Blockade of class IA phosphoinositide 3-kinase in neutrophils prevents NADPH oxidase activation- and adhesion-dependent inflammation

We examined the role of class IA phosphoinositide 3-kinase (PI3K) in the regulation of activation of NADPH oxidase in PMNs and the mechanism of PMN-dependent lung inflammation and microvessel injury induced by the pro-inflammatory cytokine TNF-α. TNF-α stimulation of PMNs resulted in superoxide production that was dependent on CD11b/CD18-mediated PMN adhesion. Additionally, TNF-α induced the association of CD11b/CD18 with the NADPH oxidase subunit Nox2 (gp91^phox) and phosphorylation of p47 ^phox, indicating the CD11b/CD18 dependence of NADPH oxidase activation. Transduction of wild-type PMNs with Δp85 protein, a dominant-negative form of the class IA PI3K regulatory subunit, p85α, fused to HIV-TAT (TAT-Δp85) prevented (i) CD11b/CD18-dependent PMN adhesion, (ii) interaction of CD11b/CD18 with Nox2 and phosphorylation of p47^phox, and (iii) PMN oxidant production. Furthermore, studies in mice showed that i.v. infusion of TAT-Δp85 significantly reduced the recruitment of PMNs in lungs and increase in lung microvascular permeability induced by TNF-α. We conclude that class IA PI3K serves as a nodal point regulating CD11b/CD18-integrin-dependent PMN adhesion and activation of NADPH oxidase, and leads to oxidant production at sites of PMN adhesion, and the resultant lung microvascular injury in mice.