Phosphatidylinositol 3-Kinase γ Signaling through Protein Kinase Cζ Induces NADPH Oxidase-mediated Oxidant Generation and N F-κB Activation in Endothelial Cells.

We addressed the role of class 1B phosphatidylinositol 3-kinase (PI3K) isoform PI3Kγ in mediating NADPH oxidase activation and reactive oxidant species (ROS) generation in endothelial cells (ECs) and of PI3Kγ-mediated oxidant signaling in the mechanism of NF-κB activation and intercellular adhesion molecule (ICAM)-1 expression. We used lung microvascular ECs isolated from mice with targeted deletion of the p110γ catalytic subunit of PI3Kγ. Tumor necrosis factor (TNF) α challenge of wild type ECs caused p110γ translocation to the plasma membrane and phosphatidylinositol 1,4,5-trisphosphate production coupled to ROS production; however, this response was blocked in p110γ-/- ECs. ROS production was the result of TNFα activation of Ser phosphorylation of NADPH oxidase subunit p47phox and its translocation to EC membranes. NADPH oxidase activation failed to occur in p110γ-/- ECs. Additionally, the TNFα-activated NF-κB binding to the ICAM-1 promoter, ICAM-1 protein expression, and PMN adhesion to ECs required functional P13Kγ. TNFα challenge of p110γ-/- ECs failed to induce phosphorylation of PDK1 and activation of the atypical PKC isoform, PKCζ. Thus, PI3Kγ lies upstream of PKCζ in the endothelium,anditsactivationiscrucialinsignalingNADPHoxidase- dependent oxidant production and subsequent NF-κB activation and ICAM-1 expression. [ABSTRACT FROM AUTHOR]