Hydrogen peroxide activation of endothelial cell-associated MMPs during VCAM-1-dependent leukocyte migration

Area of Science:

• Immunology
• Cell Biology
• Vascular Biology

Background:

• Leukocyte migration is essential for immune surveillance and inflammation.
• Site-specific migration depends on microenvironmental factors like adhesion molecules and chemokines.
• The role of endothelial cells in leukocyte extravasation is under investigation.

Purpose of the Study:

• To investigate the active role of endothelial cells in Vascular Cell Adhesion Molecule-1 (VCAM-1)-dependent leukocyte migration.
• To elucidate the molecular mechanisms involving endothelial NADPH oxidase and matrix metalloproteinases (MMPs).

Main Methods:

• Studied VCAM-1-dependent leukocyte migration.
• Investigated endothelial cell NADPH oxidase activation and reactive oxygen species (ROS) generation.
• Assessed endothelial cell-associated MMP activity using pharmacologic and antisense inhibition.
• Utilized antioxidants to scavenge ROS and inhibit MMPs.
• Administered bilirubin in vivo to block VCAM-1-dependent leukocyte migration in a mouse asthma model.

Main Results:

• VCAM-1 activates endothelial cell NADPH oxidase, generating hydrogen peroxide (H2O2).
• This ROS stimulates endothelial cell MMP activity within minutes, facilitating lymphocyte migration.
• Inhibition of NADPH oxidase or MMPs, or ROS scavenging, blocked VCAM-1-dependent migration.
• Antioxidants, including bilirubin in vivo, effectively inhibited VCAM-1-dependent leukocyte migration.

Conclusions:

• Endothelial cells play an active, rather than passive, role in VCAM-1-dependent leukocyte transendothelial migration.
• The VCAM-1/NADPH oxidase/ROS/MMP pathway is critical for leukocyte extravasation.
• Targeting this pathway with antioxidants may offer therapeutic strategies for inflammatory diseases like asthma.