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Characterization of the hemodynamic response function in white matter tracts for event-related fMRI.
Li M, Newton AT, Anderson AW, Ding Z, Gore JC
(2019) Nat Commun 10: 1140
MeSH Terms: Adult, Cerebral Cortex, Cerebrovascular Circulation, Female, Gray Matter, Healthy Volunteers, Hemodynamics, Hemoglobins, Humans, Magnetic Resonance Imaging, Male, Nerve Net, Oxygen, Pattern Recognition, Visual, Stroop Test, White Matter
Show Abstract · Added March 26, 2019
Accurate estimates of the BOLD hemodynamic response function (HRF) are crucial for the interpretation and analysis of event-related functional MRI data. To date, however, there have been no comprehensive measurements of the HRF in white matter (WM) despite increasing evidence that BOLD signals in WM change after a stimulus. We performed an event-related cognitive task (Stroop color-word interference) to measure the HRF in selected human WM pathways. The task was chosen in order to produce robust, distributed centers of activity throughout the cortex. To measure the HRF in WM, fiber tracts were reconstructed between each pair of activated cortical areas. We observed clear task-specific HRFs with reduced magnitudes, delayed onsets and prolonged initial dips in WM tracts compared with activated grey matter, thus calling for significant changes to current standard models for accurately characterizing the HRFs in WM and for modifications of standard methods of analysis of functional imaging data.
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16 MeSH Terms
Molecular Basis for the Evolution of Species-Specific Hemoglobin Capture by Staphylococcus aureus.
Choby JE, Buechi HB, Farrand AJ, Skaar EP, Barber MF
(2018) MBio 9:
MeSH Terms: Animals, Cation Transport Proteins, Evolution, Molecular, Hemoglobins, Host-Pathogen Interactions, Iron, Mutation, Primates, Protein Binding, Species Specificity, Staphylococcus aureus
Show Abstract · Added April 7, 2019
Metals are a limiting resource for pathogenic bacteria and must be scavenged from host proteins. Hemoglobin provides the most abundant source of iron in the human body and is required by several pathogens to cause invasive disease. However, the consequences of hemoglobin evolution for bacterial nutrient acquisition remain unclear. Here we show that the α- and β-globin genes exhibit strikingly parallel signatures of adaptive evolution across simian primates. Rapidly evolving sites in hemoglobin correspond to binding interfaces of IsdB, a bacterial hemoglobin receptor harbored by pathogenic Using an evolution-guided experimental approach, we demonstrate that the divergence between primates and staphylococcal isolates governs hemoglobin recognition and bacterial growth. The reintroduction of putative adaptive mutations in α- or β-globin proteins was sufficient to impair binding, providing a mechanism for the evolution of disease resistance. These findings suggest that bacterial hemoprotein capture has driven repeated evolutionary conflicts with hemoglobin during primate descent. During infection, bacteria must steal metals, including iron, from the host tissue. Therefore, pathogenic bacteria have evolved metal acquisition systems to overcome the elaborate processes mammals use to withhold metal from pathogens. uses IsdB, a hemoglobin receptor, to thieve iron-containing heme from hemoglobin within human blood. We find evidence that primate hemoglobin has undergone rapid evolution at protein surfaces contacted by IsdB. Additionally, variation in the hemoglobin sequences among primates, or variation in IsdB of related staphylococci, reduces bacterial hemoglobin capture. Together, these data suggest that has evolved to recognize human hemoglobin in the face of rapid evolution at the IsdB binding interface, consistent with repeated evolutionary conflicts in the battle for iron during host-pathogen interactions.
Copyright © 2018 Choby et al.
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11 MeSH Terms
Ascorbic acid attenuates endothelial permeability triggered by cell-free hemoglobin.
Kuck JL, Bastarache JA, Shaver CM, Fessel JP, Dikalov SI, May JM, Ware LB
(2018) Biochem Biophys Res Commun 495: 433-437
MeSH Terms: Antioxidants, Ascorbic Acid, Capillary Permeability, Endothelium, Vascular, Hemoglobins, Human Umbilical Vein Endothelial Cells, Humans, Sepsis
Show Abstract · Added March 14, 2018
BACKGROUND - Increased endothelial permeability is central to shock and organ dysfunction in sepsis but therapeutics targeted to known mediators of increased endothelial permeability have been unsuccessful in patient studies. We previously reported that cell-free hemoglobin (CFH) is elevated in the majority of patients with sepsis and is associated with organ dysfunction, poor clinical outcomes and elevated markers of oxidant injury. Others have shown that Vitamin C (ascorbate) may have endothelial protective effects in sepsis. In this study, we tested the hypothesis that high levels of CFH, as seen in the circulation of patients with sepsis, disrupt endothelial barrier integrity.
METHODS - Human umbilical vein endothelial cells (HUVEC) were grown to confluence and treated with CFH with or without ascorbate. Monolayer permeability was measured by Electric Cell-substrate Impedance Sensing (ECIS) or transfer of C-inulin. Viability was measured by trypan blue exclusion. Intracellular ascorbate was measured by HPLC.
RESULTS - CFH increased permeability in a dose- and time-dependent manner with 1 mg/ml of CFH increasing inulin transfer by 50% without affecting cell viability. CFH (1 mg/ml) also caused a dramatic reduction in intracellular ascorbate in the same time frame (1.4 mM without CFH, 0.23 mM 18 h after 1 mg/ml CFH, p < 0.05). Pre-treatment of HUVECs with ascorbate attenuated CFH induced permeability.
CONCLUSIONS - CFH increases endothelial permeability in part through depletion of intracellular ascorbate. Supplementation of ascorbate can attenuate increases in permeability mediated by CFH suggesting a possible therapeutic approach in sepsis.
Copyright © 2017 Elsevier Inc. All rights reserved.
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8 MeSH Terms
Cell-Free Hemoglobin-mediated Increases in Vascular Permeability. A Novel Mechanism of Primary Graft Dysfunction and a New Therapeutic Target.
Shaver CM, Wickersham N, McNeil JB, Nagata H, Sills G, Kuck JL, Janz DR, Bastarache JA, Ware LB
(2017) Ann Am Thorac Soc 14: S251-S252
MeSH Terms: Acetaminophen, Capillary Permeability, Endothelial Cells, Hemoglobins, Humans, Lung, Lung Transplantation, Primary Graft Dysfunction
Show Abstract · Added May 31, 2018
RATIONALE - Cell-free hemoglobin (CFH) is a potent oxidant associated with poor clinical outcomes in a variety of clinical settings. Recent studies suggest that acetaminophen (APAP), a specific hemoprotein reductant, can abrogate CFH-mediated oxidative injury and organ dysfunction. Preoperative plasma CFH levels are independently associated with primary graft dysfunction (PGD) after lung transplant ( 1 ).
OBJECTIVES - Our objectives were to determine whether CFH would increase lung vascular permeability in the isolated perfused human lung and whether APAP would limit these effects.
METHODS - Human lungs declined for transplant were inflated and perfused with Dulbecco's modified Eagle medium/5% albumin at a pulmonary artery pressure of 8-12 mm Hg. After steady state was achieved, CFH (100 mg/dl) was added to the perfusate ± APAP (15 μg/ml). Lung permeability was measured by continuous monitoring of lung weight gain and by extravasation of Evans blue dye-labeled albumin from the vasculature into bronchoalveolar lavage. To test the mechanism of increased permeability, human pulmonary microvascular endothelial cells were exposed to CFH (0.5 mg/ml) ± APAP (160 μM) for 24 hours and permeability was assessed by electrical cell-substrate impedance sensing.
MEASUREMENT AND MAIN RESULTS - In the isolated perfused human lung, CFH increased lung permeability over 2 hours compared with control lungs (12% vs. 2% weight gain from baseline, P = 0.03). Increased vascular permeability was confirmed by a 4.8-fold increase in Evans blue dye-labeled albumin in the airspace compared with control lungs. Pretreatment with APAP prevented lung weight gain (P = 0.06 vs. CFH). In human pulmonary microvascular endothelial cells, CFH increased monolayer permeability (P = 0.03 vs. control), and this was attenuated by APAP (P = 0.045 vs. CFH).
CONCLUSIONS - Circulating CFH increases vascular permeability in the isolated perfused human lung and paracellular permeability in lung microvascular endothelial cells. These effects may explain the association of plasma CFH levels with PGD. The hemoprotein reductant APAP attenuates the effects of CFH and merits further exploration as a potential therapy for PGD prevention.
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MeSH Terms
Defining the complex phenotype of severe systemic loxoscelism using a large electronic health record cohort.
Robinson JR, Kennedy VE, Doss Y, Bastarache L, Denny J, Warner JL
(2017) PLoS One 12: e0174941
MeSH Terms: Adolescent, Animals, Bilirubin, Brown Recluse Spider, Case-Control Studies, Child, Cross-Sectional Studies, Disseminated Intravascular Coagulation, Electronic Health Records, Female, Hemoglobins, Hemolysis, Humans, L-Lactate Dehydrogenase, Male, Phenotype, Retrospective Studies, Spider Bites, Spider Venoms, Survival Analysis, Young Adult
Show Abstract · Added November 8, 2017
OBJECTIVE - Systemic loxoscelism is a rare illness resulting from the bite of the recluse spider and, in its most severe form, can lead to widespread hemolysis, coagulopathy, and death. We aim to describe the clinical features and outcomes of the largest known cohort of individuals with moderate to severe loxoscelism.
METHODS - We performed a retrospective, cross sectional study from January 1, 1995, to December 31, 2015, at a tertiary-care academic medical center, to determine individuals with clinical records consistent with moderate to severe loxoscelism. Age-, sex-, and race-matched controls were compared. Demographics, clinical characteristics, laboratory measures, and outcomes of individuals with loxoscelism are described. Case and control groups were compared with descriptive statistics and phenome-wide association study (PheWAS).
RESULTS - During the time period, 57 individuals were identified as having moderate to severe loxoscelism. Of these, only 33% had an antecedent spider bite documented. Median age of individuals diagnosed with moderate to severe loxoscelism was 14 years old (IQR 9.0-24.0 years). PheWAS confirmed associations of systemic loxoscelism with 29 other phenotypes, e.g., rash, hemolytic anemia, and sepsis. Hemoglobin level dropped an average of 3.1 g/dL over an average of 2.0 days (IQR 2.0-6.0). Lactate dehydrogenase and total bilirubin levels were on average over two times their upper limit of normal values. Eighteen individuals of 32 tested had a positive direct antiglobulin (Coombs') test. Mortality was 3.5% (2/57 individuals).
CONCLUSION - Systemic loxoscelism is a rare but devastating process with only a minority of patients recalling the toxic exposure; hemolysis reaches a peak at 2 days after admission, with some cases taking more than a week before recovery. In endemic areas, suspicion for systemic loxoscelism should be high in individuals, especially children and younger adults, presenting with a cutaneous ulcer and hemolysis or coagulopathy, even in the absence of a bite exposure history.
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21 MeSH Terms
Competing for Iron: Duplication and Amplification of the isd Locus in Staphylococcus lugdunensis HKU09-01 Provides a Competitive Advantage to Overcome Nutritional Limitation.
Heilbronner S, Monk IR, Brozyna JR, Heinrichs DE, Skaar EP, Peschel A, Foster TJ
(2016) PLoS Genet 12: e1006246
MeSH Terms: DNA Copy Number Variations, Endocarditis, Bacterial, Gene Duplication, Genetic Loci, Heme, Hemoglobins, Humans, Iron, Iron-Regulatory Proteins, Staphylococcal Infections, Staphylococcus lugdunensis, Surface Properties
Show Abstract · Added April 8, 2017
Staphylococcus lugdunensis is a coagulase negative bacterial pathogen that is particularly associated with severe cases of infectious endocarditis. Unique amongst the coagulase-negative staphylococci, S. lugdunensis harbors an iron regulated surface determinant locus (isd). This locus facilitates the acquisition of heme as a source of nutrient iron during infection and allows iron limitation caused by "nutritional immunity" to be overcome. The isd locus is duplicated in S. lugdunensis HKU09-01 and we show here that the duplication is intrinsically unstable and undergoes accordion-like amplification and segregation leading to extensive isd copy number variation. Amplification of the locus increased the level of expression of Isd proteins and improved binding of hemoglobin to the cell surface of S. lugdunensis. Furthermore, Isd overexpression provided an advantage when strains were competing for a limited amount of hemoglobin as the sole source of iron. Gene duplications and amplifications (GDA) are events of fundamental importance for bacterial evolution and are frequently associated with antibiotic resistance in many species. As such, GDAs are regarded as evolutionary adaptions to novel selective pressures in hostile environments pointing towards a special importance of isd for S. lugdunensis. For the first time we show an example of a GDA that involves a virulence factor of a Gram-positive pathogen and link the GDA directly to a competitive advantage when the bacteria were struggling with selective pressures mimicking "nutritional immunity".
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12 MeSH Terms
Exome Genotyping Identifies Pleiotropic Variants Associated with Red Blood Cell Traits.
Chami N, Chen MH, Slater AJ, Eicher JD, Evangelou E, Tajuddin SM, Love-Gregory L, Kacprowski T, Schick UM, Nomura A, Giri A, Lessard S, Brody JA, Schurmann C, Pankratz N, Yanek LR, Manichaikul A, Pazoki R, Mihailov E, Hill WD, Raffield LM, Burt A, Bartz TM, Becker DM, Becker LC, Boerwinkle E, Bork-Jensen J, Bottinger EP, O'Donoghue ML, Crosslin DR, de Denus S, Dubé MP, Elliott P, Engström G, Evans MK, Floyd JS, Fornage M, Gao H, Greinacher A, Gudnason V, Hansen T, Harris TB, Hayward C, Hernesniemi J, Highland HM, Hirschhorn JN, Hofman A, Irvin MR, Kähönen M, Lange E, Launer LJ, Lehtimäki T, Li J, Liewald DC, Linneberg A, Liu Y, Lu Y, Lyytikäinen LP, Mägi R, Mathias RA, Melander O, Metspalu A, Mononen N, Nalls MA, Nickerson DA, Nikus K, O'Donnell CJ, Orho-Melander M, Pedersen O, Petersmann A, Polfus L, Psaty BM, Raitakari OT, Raitoharju E, Richard M, Rice KM, Rivadeneira F, Rotter JI, Schmidt F, Smith AV, Starr JM, Taylor KD, Teumer A, Thuesen BH, Torstenson ES, Tracy RP, Tzoulaki I, Zakai NA, Vacchi-Suzzi C, van Duijn CM, van Rooij FJ, Cushman M, Deary IJ, Velez Edwards DR, Vergnaud AC, Wallentin L, Waterworth DM, White HD, Wilson JG, Zonderman AB, Kathiresan S, Grarup N, Esko T, Loos RJ, Lange LA, Faraday N, Abumrad NA, Edwards TL, Ganesh SK, Auer PL, Johnson AD, Reiner AP, Lettre G
(2016) Am J Hum Genet 99: 8-21
MeSH Terms: African Americans, Allelic Imbalance, Erythrocyte Indices, Erythrocytes, Erythropoiesis, Exome, Gene Frequency, Genetic Pleiotropy, Genetic Variation, Genotype, Hematocrit, Hemoglobins, Humans, Quantitative Trait Loci
Show Abstract · Added April 26, 2017
Red blood cell (RBC) traits are important heritable clinical biomarkers and modifiers of disease severity. To identify coding genetic variants associated with these traits, we conducted meta-analyses of seven RBC phenotypes in 130,273 multi-ethnic individuals from studies genotyped on an exome array. After conditional analyses and replication in 27,480 independent individuals, we identified 16 new RBC variants. We found low-frequency missense variants in MAP1A (rs55707100, minor allele frequency [MAF] = 3.3%, p = 2 × 10(-10) for hemoglobin [HGB]) and HNF4A (rs1800961, MAF = 2.4%, p < 3 × 10(-8) for hematocrit [HCT] and HGB). In African Americans, we identified a nonsense variant in CD36 associated with higher RBC distribution width (rs3211938, MAF = 8.7%, p = 7 × 10(-11)) and showed that it is associated with lower CD36 expression and strong allelic imbalance in ex vivo differentiated human erythroblasts. We also identified a rare missense variant in ALAS2 (rs201062903, MAF = 0.2%) associated with lower mean corpuscular volume and mean corpuscular hemoglobin (p < 8 × 10(-9)). Mendelian mutations in ALAS2 are a cause of sideroblastic anemia and erythropoietic protoporphyria. Gene-based testing highlighted three rare missense variants in PKLR, a gene mutated in Mendelian non-spherocytic hemolytic anemia, associated with HGB and HCT (SKAT p < 8 × 10(-7)). These rare, low-frequency, and common RBC variants showed pleiotropy, being also associated with platelet, white blood cell, and lipid traits. Our association results and functional annotation suggest the involvement of new genes in human erythropoiesis. We also confirm that rare and low-frequency variants play a role in the architecture of complex human traits, although their phenotypic effect is generally smaller than originally anticipated.
Copyright © 2016 American Society of Human Genetics. All rights reserved.
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14 MeSH Terms
Cell-free hemoglobin: a novel mediator of acute lung injury.
Shaver CM, Upchurch CP, Janz DR, Grove BS, Putz ND, Wickersham NE, Dikalov SI, Ware LB, Bastarache JA
(2016) Am J Physiol Lung Cell Mol Physiol 310: L532-41
MeSH Terms: Acute Lung Injury, Alveolar Epithelial Cells, Animals, Biomarkers, Cell Line, Cell Membrane Permeability, Cytokines, Hemoglobins, Humans, Lipopolysaccharides, Lung, Mice, Inbred C57BL, Respiratory Distress Syndrome, Adult
Show Abstract · Added February 17, 2016
Patients with the acute respiratory distress syndrome (ARDS) have elevated levels of cell-free hemoglobin (CFH) in the air space, but the contribution of CFH to the pathogenesis of acute lung injury is unknown. In the present study, we demonstrate that levels of CFH in the air space correlate with measures of alveolar-capillary barrier dysfunction in humans with ARDS (r = 0.89, P < 0.001) and in mice with ventilator-induced acute lung injury (r = 0.89, P < 0.001). To investigate the specific contribution of CFH to ARDS, we studied the impact of purified CFH in the mouse lung and on cultured mouse lung epithelial (MLE-12) cells. Intratracheal delivery of CFH in mice causes acute lung injury with air space inflammation and alveolar-capillary barrier disruption. Similarly, in MLE-12 cells, CFH increases proinflammatory cytokine expression and increases paracellular permeability as measured by electrical cell-substrate impedance sensing. Next, to determine whether these effects are mediated by the iron-containing heme moiety of CFH, we treated mice with intratracheal hemin, the chloride salt of heme, and found that hemin was sufficient to increase alveolar permeability but failed to induce proinflammatory cytokine expression or epithelial cell injury. Together, these data identify CFH in the air space as a previously unrecognized driver of lung epithelial injury in human and experimental ARDS and suggest that CFH and hemin may contribute to ARDS through different mechanisms. Interventions targeting CFH and heme in the air space could provide a new therapeutic approach for ARDS.
Copyright © 2016 the American Physiological Society.
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13 MeSH Terms
Ferric pyrophosphate citrate administered via dialysate reduces erythropoiesis-stimulating agent use and maintains hemoglobin in hemodialysis patients.
Gupta A, Lin V, Guss C, Pratt R, Ikizler TA, Besarab A
(2015) Kidney Int 88: 1187-94
MeSH Terms: Adult, Aged, Dialysis Solutions, Diphosphates, Double-Blind Method, Female, Hematinics, Hemoglobins, Humans, Iron, Male, Middle Aged, Renal Dialysis, Trace Elements
Show Abstract · Added August 5, 2015
Ferric pyrophosphate citrate (FPC) is a water-soluble iron salt administered via dialysate to supply iron directly to transferrin. The PRIME study tested whether treatment with FPC could reduce prescribed erythropoiesis-stimulating agent (ESA) use and maintain hemoglobin in hemodialysis patients. This 9-month, randomized, placebo-controlled, double-blind, multicenter clinical study included 103 patients undergoing hemodialysis 3-4 times weekly. The FPC group received dialysate containing 2 μmol/l of iron. The placebo group received standard dialysate. A blinded central anemia management group facilitated ESA dose adjustments. Intravenous iron was administered according to the approved indication when ferritin levels fell below 200 μg/l. The primary end point was the percentage change from baseline in prescribed ESA dose at end of treatment. Secondary end points included intravenous iron use and safety. At the end of treatment, there was a significant 35% reduction in prescribed ESA dose in FPC-treated patients compared with placebo. The FPC patients used 51% less intravenous iron than placebo. Adverse and serious adverse events were similar in both groups. Thus, FPC delivered via dialysate significantly reduces the prescribed ESA dose and the amount of intravenous iron needed to maintain hemoglobin in chronic hemodialysis patients.
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14 MeSH Terms
Hepcidin-ferroportin axis controls toll-like receptor 4 dependent macrophage inflammatory responses in human atherosclerotic plaques.
Habib A, Polavarapu R, Karmali V, Guo L, Van Dam R, Cheng Q, Akahori H, Saeed O, Nakano M, Pachura K, Hong CC, Shin E, Kolodgie F, Virmani R, Finn AV
(2015) Atherosclerosis 241: 692-700
MeSH Terms: Animals, Antigens, CD, Antigens, Differentiation, Myelomonocytic, Cation Transport Proteins, Foam Cells, Haptoglobins, Hemoglobins, Hepcidins, Humans, Inflammation, Iron, Lipopolysaccharides, Lipoproteins, LDL, Macrophages, Macrophages, Peritoneal, Male, Membrane Microdomains, Mice, Mice, Inbred C57BL, Mice, Knockout, Myeloid Differentiation Factor 88, Plaque, Atherosclerotic, Receptors, Cell Surface, Signal Transduction, Toll-Like Receptor 4, Tumor Necrosis Factor-alpha
Show Abstract · Added July 7, 2015
OBJECTIVES - Toll-like Receptor 4 (TLR4) is implicated in modulating inflammatory cytokines though its role in atherosclerosis remains uncertain. We have recently described a non-foam cell macrophage phenotype driven by ingestion of hemoglobin:haptoglobin complexes (HH), via the scavenger receptor CD163, characterized by reduced inflammatory cytokine production. In this study, we examined the role of iron metabolism in modulating TLR4 signaling in these cells.
METHODS AND RESULTS - Areas in human atherosclerotic plaque with non-foam cell, CD163 positive macrophages demonstrated reduced expression of tumor necrosis factor alpha (TNF-α) and interferon-beta (INF-β) compared to foam cells. Human macrophages differentiated in hemoglobin:haptoglobin (HH) complexes expressed the CD163 positive non-foam cell phenotype and demonstrated significantly less TNF-α and INF-β compared to control macrophages when exposed to oxidized LDL (oxLDL) or lipopolysaccharide (LPS). LPS stimulated expression of TNF-α and INF-β could be restored in HH macrophages by pretreatment with hepcidin, an endogenous suppressor of ferroportin1 (FPN), or by genetic suppression of FPN in macrophages derived from myeloid specific FPN knockout mice. LPS stimulated control macrophages demonstrated increase in TLR4 trafficking to lipid rafts; this response was suppressed in HH macrophages but was restored upon pretreatment with hepcidin. Using a pharmacologic hepcidin suppressor, we observed a decrease in cytokine expression and TLR4-lipid raft trafficking in LPS-stimulated in a murine macrophage model.
CONCLUSION - TLR4 dependent macrophage signaling is controlled via hepcidin-ferroportin1 axis by influencing TLR4-lipid raft interactions. Pharmacologic manipulation of iron metabolism may represent a promising approach to limiting TLR4-mediated inflammatory responses.
Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
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26 MeSH Terms