Role of glycocalyx in leukocyte-endothelial cell adhesion

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.