Induction of LFA‐1‐Dependent Neutrophil Rolling on ICAM‐1 by Engagement of E‐Selectin

Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
Microcirculation (Impact Factor: 2.26). 04/2006; 13(2):99-109. DOI: 10.1080/10739680500466376
Source: PubMed

ABSTRACT To study rolling of mouse neutrophils on E-selectin and ICAM-1 in an ex vivo flow chamber system.
The authors developed a small autoperfused flow chamber (20 x 200-microm cross section) that allows direct visualization of cells with and without fluorescent labeling and does not require recirculation of blood.
Neutrophils rolled on E-selectin alone, but were unable to interact with immobilized ICAM-1. When ICAM-1 was co-immobilized with E-selectin, the number of cells that rolled was doubled, but no significant firm adhesion was observed. This phenomenon was specific for E-selectin, and no enhancement of rolling was observed when P-selectin was immobilized with ICAM-1. The increased neutrophil rolling seen on E-selectin and ICAM-1 substrates required beta2 integrins. Treating mice with antibodies to the beta2 integrins LFA-1 and Mac-1 showed that LFA-1 was primarily responsible for mediating rolling on ICAM-1 in this model. Increased rolling on E-selectin and ICAM-1 was significantly reduced following administration of a specific p38 mitogen-activated protein kinase (MAPK) inhibitor.
The data show that neutrophil rolling on E-selectin leads to partial activation of LFA-1, enabling LFA-1-dependent rolling on ICAM-1. This mechanism is likely to amplify and accelerate neutrophil recruitment in inflammation.

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    • "While signaling events that follow the ligation of selectins by PSGL-1 are already described [26] [40], it is noteworthy to mention that for full integrin activation in leukocytes, additional stimuli such as other selectins, cytokines and chemokines are also required (Fig. 1). In their absence, P-selectin binding can only prime the neutrophil integrin, a process which is not sufficient for the full arrest of the cell [40] [41] [42]. These observations suggest that P-selectin stimulation acts synergistically with proinflammatory stimuli such as cytokines, chemokines and chemoattractants to induce full integrin activation [40]. "
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    • "Extended β2 integrin conformations with high topographical availability of the ligand-binding headpiece but low affinity for the ligand have been also postulated (Salas et al., 2002, 2006). This extended but low/intermediateaffinity conformation may increase the capability of LFA-1 to mediate rolling on ICAM-1 upon selectin triggering (Chesnutt et al., 2006; Zarbock et al., 2007; Miner et al., 2008). It is important to emphasize that low-, intermediate-, and high-affinity integrins likely represent discrete, reversible, states in a continuum of integrin conformational changes (Figure 1). "
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    • "Blood-Perfused Microflow Chamber In order to investigate the rolling velocity, the number of rolling cells, and adherent cells, we used a recently described microflow chamber system (Chesnutt et al., 2006; Smith et al., 2006). 20 3 200 mm rectangular glass capillaries were filled with E-selectin (30 mg/ml) or P-selectin (20 mg/ml) alone or in combination with ICAM-1 (15 mg/ml) and/or CXCL1 (10 mg/ml) for 2 hr and blocked for 1 hr with 10% casein (Pierce Chemicals, Dallas, TX). "
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