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Role of glycocalyx in leukocyte-endothelial cell adhesion
1Department of Bioengineering, Pennsylvania State University, University Park 16802, USA.
Abstract:
The binding of fluorescently labeled microspheres (FLMs, 0.1-microm diameter) coated with antibody (1a29) to ICAM-1 was studied in postcapillary venules during topical application of the chemoattractant N-formylmethionyl-leucyl-phenylalanine (fMLP). FLM adhesion to endothelial cells (ECs) increased dramatically from 50 to 150 spheres per 100-microm length of venule after superfusion of the mesentery with fMLP and equaled or exceeded levels of leukocyte (WBC) adhesion. Removal of the EC glycocalyx by micropipette infusion of the venule with heparinase increased FLM-EC adhesion to levels attained with fMLP. Subsequent application of fMLP did not increase FLM adhesion further, suggesting that the FLMs saturated all ICAM-1 binding sites. Perfusion with heparinase after suffusion with fMLP significantly increased FLM-EC adhesion above levels attained with fMLP. However, WBC adhesion fell because of possible removal of selectins necessary to maintain WBC rolling at the wall. It is concluded that the glycocalyx serves as a barrier to adhesion and that its shedding during natural activation of ECs may be an essential part of the inflammatory response.
Insights
The endothelial glycocalyx acts as a barrier to microsphere adhesion. Its shedding during inflammation is crucial for immune cell recruitment and the inflammatory response.
Area of Science:
- Immunology
- Cell Biology
- Biomedical Engineering
Background:
- Endothelial cells (ECs) play a key role in regulating immune cell trafficking.
- The endothelial glycocalyx, a layer on ECs, influences cell-cell interactions.
- Understanding the glycocalyx's role in inflammation is critical for developing new therapies.
Purpose of the Study:
- To investigate the role of the endothelial glycocalyx in regulating the adhesion of fluorescently labeled microspheres (FLMs) to ICAM-1.
- To determine how chemoattractants like N-formylmethionyl-leucyl-phenylalanine (fMLP) affect FLM and leukocyte (WBC) adhesion.
- To elucidate the contribution of the glycocalyx to the inflammatory response.
Main Methods:
- Utilized fluorescently labeled microspheres (FLMs) coated with antibody (1a29) to study binding to ICAM-1 on ECs in postcapillary venules.
- Applied topical chemoattractant N-formylmethionyl-leucyl-phenylalanine (fMLP) to superfuse the mesentery.
- Employed micropipette infusion of heparinase to remove the EC glycocalyx and assess its impact on FLM and WBC adhesion.
Main Results:
- FLM adhesion to ECs dramatically increased after fMLP superfusion, reaching levels comparable to WBC adhesion.
- Removal of the EC glycocalyx by heparinase significantly enhanced FLM adhesion.
- While heparinase treatment increased FLM adhesion, it decreased WBC adhesion, suggesting selectin removal.
Conclusions:
- The endothelial glycocalyx functions as a physical barrier, inhibiting microsphere and potentially leukocyte adhesion.
- Shedding of the glycocalyx during EC activation is a key event in initiating the inflammatory response.
- Modulating the glycocalyx could offer therapeutic strategies for inflammatory diseases.