α_Vβ₃ Integrin Regulation of Respiratory Burst in Fibrinogen Adherent Human Neutrophils

In response to inflammatory stimuli, microvascular endothelial cells become activated, initiating the capture and exit of neutrophils from the blood vessel and into the extravascular extracellular matrix (ECM). In the extravascular space, neutrophils bind to ECM proteins, regulating cellular functions via signaling through adhesion molecules known as integrins. The α_Vβ₃ integrin is an important mediator of neutrophil adhesion to ECM proteins containing the Arg-Gly-Asp (RGD) peptide sequence, including fibrinogen and fibronectin. Despite the abundance of RGD sequence in the ECM, adhesion molecule-mediated neutrophil activity has been focused on the β₂ (Mac-1, CD11b/CD18) and β₁ integrin response to matrix proteins. Here we investigated α_Vβ₃ integrin-mediated reactive oxidant suppression as a consequence of human neutrophil adhesion to RGD containing proteins. Using integrin ligand-modified (poly)ethylene glycol hydrogels and reactive oxygen species (ROS) sensitive fluorescent probes (dihydrotetramethylrhosamine, H₂TMRos), we evaluated integrin-peptide interactions that effectively regulate ROS generation. This study demonstrates that neutrophil adhesion suppresses ROS production in an α_Vβ₃-dependent manner. Additionally, we determine that p38 mitogen-activated protein kinase in the respiratory burst signaling pathway is interrupted by integrin-mediated adhesion. These data indicate that ECM/integrin interactions can induce α_Vβ₃-mediated adhesion dependent downstream signaling of ROS regulation via a Mac-1 independent mechanism.