Biorheology - Volume 52, issue 5-6

Authors: Paschall, Christopher D. | Klibanov, Alexander L. | Lawrence, Michael B.

Article Type: Research Article

Abstract: Background: During inflammation leukocyte attachment to the blood vessel wall is augmented by capture of near-wall flowing leukocytes by previously adherent leukocytes. Adhesive interactions between flowing and adherent leukocytes are mediated by L-selectin and P-selectin Glycoprotein Ligand-1 (PSGL-1) co-expressed on the leukocyte surface and ultimately regulated by hydrodynamic shear thresholding. Objective: We hypothesized that leukocyte deformability is a significant contributory factor in shear thresholding and secondary capture. Methods: Cytochalasin D (CD) was used to increase neutrophil deformability and fixation was used to reduce deformability. Neutrophil rolling on PSGL-1 coated planar surfaces and collisions with PSGL-1 coated …microbeads were analyzed using high-speed videomicroscopy (250 fps). Results: Increased deformability led to an increase in neutrophil rolling flux on PSGL-1 surfaces while fixation led to a decrease in rolling flux. Abrupt drops in flow below the shear threshold resulted in extended release times from the substrate for CD-treated neutrophils, suggesting increased bond number. In a cell-microbead collision assay lower flow rates were correlated with briefer adhesion lifetimes and smaller adhesive contact patches. Conclusions: Leukocyte deformation may control selectin bond number at the flow rates associated with hydrodynamic shear thresholding. Model analysis supported a requirement for both L-selectin catch-slip bond properties and multiple bond formation for shear thresholding. Show more

Keywords: Selectin, inflammation, PSGL-1, neutrophil, rolling, mechanokinetics

DOI: 10.3233/BIR-15064

Citation: Biorheology, vol. 52, no. 5-6, pp. 415-432, 2015

Authors: Lipowsky, Herbert H. | Lescanic, Anne | Sah, Rachna

Article Type: Research Article

Abstract: Background: The endothelial glycocalyx serves as a barrier to leukocyte (WBC)-endothelium (EC) adhesion. Shedding of glycans, by matrix metalloproteases (MMPs) exposes EC integrin receptors to facilitate firm adhesion. However, the effect of shedding on the strength of the adhesive bond remains to be determined. Objectives: Examine the effect of MMP inhibition on the kinetics of WBC-EC adhesion under normal and inflammatory conditions to delineate differences in the duration and number of adhesive bonds. Methods: WBC adhesion in post-capillary venules was observed in rat mesentery. Adhesion duration and off-rates (K OFF ) …were correlated with shear stress during adhesion in response to 1 µM fMLP or 0.5 µM doxycycline (doxy, to inhibit MMP activation). Results: Doxy increased mean adhesion time significantly from 2.5 (control) to 5.6 s, whereas fMLP increased it 8-fold to 20 s, which was not affected by pre-treatment with doxy. Estimates of the number of adhesive bonds (simplified Bell-model) revealed a significantly greater increase with fMLP compared to doxy alone, with no effect on fMLP by pretreatment with doxy. With doxy alone, K OFF was significantly 4-fold greater compared to fMLP, suggesting a much weaker bond. Conclusions: Although the increased number of bonds by MMP inhibition with doxy alone and fMLP were similar, the bonds due to doxy appeared weaker as evidenced by their shorter duration, and lesser reduction in K OFF relative to control. Thus doxy limits the availability of integrin binding sites during fMLP stimulated adhesion, but has a pro-adhesive effect due to increased ligands for WBC binding that arises from inhibition of normal sheddase activity on the EC. Show more

Keywords: Leukocyte adhesion, matrix metalloproteases, MMPs, adhesion duration, bond force

DOI: 10.3233/BIR-15063

Citation: Biorheology, vol. 52, no. 5-6, pp. 433-445, 2015

Authors: Morikis, Vasilios A. | Radecke, Chris | Jiang, Yanyan | Heinrich, Volkmar | Curry, Fitz-Roy | Simon, Scott I.

Article Type: Research Article

Abstract: Background: Recombinant atrial natriuretic peptide (ANP) is administered in patients with acute heart failure in Japan to improve renal function and hemodynamics, but its anti-inflammatory effect on activated leukocytes may also contribute to its therapeutic efficacy. Objective: Examine unconventional role of ANP in neutrophil adhesion to inflamed endothelium. Methods: Human neutrophils were perfused over endothelial monolayers in a microfluidic lab-chip assay. Cell rheology was assessed by micropipette aspiration to assess changes in cortical tension and viscosity. Fluorescence microscopy was applied to measure adhesive contact area and β 2 -integrin focal bond …formation. Results: ANP inhibited neutrophil rolling and firm adhesion without influencing the upregulation of cellular adhesion molecules on endothelium or the regulation of high affinity CD18 and shedding of L-selectin during neutrophil activation. Exposed to fluid shear, integrin mediated arrest was disrupted with ANP treatment, which elicited formation of long tethers and diminished cell spreading and contact. This correlated with a ∼40% increase in neutrophil viscosity and a reduction in the adhesive footprint. Conclusions: A decrease in cell deformation and neutrophil flattening with ANP results in fewer integrin bond clusters, which translates to higher tensile forces and impaired adhesion strengthening and cell detachment. Show more

Keywords: Atrial natriuretic peptide, neutrophil, adhesion, inflammation

DOI: 10.3233/BIR-15067

Citation: Biorheology, vol. 52, no. 5-6, pp. 447-463, 2015

Article Type: Other

Citation: Biorheology, vol. 52, no. 5-6, pp. 465-474, 2015