Selectin-mediated rolling of neutrophils on immobilized platelets

Abstract

Interaction between neutrophils and platelets at the site of vascular damage or in ischaemic tissue may promote thrombosis and/or vascular occlusion. To study this interaction, we have developed a novel technique that allows visualization of adhesion of flowing neutrophils to immobilized, activated platelets. The total number of adherent neutrophils decreased with increasing wall shear stress in the range 0.05 to 0.4 Pa. Although a proportion of the adherent neutrophils were stationary, most were rolling with a velocity greater than 0.4 micron/s. The percentage of rolling cells increased with increasing wall shear stress, but the mean rolling cell velocity was nearly independent of shear stress. Adhesion of neutrophils was nearly abolished by treatment of the platelets with antibody to P-selectin, or by treatment of neutrophils with either neuraminidase, dextran sulfate, or EDTA. Studies with a series of antibodies to L-selectin (TQ-1, Dreg- 56, LAM1–3, and LAM1–10) suggested that this molecule was one neutrophil ligand for rolling adhesion. Thus, sialylated carbohydrate on neutrophils appears essential for P-selectin-mediated adhesion, and a proportion of this ligand may be presented by L-selectin. Treatment of the neutrophils with N-formyl-methionyl-leucyl-phenylalanine decreased the number of rolling cells, and increased the rolling velocity, possibly due to shedding of neutrophil ligand(s) and/or cell shape change. In vivo, immobilized platelets could play an important role in promoting attachment of neutrophils to vessel walls, eg, by slowing neutrophils so that integrin-mediated immobilization could occur.

The polysaccharide fucoidan inhibits microvascular thrombus formation independently from P‐ and l‐selectin function in vivo

“…The selectins have been implicated in thrombogenesis by supporting platelet±platelet and platelet±leukocyte aggregation, in addition to mediate low-af®nity binding of platelets and leukocytes to endothelial cells known as cell rolling [2,8,24,25]. In light of the fact that fucoidan interferes with the activity of P-and L-selectin [14,15], we wanted to de®ne the potential contribution of these selectins in the process of thrombus induction.…”

The role of P‐selectin in the immune destruction of platelets

“…The primary role of platelets is the maintenance of haemostasis by thrombus formation at sites of vascular damage. P-selectin is expressed at increased levels on activated platelets and, by binding to P-selectin glycoprotein ligand 1 (PSGL-1), P-selectin has been reported to mediate the slowing of leucocytes for firm adhesion at the sites of such damage (Jungi et al, 1986;Buttrum et al, 1993). Platelets have also been found to bind to monocytes in a P-selectin-dependent manner in whole blood (Rinder et al, 1991a,b;de Bruijne-Admiraal et al, 1992).…”

CD45 Engagement Induces L‐Selectin Down‐Regulation

“…Peripheral blood mononuclear cell aggregation is rapidly induced by PKC activation or by distinct anti-CD45 MoAbs; blocking PKC activity inhibits phorbol ester-mediated cluster formation but accelerates that induced by anti-CD45 [10]. Sequential L-selectin down-regulation and 2 (CD18) integrin up-regulation is a hallmark of the response of granulocytes to chemotactic factors [17,26]. Granulocyte CD11b/CD18 up-regulation can be induced in much the same way as L-selectin down-regulation by inhibition of PTPase, PKC activation or PKC inhibition [47].…”

“…Selectins are a family of adhesion molecules with a distinct Nterminal C-type lectin domain binding to acidic carbohydrate structures in a Ca 2+ -dependent fashion. L-selectin (CD62L) which is present on the outer plasma membrane of microvillar projections of leucocytes [14] initiates the reversible attachment of flowing leucocytes to endothelial cells [15], endotheliumbound leucocytes [16] and immobilized platelets [17], thereby directing neutrophils into areas of acute inflammation [18], and lymphocytes into sites of chronic inflammation and secondary lymphoid organs. The intracellular domain of L-selectin does not appear to be endowed with enzymatic activity but is required for L-selectin-mediated attachment by anchoring the molecule to the cytoskeleton [19] while its role in outside-in signalling is less clear [20,21].…”