Albumin inhibits neutrophil spreading and hydrogen peroxide release by blocking the shedding of CD43 (sialophorin, leukosialin)

Abstract

Abstract. Spreading of neutrophils on protein-coated surfaces is a pivotal event in their ability to respond to soluble, physiologic agonists by releasing large amounts of hydrolases and oxidants. Using neutrophils plated on serum-, fibrinogen-or fibronectin-coated surfaces, we investigated the effect of human serum albumin (HSA) on spreading-dependent neutrophil responses. HSA suppressed the respiratory burst of neutrophils in response to tumor necrosis factor-or (TNF), complement component C5a or formylated peptide, but not phorbol myristate acetate. HSA was suppressive only if added before the onset of the respiratory burst, and suppression was reversed when HSA was removed. Likewise, HSA selectively and reversibly inhibited TNF-induced cell spreading and the associated fall in cAMP. However, HSA did not hinder TNFinduced cell adherence to the same protein-coated surfaces.We investigated cell surface sialoproteins as modulators of cell spreading and as targets for the antispreading action of HSA. Oxidation of the cell surface with periodate followed by reduction with 3H-borohydride and immunoblotting with specific mAbs helped identify the predominant sialoprotein on human neutrophils as CD43 (sialophorin, leukosialin). Treatment of neutrophils with C perfringens sialidase desialylated CD43, markedly enhanced the ability of the cells to respond to TNF by spreading and undergoing a respiratory burst, and antagonized the ability of HSA to inhibit these responses. TNF-treated, adherent neutrophils shed CIM3, and this was blocked by HSA, but not by ovalbumin. Exogenous neutrophil elastase removed CD43 from the neutrophil surface. HSA blocked the actions of both sialidase and elastase on CD43. In contrast, ovalbumin did not block the action of sialidase on CD43, and HSA did not inhibit the ability of sialidase to hydrolyze a synthetic substrate. These results suggested that HSA might bind CD43. In fact, the extracellular portion of CD43 bound to HSA-Sepharose, but not to ovalbumin-or glycylglycine-Sepharose. Finally, two mAbs recognizing different epitopes on CD43 mimicked HSgs inhibitory effects on neutrophil function.Thus, HSA can dissociate attachment of neutrophils from spreading. This dissociation may help neutrophils migrate along a chemotactic gradient, while decreasing their release of oxidants. CIM3, a long, rigid molecule with a markedly negative charge, antagonizes neutrophil spreading. HSA appears to inhibit spreading-dependent neutrophil functions by binding to CD43 and interfering with the ability of neutrophils to shed it.T HE anti-infectious and pro-inflammatory functions of neutrophils are usually discharged after the cells have stopped circulating and have adhered to each other or to platelets, endothelium, parenchyma, stromal cells, or proteins of extracellular matrix. This has motivated a number of investigators to explore the biology of neutrophils adherent to model biological surfaces. A simple model consists of neutrophils plated on plastic or glass coated with plasma, serum, fibrinogen, fibr...

Metal-Protein Complex-Mediated Transport and Delivery of Ni2+ to TCR/MHC Contact Sites in Nickel-Specific Human T Cell Activation

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Recruitment of Murine Neutrophils in Vivothrough Endogenous Sialidase Activity

“…This may occur by removal of sialyl residues from specific, heavily sialylated molecules (e.g. leukosialin, also known as CD43) known to play a role in PMN adhesion to surfaces (40,41). Alternatively, the desialylation of multiple glycoconjugate species on both the PMN and/or adjacent endothelial cell surface may sufficiently decrease the net negative surface charge of either or both cell types with a reduction of repulsive forces.…”

The effect of starch-based biomaterials on leukocyte adhesion and activation in vitro

“…Proteins may however act in different ways. Some studies [34,36] demonstrated that some proteins enhance neutrophil activation, but other research showed that they can inhibit PMN resulting in a diminished inflammation [34,35]. The amount of protein pre-adsorbed on a surface can also affect cell adhesion by masking the surface properties of the underlying substrate and thus minimising the non-specific interactions [37].…”

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