scholarly journals A human factor H-binding protein of Bartonella bacilliformis and potential role in serum resistance

2021 ◽  
Author(s):  
Linda D. Hicks ◽  
Shaun Wachter ◽  
Benjamin J. Mason ◽  
Pablo Marin Garrido ◽  
Mason Derendinger ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Vascular Endothelial Cells ◽  
Circulatory System ◽  
Factor H ◽  
Serum Complement ◽  
Serum Factor ◽  
Passenger Domain ◽  
Bartonella Bacilliformis ◽  
Human Host ◽  
Life Threatening Illness

AbstractBartonella bacilliformis is a Gram-negative bacterium and etiologic agent of Carrión’s disease; a potentially life-threatening illness endemic to South America. B. bacilliformis is a facultative parasite that infects human erythrocytes (hemotrophism) and the circulatory system, culminating in a variety of symptoms, including a precipitous drop in hematocrit, angiomatous lesions of the skin (verruga peruana) and persistent bacteremia. Because of its specialized niche, serum complement imposes a continual selective pressure on the pathogen. In this study, we demonstrated the marked serum-resistance phenotype of B. bacilliformis, the role of factor H in serum complement resistance, and binding of host factor H to four membrane-associated polypeptides of ∼131, 119, 60 and 43 kDa by far-western (FW) blots. The ∼119-kDa protein was identified as ABM44634.1 by mass spectrometry; a protein annotated as a 116.5-kDa outer membrane autotransporter (encoded by the BARBAKC583_1133 locus). We designated the protein as factor H-binding protein A (FhbpA). FhbpA possesses three structural motifs common to all autotransporter proteins (i.e., a signal peptide, autotransporter β-barrel domain and passenger domain). Recombinant FhbpA passenger domain, but not the recombinant autotransporter domain, was able to bind human factor H when analyzed by FW blots. Phylogenetic analyses of the passenger domain suggest that it is well-conserved among Bartonella autotransporters, with closest matches from Bartonella schoenbuchensis. Transcriptomic analyses of B. bacilliformis subjected to conditions mimicking the sand fly vector or human host, and infection of human blood or vascular endothelial cells showed maximal expression of fhbpA under human-like conditions and during infection of blood and endothelial cells. Expression during HUVEC infection was significantly higher compared to all other conditions by DESeq2. Surface binding of serum factor H by FhbpA is hypothesized to play a protective role against the alternative pathway of complement fixation during B. bacilliformis infection of the human host.Author SummaryB. bacilliformis is a bacterial pathogen that colonizes the circulatory system of humans, where it can cause a life-threatening illness unless treated. Serum complement is a major effector of innate humoral immunity and a significant obstacle that must be evaded for successful survival and colonization by pathogens, especially those residing in the vasculature. In this study, we examined the serum complement resistance phenotype of B. bacilliformis and identified four membrane-associated proteins that bind serum factor H; a protein used by the host to protect its own tissues from complement activation. One of the proteins was identified by mass spectrometry, characterized, and designated factor H-binding protein A (FhbpA). FhbpA is a predicted autotransporter, and we determined that the translocated “ passenger” domain of the protein is responsible for binding factor H. We also determined that expression of the fhbpA gene was highest during infection of human blood and especially vascular endothelial cells or under conditions that simulate the human host. The results suggest that FhbpA binding of host serum factor H protects the bacterium against complement activation during infection.

Novel control of cAMP-regulated transcription in vascular endothelial cells

2012 ◽  
Vol 40 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Gillian R. Milne ◽  
Timothy M. Palmer ◽  
Stephen J. Yarwood
Keyword(s):  
Endothelial Cells ◽  
Molecular Mechanisms ◽  
Inflammatory Responses ◽  
Vascular Endothelial Cells ◽  
Inflammatory Diseases ◽  
Circulatory System ◽  
Vascular Endothelial ◽  
Protective Mechanisms ◽  
Enhancer Binding Protein ◽  
Developed World

Chronic inflammatory diseases, such as atherosclerosis, are a major cause of death and disability in the developed world. In this respect, although cholesterol obviously plays a predominant role in atherosclerosis, targeting inflammation at lesion sites may be just as important. Indeed, elevated IL-6 (interleukin 6) levels are as strongly associated with coronary heart disease as increased cholesterol. We have been investigating novel cAMP-regulated pathways that combat the action of pro-inflammatory cytokines, such as IL-6 and leptin, in the VECs (vascular endothelial cells) of the circulatory system. In this respect, we have begun to unravel new molecular mechanisms by which the cAMP/Epac1 (exchange protein directly activated by cAMP 1)/Rap1 pathway can initiate a rigorous programme of protective anti-inflammatory responses in VECs. Central to this is the coupling of cAMP elevation to the mobilization of two C/EBP (CCAAT/enhancer-binding protein) family transcription factors, resulting in the induction of the SOCS3 (suppressor of cytokine signalling 3) gene, which attenuates pro-inflammatory cytokine signalling in VECs. These novel ‘protective’ mechanisms of cAMP action will inform the development of the next generation of pharmaceuticals specifically designed to combat endothelial inflammation associated with cardiovascular disease.

scholarly journals Mitogenic Effect of Bartonella bacilliformis on Human Vascular Endothelial Cells and Involvement of GroEL

2003 ◽  
Vol 71 (12) ◽  
pp. 6933-6942 ◽  
Author(s):  
Michael F. Minnick ◽  
Laura S. Smitherman ◽  
D. Scott Samuels
Keyword(s):  
Endothelial Cells ◽  
Vascular Endothelial Cells ◽  
Brdu Incorporation ◽  
Serum Starvation ◽  
Vascular Endothelial ◽  
Multicopy Plasmid ◽  
Bartonella Bacilliformis ◽  
Cell Numbers ◽  
Cell Lysate ◽  
Soluble Cell

ABSTRACT Bartonellae are bacterial pathogens for a wide variety of mammals. In humans, bartonellosis can result in angioproliferative lesions that are potentially life threatening to the patient, including bacillary angiomatosis, bacillary peliosis, and verruga peruana. The results of this study show that Bartonella bacilliformis, the agent of Oroya fever and verruga peruana, produces a proteinaceous mitogen for human vascular endothelial cells (HUVECs) that acts in a dose-dependent fashion in vitro with maximal activity at ≥72 h of exposure and results in a 6- to 20-fold increase in cell numbers relative to controls. The mitogen increases bromodeoxyuridine (BrdU) incorporation into HUVECs by almost twofold relative to controls. The mitogen is sensitive to heat and trypsin but is not affected by the lipopolysaccharide inhibitor polymyxin B. The mitogen does not affect caspase 3 activity in HUVECs undergoing serum starvation-induced apoptosis. The Bartonella mitogen was found in bacterial culture supernatants, the soluble cell lysate fraction, and, to a lesser degree, in insoluble cell fractions of the bacterium. In contrast, soluble cell lysate fractions from closely related B. henselae, although possessing significant mitogenicity for HUVECs, resulted in only about a twofold increase in cell numbers. Biochemical and immunological analyses identified GroEL as a participant in the observed HUVEC mitogenicity. A B. bacilliformis strain containing the intact groES-groEL operon on a multicopy plasmid was generated and used to demonstrate a correlation between HUVEC mitogenicity and GroEL levels in the lysate (r 2 = 0.85). Antiserum to GroEL significantly inhibited mitogenicity of the lysate. Data also show that GroEL is located in the soluble and insoluble fractions (including inner and outer membranes) of the cell and is actively secreted by B. bacilliformis.

scholarly journals No Evidence for Erythro-Myeloid Progenitor-Derived Vascular Endothelial Cells in Multiple Organs

2020 ◽  
Vol 127 (10) ◽  
pp. 1221-1232 ◽  
Author(s):  
Teng Feng ◽  
Zibei Gao ◽  
Shan Kou ◽  
Xinyan Huang ◽  
Zhen Jiang ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
De Novo ◽  
Vascular Endothelial Cells ◽  
Tyrosine Phosphatase ◽  
Circulatory System ◽  
Lineage Tracing ◽  
Genetic Lineage ◽  
Entry Site ◽  
Developmental Origin ◽  
Multiple Organs

Rationale: Endothelial cells are thought to emerge de novo from the mesoderm to form the entire circulatory system. Recently, erythro-myeloid progenitors (EMPs) have been proposed to be another remarkable developmental origin for blood vessels in multiple organs, including the hindbrain, liver, lung, and heart, as demonstrated by lineage tracing studies using different genetic tools. These observations challenge the current consensus that intraembryonic vessels are thought to expand solely by the proliferation of preexisting endothelial cells. Resolution of this controversy over the developmental origin of endothelial cells is crucial for developing future therapeutics for vessel-dependent organ repair and regeneration. Objective: To examine the contribution of EMPs to intraembryonic endothelial cells. Methods and Results: We first used a transgenic mouse expressing a tamoxifen-inducible Mer-iCre fusion protein driven by the Csf1r (colony stimulating factor 1 receptor) promoter. Genetic lineage tracing based on Csf1r-Mer-iCre-Mer showed no contribution of EMPs to brain endothelial cells identified by several markers. We also generated a knock-in mouse line by inserting an internal ribosome entry site-iCre cassette into the 3′ untranslated region of Csf1r gene to further investigate the cellular fates of EMPs. Similarly, we did not find any Csf1r-ires-iCre traced endothelial cells in brain, liver, lung, or heart in development either. Additionally, we found that Kit (KIT proto-oncogene receptor tyrosine kinase) was expressed not only in EMPs but also in embryonic hindbrain endothelial cells. Therefore, Kit promoter–driven recombinase, such as Kit-CreER, is a flawed tool for lineage tracing when examining the contribution of EMPs to hindbrain endothelial cells. We also traced CD45 (protein tyrosine phosphatase receptor type C; Ptprc) + circulating EMPs and did not find any CD45 lineage-derived endothelial cells during development. Conclusions: Our study suggested that EMPs are not the origin of intraembryonic endothelial cells.

The Endothelial Cell and the Factor VIII Bypassing Activity of Prothrombin Complex Concentrate

1988 ◽  
Vol 60 (02) ◽  
pp. 226-229 ◽  
Author(s):  
Jerome M Teitel ◽  
Hong-Yu Ni ◽  
John J Freedman ◽  
M Bernadette Garvey
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Factor Viii ◽  
Prothrombin Complex Concentrate ◽  
Vascular Endothelial Cells ◽  
Vascular Endothelial ◽  
Monolayer Cultures ◽  
Coagulant Activity ◽  
Time Courses ◽  
Privileged Site

SummarySome classical hemophiliacs have a paradoxical hemostatic response to prothrombin complex concentrate (PCC). We hypothesized that vascular endothelial cells (EC) may contribute to this “factor VIII bypassing activity”. When PCC were incubated with suspensions or monolayer cultures of EC, they acquired the ability to partially bypass the defect of factor VIII deficient plasma. This factor VIII bypassing activity distributed with EC and not with the supernatant PCC, and was not a general property of intravascular cells. The effect of PCC was even more dramatic on fixed EC monolayers, which became procoagulant after incubation with PCC. The time courses of association and dissociation of the PCC-derived factor VIII bypassing activity of fixed and viable EC monolayers were both rapid. We conclude that EC may provide a privileged site for sequestration of constituents of PCC which express coagulant activity and which bypass the abnormality of factor VIII deficient plasma.

Alterations in Vascular Endothelial Cell-related Plasma Proteins In Thalassaemic Patients and their Correlation with Clinical Symptoms

1995 ◽  
Vol 74 (04) ◽  
pp. 1045-1049 ◽  
Author(s):  
P Butthep ◽  
A Bunyaratvej ◽  
Y Funahara ◽  
H Kitaguchi ◽  
S Fucharoen ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Immunosorbent Assay ◽  
Plasma Proteins ◽  
Clinical Symptoms ◽  
Vascular Endothelial Cells ◽  
Vascular Endothelial Cell ◽  
Enzyme Linked Immunosorbent Assay ◽  
Vascular Endothelial ◽  
Leg Ulcers

SummaryAn increased level of plasma thrombomodulin (TM) in α- and β- thalassaemia was demonstrated using an enzyme-linked immunosorbent assay (ELISA). Nonsplenectomized patients with β-thalassaemia/ haemoglobin E (BE) had higher levels of TM than splenectomized cases (BE-S). Patients with leg ulcers (BE-LU) were found to have the highest increase in TM level. Appearance of larger platelets in all types of thalassaemic blood was observed indicating an increase in the number of younger platelets. These data indicate that injury of vascular endothelial cells is present in thalassaemic patients.

Modulation of Arachidonic Acid Metabolism in Human Endothelial Cells by Glucocorticoids

1986 ◽  
Vol 55 (03) ◽  
pp. 369-374 ◽  
Author(s):  
Raffaele De Caterina ◽  
Babette B Weksler
Keyword(s):  
Endothelial Cells ◽  
Vascular Endothelial Cells ◽  
Umbilical Vein ◽  
Arachidonic Acid Metabolism ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Prolonged Incubation ◽  
Dependent Inhibition ◽  
Human Thrombin ◽  
Umbilical Vein Endothelial Cells

SummaryTo learn whether glucocorticoids inhibit prostaglandin (PG) production in vascular endothelial cells, we investigated the effects of glucocorticoids on PG synthesis by cultured human umbilical vein endothelial cells (EC). Pretreatment of EC with dexamethasone (DX, 10-9 to 5 x 10-5 M) caused a dose-dependent inhibition of PGI2 production when PG synthesis from endogenous arachidonate was stimulated by human thrombin (0.25-2 U/ml) or ionophore A 23187 (1-5 μM). The inhibition was detectable at 10-7 M DX and maximal at 10-5 M (4.0 ± 0.7 vs. control: 7.7 ± 1.9 ng/ml, mean ± S.D., P <0.01). The production of PGE2 and the release of radiolabelled arachidonate (AA) from prelabelled cells were similarly inhibited. Prolonged incubation of EC with glucocorticoids was required to inhibit PG production or arachidonate release: ranging from 8% inhibition at 5 h to 44% at 38 h. In contrast, prostaglandin formation from exogenous AA was not altered by DX treatment. When thrombin or ionophore-stimulated EC were restimulated with exogenous AA (25 μM), DX-treated cells released more PGI2 than control cells (5.7 ± 0.5 vs. 4.1 ± 0.6 ng/ml, P <0.01). Both the decrease in PGI2 production after thrombin/ionophore and the increase after re-stimulation with AA were blunted in the presence of the protein synthesis inhibitor cycloheximide (0.1-0.2 μg/ml). Thus, incubation of EC with glucocorticoids inhibits PG production at the step of phospholipase activation. The time requirement for these steroid effects and their blunting by cycloheximide are consistent with the induction of regulatory proteins, possibly lipocortins, in endothelial cells.

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