scholarly journals β-blockers Reverse Agonist-Induced β2-AR Downregulation Regardless of Their Signaling Profile

2020 ◽  
Vol 21 (2) ◽  
pp. 512
Author(s):  
Sonia Maccari ◽  
Vanessa Vezzi ◽  
Federica Barbagallo ◽  
Tonino Stati ◽  
Barbara Ascione ◽  
...  
Keyword(s):  
Cell Surface ◽  
Human Lymphocytes ◽  
Cell Types ◽  
Hek293 Cells ◽  
Enzyme Linked Immunosorbent Assay ◽  
Mrna Levels ◽  
Receptor Density ◽  
Biased Agonism ◽  
Β Blocker ◽  
Β Blockers

Altered β-adrenergic receptor (β-AR) density has been reported in cells, animals, and humans receiving β-blocker treatment. In some cases, β-AR density is upregulated, but in others, it is unaffected or even reduced. Collectively, these results would imply that changes in β-AR density and β-blockade are not related. However, it has still not been clarified whether the effects of β-blockers on receptor density are related to their ability to activate different β-AR signaling pathways. To this aim, five clinically relevant β-blockers endowed with inverse, partial or biased agonism at the β2-AR were evaluated for their effects on β2-AR density in both human embryonic kidney 293 (HEK293) cells expressing exogenous FLAG-tagged human β2-ARs and human lymphocytes expressing endogenous β2-ARs. Cell surface β2-AR density was measured by enzyme-linked immunosorbent assay (ELISA) and flow cytometry. Treatment with propranolol, carvedilol, pindolol, sotalol, or timolol did not induce any significant change in surface β2-AR density in both HEK293 cells and human lymphocytes. On the contrary, treatment with the β-AR agonist isoproterenol reduced the number of cell surface β2-ARs in the tested cell types without affecting β2-AR-mRNA levels. Isoproterenol-induced effects on receptor density were completely antagonized by β-blocker treatment. In conclusion, the agonistic activity of β-blockers does not exert an important effect on short-term regulation of β2-AR density.

scholarly journals Cell shape and plasma membrane alterations after static magnetic fields exposure

10.4081/840 ◽  
2009 ◽  
Vol 47 (4) ◽  
pp. 299 ◽  
Author(s):  
A Chionna ◽  
M Dwikat ◽  
E Panzarini ◽  
B Tenuzzo ◽  
EC Carlà ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Magnetic Fields ◽  
Cell Surface ◽  
Cell Shape ◽  
Biological Effects ◽  
Human Lymphocytes ◽  
Cell Types ◽  
Continuous Exposure ◽  
U937 Cells ◽  
Static Magnetic Fields

The biological effects of static magnetic fields (MFs) with intensity of 6 mT were investigated in lymphocytes and U937 cells in the presence or absence of apoptosis-inducing drugs by transmission (TEM) and scanning (SEM) electron microscopy. Lectin cytochemistry of ConA-FITC conjugates was used to analyze plasma membrane structural modifications. Static MFs modified cell shape, plasma membrane and increased the level of intracellular [Ca++] which plays an antiapoptotic role in both cell types. Modifications induced by the exposure to static MFs were irrespective of the presence or absence of apoptotic drugs or the cell type. Abundant lamellar-shaped microvilli were observed upon 24 hrs of continuous exposure to static MFs in contrast to the normally rough surface of U937 cells having numerous short microvilli. Conversely, lymphocytes lost their round shape and became irregularly elongated; lamellar shaped microvilli were found when cells were simultaneosly exposed to static MFs and apoptosis-inducing drugs. In our experiments, static MFs reduced the smoothness of the cell surface and partially impeded changes in distribution of cell surface glycans, both features being typical of apoptotic cells. Cell shape and plasma membrane structure modifications upon static MFs exposure were time-dependent. Lamellar microvilli were clearly observed before the distortion of cell shape, which was found at long times of exposure. MFs exposure promoted the rearrangement of F-actin filaments which, in turn, could be responsible for the cell surface modifications. Here we report data that support biological effects of static MFs on U937 cells and human lymphocytes. However, the involvement of these modifications in the onset of diseases needs to be further elucidated.

scholarly journals Induction of Cardiac Fibrosis by β-Blocker in G Protein-independent and G Protein-coupled Receptor Kinase 5/β-Arrestin2-dependent Signaling Pathways

2012 ◽  
Vol 287 (42) ◽  
pp. 35669-35677 ◽  
Author(s):  
Michio Nakaya ◽  
Satsuki Chikura ◽  
Kenji Watari ◽  
Natsumi Mizuno ◽  
Koji Mochinaga ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
G Protein ◽  
Adrenergic Receptor ◽  
Cardiac Fibrosis ◽  
Receptor Kinase ◽  
Biased Agonism ◽  
Β Blocker ◽  
Β Blockers ◽  
G Protein Coupled ◽  
Dependent Pathway

G-protein coupled receptors (GPCRs) have long been known as receptors that activate G protein-dependent cellular signaling pathways. In addition to the G protein-dependent pathways, recent reports have revealed that several ligands called “biased ligands” elicit G protein-independent and β-arrestin-dependent signaling through GPCRs (biased agonism). Several β-blockers are known as biased ligands. All β-blockers inhibit the binding of agonists to the β-adrenergic receptors. In addition to β-blocking action, some β-blockers are reported to induce cellular responses through G protein-independent and β-arrestin-dependent signaling pathways. However, the physiological significance induced by the β-arrestin-dependent pathway remains much to be clarified in vivo. Here, we demonstrate that metoprolol, a β1-adrenergic receptor-selective blocker, could induce cardiac fibrosis through a G protein-independent and β-arrestin2-dependent pathway. Metoprolol, a β-blocker, increased the expression of fibrotic genes responsible for cardiac fibrosis in cardiomyocytes. Furthermore, metoprolol induced the interaction between β1-adrenergic receptor and β-arrestin2, but not β-arrestin1. The interaction between β1-adrenergic receptor and β-arrestin2 by metoprolol was impaired in the G protein-coupled receptor kinase 5 (GRK5)-knockdown cells. Metoprolol-induced cardiac fibrosis led to cardiac dysfunction. However, the metoprolol-induced fibrosis and cardiac dysfunction were not evoked in β-arrestin2- or GRK5-knock-out mice. Thus, metoprolol is a biased ligand that selectively activates a G protein-independent and GRK5/β-arrestin2-dependent pathway, and induces cardiac fibrosis. This study demonstrates the physiological importance of biased agonism, and suggests that G protein-independent and β-arrestin-dependent signaling is a reason for the diversity of the effectiveness of β-blockers.

scholarly journals Probing the binding specificities of human Siglecs by cell-based glycan arrays

2021 ◽  
Vol 118 (17) ◽  
pp. e2026102118
Author(s):  
Christian Büll ◽  
Rebecca Nason ◽  
Lingbo Sun ◽  
Julie Van Coillie ◽  
Daniel Madriz Sørensen ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Cell Surface ◽  
Immune Cell ◽  
Late Onset ◽  
Cell Types ◽  
Hek293 Cells ◽  
Cell Functions ◽  
Binding Epitope ◽  
Sialic Acid Binding ◽  
Complex Glycan

Siglecs are a family of sialic acid–binding receptors expressed by cells of the immune system and a few other cell types capable of modulating immune cell functions upon recognition of sialoglycan ligands. While human Siglecs primarily bind to sialic acid residues on diverse types of glycoproteins and glycolipids that constitute the sialome, their fine binding specificities for elaborated complex glycan structures and the contribution of the glycoconjugate and protein context for recognition of sialoglycans at the cell surface are not fully elucidated. Here, we generated a library of isogenic human HEK293 cells with combinatorial loss/gain of individual sialyltransferase genes and the introduction of sulfotransferases for display of the human sialome and to dissect Siglec interactions in the natural context of glycoconjugates at the cell surface. We found that Siglec-4/7/15 all have distinct binding preferences for sialylated GalNAc-type O-glycans but exhibit selectivity for patterns of O-glycans as presented on distinct protein sequences. We discovered that the sulfotransferase CHST1 drives sialoglycan binding of Siglec-3/8/7/15 and that sulfation can impact the preferences for binding to O-glycan patterns. In particular, the branched Neu5Acα2–3(6-O-sulfo)Galβ1–4GlcNAc (6′-Su-SLacNAc) epitope was discovered as the binding epitope for Siglec-3 (CD33) implicated in late-onset Alzheimer’s disease. The cell-based display of the human sialome provides a versatile discovery platform that enables dissection of the genetic and biosynthetic basis for the Siglec glycan interactome and other sialic acid–binding proteins.

Regulation of P2X7nucleotide receptor function in human monocytes by extracellular ions and receptor density

2001 ◽  
Vol 280 (4) ◽  
pp. C943-C953 ◽  
Author(s):  
Lalitha Gudipaty ◽  
Benjamin D. Humphreys ◽  
Gary Buell ◽  
George R. Dubyak
Keyword(s):  
Cell Surface ◽  
Human Blood ◽  
Pore Formation ◽  
Cell Types ◽  
Receptor Activation ◽  
Receptor Expression ◽  
Receptor Protein ◽  
Receptor Subtype ◽  
Mrna Levels ◽  
Blood Monocytes

P2X receptors function as ATP-gated cation channels. The P2X7receptor subtype is distinguished from other P2X family members by a very low affinity for extracellular ATP (millimolar EC50) and its ability to trigger induction of nonselective pores on repeated or prolonged stimulation. Previous studies have indicated that certain P2X7receptor-positive cell types, such as human blood monocytes and murine thymocytes, lack this pore-forming response. In the present study we compared pore formation in response to P2X7receptor activation in human blood monocytes with that in macrophages derived from these monocytes by in vitro tissue culture. ATP induced nonselective pores in macrophages but not in freshly isolated monocytes when both cell types were identically stimulated in standard NaCl-based salines. However, ion substitution studies revealed that replacement of extracellular Na+and Cl−with K+and nonhalide anions strongly facilitated ATP-dependent pore formation in monocytes. These ionic conditions also resulted in increased agonist affinity, such that 30–100 μM ATP was sufficient for activation of nonselective pores by P2X7receptors. Comparison of P2X7receptor expression in blood monocytes with that in macrophages indicated no differences in steady-state receptor mRNA levels but significant increases (up to 10-fold) in the amount of immunoreactive P2X7receptor protein at the cell surface of macrophages. Thus ability of ATP to activate nonselective pores in cells that natively express P2X7receptors can be modulated by receptor subunit density at the cell surface and ambient levels of extracellular Na+and Cl−. These mechanisms may prevent adventitious P2X7receptor activation in monocytes until these proinflammatory leukocytes migrate to extravascular sites of tissue damage.

The organization of cell surface membrane domains

1989 ◽  
Vol 47 ◽  
pp. 804-805
Author(s):  
Michael Edidin
Keyword(s):  
Cell Surface ◽  
Membrane Lipids ◽  
Surface Membrane ◽  
Lateral Diffusion ◽  
Cell Types ◽  
Membrane Domains ◽  
Membrane Biology ◽  
Morphological Polarity ◽  
Discrete Domains ◽  
Membrane Components

Cell surface membranes are based on a fluid lipid bilayer and models of the membranes' organization have emphasised the possibilities for lateral motion of membrane lipids and proteins within the bilayer. Two recent trends in cell and membrane biology make us consider ways in which membrane organization works against its inherent fluidity, localizing both lipids and proteins into discrete domains. There is evidence for such domains, even in cells without obvious morphological polarity and organization [Table 1]. Cells that are morphologically polarised, for example epithelial cells, raise the issue of membrane domains in an accute form.The technique of fluorescence photobleaching and recovery, FPR, was developed to measure lateral diffusion of membrane components. It has also proven to be a powerful tool for the analysis of constraints to lateral mobility. FPR resolves several sorts of membrane domains, all on the micrometer scale, in several different cell types.

The Effects of Vitamin K1 and Warfarin on Prothrombin Expression in Human Hepatoblastoma (HepG2) Cells

1992 ◽  
Vol 68 (01) ◽  
pp. 040-047 ◽  
Author(s):  
C Scott Jamison ◽  
Bryan F Burkey ◽  
Sandra J Friezner Degen
Keyword(s):  
Total Protein ◽  
Hepg2 Cells ◽  
Enzyme Linked Immunosorbent Assay ◽  
Response Analysis ◽  
Secreted Protein ◽  
Mrna Levels ◽  
Vitamin K1 ◽  
Maximal Increase ◽  
Protein Levels ◽  
Warfarin Treatment

SummaryCultures of human hepatoblastoma (HepG2) cells were treated with vitamin K1 or warfarin and prothrombin antigen and mRNA levels were determined. With 3 and 6 h of 10 µg vitamin K1 treatment secreted prothrombin antigen levels, relative to total secreted protein levels, were increased 1.5-fold and 2.1-fold, respectively, over ethanol-treated control levels as determined by an enzyme-linked immunosorbent assay. Dose-response analysis with 3 h of 25 µg/ml vitamin K1 treatment demonstrated a maximal increase of 2.0-fold in secreted prothrombin antigen levels, relative to total secreted protein levels, over ethanol-treated control levels. Pulse-chase analysis with 35S-methionine and immunoprecipitation of 35S-labelled prothrombin demonstrated that, with vitamin K1 treatment (25 µg/ml, 3 h), the rate of prothrombin secretion increased approximately 2-fold and the total amount (intra- and extracellular) of prothrombin synthesized increased approximately 50% over ethanol-treated control levels. Warfarin treatment (1, 5, or 10 µg/ml, 24 h) resulted in decreases in secreted prothrombin antigen levels, relative to total protein levels to approximately 85%, 87% or 81% of ethanol-treated control levels. Analysis of total RNA isolated from these cultures by Northern and solution hybridization techniques demonstrated that prothrombin mRNA was approximately 2.1 kb and that neither vitamin K1 nor warfarin treatment affected the quantity of prothrombin mRNA (ranging from 240–350 prothrombin mRNA molecules per cell). These results demonstrate that vitamin K1 and warfarin, in addition to effects on γ-carboxylation, affect prothrombin synthesis post-transcriptionally, perhaps influencing translation, post-translational processing and/or secretion mechanisms.

Expression of P2X7purinoceptors on human lymphocytes and monocytes: evidence for nonfunctional P2X7receptors

2000 ◽  
Vol 279 (4) ◽  
pp. C1189-C1197 ◽  
Author(s):  
B. J. Gu ◽  
W. Y. Zhang ◽  
L. J. Bendall ◽  
I. P. Chessell ◽  
G. N. Buell ◽  
...  
Keyword(s):  
B Lymphocytes ◽  
Adhesion Molecule ◽  
Human Lymphocytes ◽  
Normal Subjects ◽  
Cell Types ◽  
Surface Expression ◽  
Lymphocytic Leukemia ◽  
Functional Responses ◽  
Intracellular Expression ◽  
Selective Channel

Lymphocytes from normal subjects and patients with B-chronic lymphocytic leukemia (B-CLL) show functional responses to extracellular ATP characteristic of the P2X7receptor (previously termed P2Z). These responses include opening of a cation-selective channel/pore that allows entry of the fluorescent dye ethidium and activation of a membrane metalloprotease that sheds the adhesion molecule L-selectin. The surface expression of P2X7receptors was measured in normal leucocytes, platelets, and B-CLL lymphocytes and correlated with their functional responses. Monocytes showed four- to fivefold greater expression of P2X7than B, T, and NK lymphocytes, whereas P2X7expression on neutrophils and platelets was weak. All cell types demonstrated abundant intracellular expression of this receptor. All 12 subjects with B-CLL expressed lymphocyte P2X7at about the same level as B lymphocytes from normal subjects. P2X7function, measured by ATP-induced uptake of ethidium, correlated closely with surface expression of this receptor in normal and B-CLL lymphocytes and monocytes ( n = 47, r = 0.70; P< 0.0001). However, in three patients the ATP-induced uptake of ethidium into the malignant B lymphocytes was low or absent. The lack of P2X7function in these B lymphocytes was confirmed by the failure of ATP to induce Ba2+uptake into their lymphocytes. This lack of function of the P2X7receptor resulted in a failure of ATP-induced shedding of L-selectin, an adhesion molecule that directs the recirculation of lymphocytes from blood into the lymph node.

Morphilogy and Ultrastructure of in Vitro Cultures of Aortic Endothelial Cells Interacting with Antibodies

1979 ◽  
Author(s):  
S. Korach ◽  
D. Ngo
Keyword(s):  
Endothelial Cells ◽  
Cell Surface ◽  
Vascular Endothelial Cells ◽  
Intercellular Junctions ◽  
Cell Types ◽  
Endothelial Damage ◽  
Antibody Concentration ◽  
High Yields ◽  
Scanning Em

Adult pig aortas, sectioned longitudinally, were incubated in 0.1% collagenase-PBS (15 mn, 37°C). Gentle scraping of the lumenal surface resulted in high yields (3-4 x 106 cell/aorta) of viable endothelial cells, essentially devoid of other cell types by morphological and immunochemical (F VIII-antigen) criteria. Confluent monolayers were incubated for various times (5 mn to 1 wk) with decomplemented rabbit antisera raised against pig endothelial cells. Changes in cell morphology appeared to depend on antibody concentration rather than on duration of contact with antiserum. High concentrations of antiserum (5 to 20%) led to cytoplasmic shredding, bulging of cells and extensive vacuolization, whereas at lower concentrations, cells appeared almost normal. Transmission EM studies by the indirect immunoperoxydase method showed antibodies reacting with unfixed cells to be distributed all over the upper cell surface, in the outer parts of intercellular junctions, and within numerous pinocytotic vesicles. Much weaker reactions could also be seen at the lower cell surface. When viewed under the Scanning EM, antiserum-treated endothelial cells also disclosed antibody concentration-dependent bulging and release of cells from their substrate. In vitro studies of gradual modifications of vascular endothelial cells acted upon by antibodies should provide a better understanding of the structural and biochemical processes underlying endothelial damage and detachment.

scholarly journals Proteus mirabilis Urease: Unsuspected Non-Enzymatic Properties Relevant to Pathogenicity

2021 ◽  
Vol 22 (13) ◽  
pp. 7205
Author(s):  
Matheus V. C. Grahl ◽  
Augusto F. Uberti ◽  
Valquiria Broll ◽  
Paula Bacaicoa-Caruso ◽  
Evelin F. Meirelles ◽  
...  
Keyword(s):  
Proteus Mirabilis ◽  
Stone Formation ◽  
Cell Types ◽  
Bioinformatic Analysis ◽  
Urinary Stone ◽  
Enzymatic Properties ◽  
Hek293 Cells ◽  
Urinary Stones ◽  
Isolated Cells ◽  
Tnf Α

Infection by Proteus mirabilis causes urinary stones and catheter incrustation due to ammonia formed by urease (PMU), one of its virulence factors. Non-enzymatic properties, such as pro-inflammatory and neurotoxic activities, were previously reported for distinct ureases, including that of the gastric pathogen Helicobacter pylori. Here, PMU was assayed on isolated cells to evaluate its non-enzymatic properties. Purified PMU (nanomolar range) was tested in human (platelets, HEK293 and SH-SY5Y) cells, and in murine microglia (BV-2). PMU promoted platelet aggregation. It did not affect cellular viability and no ammonia was detected in the cultures’ supernatants. PMU-treated HEK293 cells acquired a pro-inflammatory phenotype, producing reactive oxygen species (ROS) and cytokines IL-1β and TNF-α. SH-SY5Y cells stimulated with PMU showed high levels of intracellular Ca2+ and ROS production, but unlike BV-2 cells, SH-SY5Y did not synthesize TNF-α and IL-1β. Texas Red-labeled PMU was found in the cytoplasm and in the nucleus of all cell types. Bioinformatic analysis revealed two bipartite nuclear localization sequences in PMU. We have shown that PMU, besides urinary stone formation, can potentially contribute in other ways to pathogenesis. Our data suggest that PMU triggers pro-inflammatory effects and may affect cells beyond the renal system, indicating a possible role in extra-urinary diseases.

scholarly journals Half-life modeling of basic fibroblast growth factor released from growth factor-eluting polyelectrolyte multilayers

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ivan Ding ◽  
Amy M. Peterson
Keyword(s):  
Cell Culture ◽  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Basic Fibroblast Growth Factor ◽  
Half Life ◽  
Cell Types ◽  
Polyelectrolyte Multilayers ◽  
Enzyme Linked Immunosorbent Assay ◽  
Fibroblast Growth ◽  
Cell Culture Study

AbstractGrowth factor-eluting polymer systems have been widely reported to improve cell and tissue outcomes; however, measurements of actual growth factor concentration in cell culture conditions are limited. The problem is compounded by a lack of knowledge of growth factor half-lives, which impedes efforts to determine real-time growth factor concentrations. In this work, the half-life of basic fibroblast growth factor (FGF2) was determined using enzyme linked immunosorbent assay (ELISA). FGF2 release from polyelectrolyte multilayers (PEMs) was measured and the data was fit to a simple degradation model, allowing for the determination of FGF2 concentrations between 2 and 4 days of culture time. After the first hour, the FGF2 concentration for PEMs assembled at pH = 4 ranged from 2.67 ng/mL to 5.76 ng/mL, while for PEMs assembled at pH = 5, the concentration ranged from 0.62 ng/mL to 2.12 ng/mL. CRL-2352 fibroblasts were cultured on PEMs assembled at pH = 4 and pH = 5. After 2 days, the FGF2-eluting PEM conditions showed improved cell count and spreading. After 4 days, only the pH = 4 assembly condition had higher cells counts, while the PEM assembled at pH = 5 and PEM with no FGF2 showed increased spreading. Overall, the half-life model and cell culture study provide optimal concentration ranges for fibroblast proliferation and a framework for understanding how temporal FGF2 concentration may affect other cell types.

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