C Leculier1, O Benzerara, N Couprie
1Laboratoire de Biochimie B, Hôpital Edouard Herriot, Lyon, France.
This study explores how heparin interacts with human neutrophils. Researchers found that heparin binds to these immune cells in a specific and reversible way. They identified a 130 kD protein on the cell surface that mediates this interaction. The binding does not affect heparin's anticoagulant activity or thrombin inactivation by antithrombin III. The study suggests that heparin may influence neutrophil function through this binding protein. The findings could help explain how heparin affects immune responses in clinical settings.
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Area of Science:
Background:
Prior research has shown that heparin interacts with various cell types, but the nature of its binding to neutrophils remained unclear. It was already known that heparin can modulate immune cell behavior, yet the specific mechanisms on polymorphonuclear leucocytes had not been fully resolved. That uncertainty drove this investigation into whether heparin binding is specific and how it affects neutrophil function. No prior work had resolved the molecular weight of the binding protein involved. This gap motivated the current study to characterize the binding properties and identify the associated protein. The functional consequences of this interaction were also unknown. This paper addresses the need for a detailed analysis of heparin-neutrophil interactions. Understanding these interactions could clarify how heparin influences immune responses in clinical settings.
Purpose Of The Study:
The aim of this study was to determine whether human neutrophils bind heparin in a specific and saturable manner. The researchers sought to identify the binding characteristics and the associated protein. They wanted to assess if this binding affects heparin's anticoagulant activity. The study also aimed to investigate whether the binding protein influences thrombin inactivation by antithrombin III. A key question was whether the binding is reversible and how it is affected by chelating agents. The researchers also wanted to determine the molecular weight of the binding protein. This work aimed to clarify the functional implications of heparin binding on neutrophil surfaces. The findings could help explain how heparin modifies neutrophil function in vivo.
The study found that heparin binds to neutrophils via a specific 130 kD cell surface protein.
Radio-iodinated cell lysates were used in heparin affinity chromatography followed by SDS-PAGE to identify the 130 kD protein.
Disodium ethylenediamine tetraacetic acid was used to test if calcium is necessary for heparin binding to neutrophils.
Cell surface-bound heparin does not interfere with thrombin inactivation by antithrombin III.
Main Methods:
The study used heparin binding assays to measure interaction with neutrophils. Radio-iodinated cell lysates were used in affinity chromatography to isolate binding proteins. Polyacrylamide gel electrophoresis was performed with sodium dodecylsulphate to determine protein molecular weight. The dissociation constant was calculated from binding data. Disodium ethylenediamine tetraacetic acid was used to test binding inhibition. Cell surface binding was analyzed for functional activity. Thrombin inactivation by antithrombin III was assessed in the presence of bound heparin. The binding data were compared with anticoagulant activity measurements to assess independence.
Main Results:
Heparin binding to neutrophils was found to be specific, rapid, and saturable. A single class of binding sites was identified with a dissociation constant of 1.22 mumol/l. Each neutrophil had approximately 7.7 x 10(6) binding sites. The binding was reversible and not dependent on heparin's anticoagulant activity. A 130 kD protein was identified as the heparin-binding component. Disodium ethylenediamine tetraacetic acid inhibited the binding process. Cell surface-bound heparin did not interfere with thrombin inactivation. These findings suggest that the binding is mediated by a specific cell surface protein.
Conclusions:
The authors conclude that heparin interacts with neutrophils through a specific cell-surface binding protein. This interaction is independent of heparin's anticoagulant effects. The binding protein has a molecular weight of 130 kD. The binding is reversible and saturable, indicating a defined receptor mechanism. Disodium ethylenediamine tetraacetic acid inhibits this binding, suggesting a calcium-dependent process. Cell surface-bound heparin does not affect thrombin inactivation by antithrombin III. These findings suggest that the binding may influence neutrophil function in the presence of heparin. The study provides evidence for a direct interaction between heparin and neutrophil surface proteins.
The dissociation constant was measured at 1.22 mumol/l.
The study suggests that heparin interacts with a specific cell surface protein on neutrophils.