated nitrite concentrations, inducible nitric oxide synthase (iNOS) expression, and NOS activity in their lungs. Moreover, the administration of the iNOS-specific inhibitor 1400W completely abrogated the attenuated AR. Thus, when exposed to aerosolized LPS, SP-A(-/-) mice demonstrate a relative airway hyporesponsiveness that appears to be mediated at least partly via an iNOS-dependent mechanism. These findings may have clinical significance, because recent studies reported associations between surfactant protein polymorphisms and a variety of lung diseases.
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http://dx.doi.org/10.1165/rcmb.2009-0284OCDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049231PMC
February 2011

Pulmonary alveolar epithelial uptake of S-nitrosothiols is regulated by L-type amino acid transporter.

Am J Physiol Lung Cell Mol Physiol 2008 Jul 25;295(1):L38-43. Epub 2008 Apr 25.

School of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.

Nitric oxide (NO) effects are often mediated via S-nitrosothiol (SNO) formation; SNO uptake has recently been shown to be mediated in some cell types via system L-type amino acid transporters (LAT-1, 2). Inhaled NO therapy may exert some biological effects via SNO formation. We therefore sought to determine if pulmonary epithelial SNO uptake depended on LAT or peptide transporter 2 (PEPT2). Both LAT-1 and PEPT2 proteins were detected by immunoblot and immunocytochemistry in L2 cells and rat lung. We tested SNO uptake through the transporters by exposing rat alveolar epithelial cells (L2 and type II) to RSNOs: S-nitrosoglutathione, S-nitrosocysteinylglycine (SNO-Cys-Gly), S-nitrosocysteine (CSNO), and to NO donor diethylamine NONOate (DEA-NONOate). SNO was detected in cell lysates by ozone chemiluminescence. NO uptake was detected by fluorescence in alveolar epithelial cells loaded with 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF-FM) diacetate cultured in submersion and exposed to RSNOs and DEA NONOate. Addition of L-Cys but not D-Cys to RSNOs or DEA NONOate increased SNO and DAF-FM signal that was inhibited by coincubation with LAT competitors. Incubation of cells with PEPT2 substrate SNO-Cys-Gly showed no increase in SNO or DAF-FM signal unless incubated with L-Cys. This was unaffected by PEPT2 inhibition. We conclude that RSNOs (thionitrites, S-nitrosothiols) and NO enter alveolar epithelial cells predominantly by S-nitrosation of L-Cys, which is then imported through LAT.
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http://dx.doi.org/10.1152/ajplung.00280.2007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2494774PMC
July 2008

Evolution of adverse changes in stored RBCs.

Proc Natl Acad Sci U S A 2007 Oct 11;104(43):17063-8. Epub 2007 Oct 11.

Department of Anesthesiology, Duke Clinical Research Institute, Duke University Medical Center, Durham, NC 27710, USA.

Recent studies have underscored questions about the balance of risk and benefit of RBC transfusion. A better understanding of the nature and timing of molecular and functional changes in stored RBCs may provide strategies to improve the balance of benefit and risk of RBC transfusion. We analyzed changes occurring during RBC storage focusing on RBC deformability, RBC-dependent vasoregulatory function, and S-nitrosohemoglobin (SNO-Hb), through which hemoglobin (Hb) O(2) desaturation is coupled to regional increases in blood flow in vivo (hypoxic vasodilation). Five hundred ml of blood from each of 15 healthy volunteers was processed into leukofiltered, additive solution 3-exposed RBCs and stored at 1-6 degrees C according to AABB standards. Blood was subjected to 26 assays at 0, 3, 8, 24 and 96 h, and at 1, 2, 3, 4, and 6 weeks. RBC SNO-Hb decreased rapidly (1.2 x 10(-4) at 3 h vs. 6.5 x 10(-4) (fresh) mol S-nitrosothiol (SNO)/mol Hb tetramer (P = 0.032, mercuric-displaced photolysis-chemiluminescence assay), and remained low over the 42-day period. The decline was corroborated by using the carbon monoxide-saturated copper-cysteine assay [3.0 x 10(-5) at 3 h vs. 9.0 x 10(-5) (fresh) mol SNO/mol Hb]. In parallel, vasodilation by stored RBCs was significantly depressed. RBC deformability assayed at a physiological shear stress decreased gradually over the 42-day period (P < 0.001). Time courses vary for several storage-induced defects that might account for recent observations linking blood transfusion with adverse outcomes. Of clinical concern is that SNO levels, and their physiological correlate, RBC-dependent vasodilation, become depressed soon after collection, suggesting that even "fresh" blood may have developed adverse biological characteristics.
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http://dx.doi.org/10.1073/pnas.0708160104DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2040393PMC
October 2007

Transport and peripheral bioactivities of nitrogen oxides carried by red blood cell hemoglobin: role in oxygen delivery.

Physiology (Bethesda) 2007 Apr;22:97-112

Université Catholique de Louvain (UCL), Unit of Pharmacology & Therapeutics, Brussels, Belgium.

The biology of NO (nitric oxide) is poorly explained by the activity of the free radical NO ((.)NO) itself. Although (.)NO acts in an autocrine and paracrine manner, it is also in chemical equilibrium with other NO species that constitute stable stores of NO bioactivity. Among these species, S-nitrosylated hemoglobin (S-nitrosohemoglobin; SNO-Hb) is an evolved transducer of NO bioactivity that acts in a responsive and exquisitely regulated manner to control cardiopulmonary and vascular homeostasis. In SNO-Hb, O(2) sensing is dynamically coupled to formation and release of vasodilating SNOs, endowing the red blood cell (RBC) with the capacity to regulate its own principal function, O(2) delivery, via regulation of blood flow. Analogous, physiological actions of RBC SNO-Hb also contribute to central nervous responses to blood hypoxia, the uptake of O(2) from the lung to blood, and baroreceptor-mediated control of the systemic flow of blood. Dysregulation of the formation, export, or actions of RBC-derived SNOs has been implicated in human diseases including sepsis, sickle cell anemia, pulmonary arterial hypertension, and diabetes mellitus. Delivery of SNOs by the RBC can be harnessed for therapeutic gain, and early results support the logic of this approach in the treatment of diseases as varied as cancer and neonatal pulmonary hypertension.
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http://dx.doi.org/10.1152/physiol.00042.2006DOI Listing
April 2007

Excitation-contraction coupling in airway smooth muscle.

J Biol Chem 2006 Oct 6;281(40):30143-51. Epub 2006 Aug 6.

Division of Pulmonary, Allergy and Critical Care Medicine, Duke University, Medical Center, Durham, North Carolina 27710, USA.

Excitation-contraction (EC) coupling in striated muscles is mediated by the cardiac or skeletal muscle isoform of voltage-dependent L-type Ca(2+) channel (Ca(v)1.2 and Ca(v)1.1, respectively) that senses a depolarization of the cell membrane, and in response, activates its corresponding isoform of intracellular Ca(2+) release channel/ryanodine receptor (RyR) to release stored Ca(2+), thereby initiating muscle contraction. Specifically, in cardiac muscle following cell membrane depolarization, Ca(v)1.2 activates cardiac RyR (RyR2) through an influx of extracellular Ca(2+). In contrast, in skeletal muscle, Ca(v)1.1 activates skeletal muscle RyR (RyR1) through a direct physical coupling that negates the need for extracellular Ca(2+). Since airway smooth muscle (ASM) expresses Ca(v)1.2 and all three RyR isoforms, we examined whether a cardiac muscle type of EC coupling also mediates contraction in this tissue. We found that the sustained contractions of rat ASM preparations induced by depolarization with KCl were indeed partially reversed ( approximately 40%) by 200 mum ryanodine, thus indicating a functional coupling of L-type channels and RyRs in ASM. However, KCl still caused transient ASM contractions and stored Ca(2+) release in cultured ASM cells without extracellular Ca(2+). Further analyses of rat ASM indicated that this tissue expresses as many as four L-type channel isoforms, including Ca(v)1.1. Moreover, Ca(v)1.1 and RyR1 in rat ASM cells have a similar distribution near the cell membrane in rat ASM cells and thus may be directly coupled as in skeletal muscle. Collectively, our data implicate that EC-coupling mechanisms in striated muscles may also broadly transduce diverse smooth muscle functions.
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http://dx.doi.org/10.1074/jbc.M606541200DOI Listing
October 2006

Extrapulmonary effects of inhaled nitric oxide: role of reversible S-nitrosylation of erythrocytic hemoglobin.

Proc Am Thorac Soc 2006 Apr;3(2):153-60

Durham Veterans Affairs and Duke University Medical Centers, Durham, North Carolina 27710, USA.

Early applications of inhaled nitric oxide (iNO), typically in the treatment of diseases marked by acute pulmonary hypertension, were met by great enthusiasm regarding the purported specificity of iNO: vasodilation by iNO was specific to the lung (without a change in systemic vascular resistance), and within the lung, NO activity was said to be confined spatially and temporally by Hb within the vascular lumen. Underlying these claims were classical views of NO as a short-lived paracrine hormone that acts largely through the heme groups of soluble guanylate cyclase, and whose potential activity is terminated on encountering the hemes of red blood cell (RBC) Hb. These classical views are yielding to a broader paradigm, in which NO-related signaling is achieved through redox-related NO adducts that endow NO synthase products with the ability to act at a distance in space and time from NO synthase itself. Evidence supporting the biological importance of such stable NO adducts is probably strongest for S-nitrosothiols (SNOs), in which NO binds to critical cysteine residues in proteins or peptides. The circulating RBC is a major SNO reservoir, and RBC Hb releases SNO-related bioactivity peripherally on O2 desaturation. These new paradigms describing NO transport also provide a plausible mechanistic understanding of the increasingly recognized peripheral effects of inhaled NO. An explanation for the peripheral actions of inhaled NO is discussed here, and the rationale and results of attempts to exploit the "NO delivery" function of the RBC are reviewed.
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http://dx.doi.org/10.1513/pats.200507-066BGDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658680PMC
April 2006

Redox activation of intracellular calcium release channels (ryanodine receptors) in the sustained phase of hypoxia-induced pulmonary vasoconstriction.

Chest 2005 Dec;128(6 Suppl):556S-558S

Division of Pulmonary, Allergy and Critical Care Medicine, PO Box 3168, Duke University Medical Center, Durham, NC 27710, USA.

Hypoxia-induced pulmonary vasoconstriction (HPV) is an important adaptive process that remains incompletely understood. In preconstricted rat pulmonary arteries (inner diameter, 250 to 400 microm), hypoxia (pO2 approximately 10 mm Hg) induces an initial transient phase and a more slowly developing sustained phase of vasoconstriction. Since the release of calcium ions (Ca2+) from intracellular stores by redox-sensitive intracellular Ca2+ release channels known as ryanodine receptors (RyRs) in pulmonary arterial smooth-muscle cells (PASMCs) may play a role in HPV, and considerable evidence now supports that levels of reactive oxygen species (ROS) are paradoxically increased in PASMC under hypoxia, we investigated whether redox activation of RyRs by ROS may transduce HPV. By reverse transcriptase-polymerase chain reaction, we found that all three RyR isoforms are expressed in rat pulmonary arteries and in PASMCs. The sustained phase, but not the transient phase, of HPV can be prevented by pretreating pulmonary arteries with RyR inhibitors ryanodine (200 micromol/L) or dantrolene (50 micromol/L). The addition of dantrolene, ryanodine or the thiol-reducing agent dithiothreitol (1 mmol/L) during the sustained phase of HPV reversed the hypoxic vasoconstriction. In contrast, the superoxide scavenger nitroblue tetrazolium (500 nmol/L) prevented further hypoxic pulmonary vasoconstriction during the sustained phase of HPV but did not reverse it. Taken together, our data suggest that redox activation of RyRs by ROS has an important role in transducing the sustained contraction of pulmonary arteries under hypoxia.
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http://dx.doi.org/10.1378/chest.128.6_suppl.556SDOI Listing
December 2005

A nitric oxide processing defect of red blood cells created by hypoxia: deficiency of S-nitrosohemoglobin in pulmonary hypertension.

Proc Natl Acad Sci U S A 2005 Oct 3;102(41):14801-6. Epub 2005 Oct 3.

Department of Medicine and Pediatrics, Duke University Medical Center, Durham, NC 27710, USA.

The mechanism by which hypoxia [low partial pressure of O(2) (pO(2))] elicits signaling to regulate pulmonary arterial pressure is incompletely understood. We considered the possibility that, in addition to its effects on smooth muscle, hypoxia may influence pulmonary vascular tone through an effect on RBCs. We report that exposure of native RBCs to sustained hypoxia is accompanied by a buildup of heme iron-nitrosyl (FeNO) species that are deficient in pO(2-)governed intramolecular transfer of NO to cysteine thiol, yielding a deficiency in the vasodilator S-nitrosohemoglobin (SNO-Hb). S-nitrosothiol (SNO)-deficient RBCs produce impaired vasodilator responses in vitro and exaggerated pulmonary vasoconstrictor responses in vivo and are defective in oxygenating the blood. RBCs from hypoxemic patients with elevated pulmonary arterial pressure (PAP) exhibit a similar FeNO/SNO imbalance and are thus deficient in pO(2)-coupled vasoregulation. Chemical restoration of SNO-Hb levels in both animals and patients restores the vasodilator activity of RBCs, and this activity is associated with improved oxygenation and lower PAPs.
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http://dx.doi.org/10.1073/pnas.0506957102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1253588PMC
October 2005
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