Role of phosphatidylinositol 3-kinase-gamma in mediating lung neutrophil sequestration and vascular injury induced by E. coli sepsis. 
We addressed the in vivo role of phosphatidylinositol 3-kinase-gamma (PI3K-gamma) in signaling the sequestration of polymorphonuclear leukocytes (PMNs) in lungs and in the mechanism of inflammatory lung vascular injury.  We studied mice with deletion of the p110 catalytic subunit of PI3K-gamma (PI3K-gamma(-/-) mice).  We measured lung tissue PMN sequestration, microvascular permeability, and edema formation after bacteremia induced by intraperitoneal Escherichia coli challenge.  PMN infiltration into the lung interstitium in PI3K-gamma(-/-) mice as assessed morphometrically was increased 100% over that in control mice within 1 h after bacterial challenge.  PI3K-gamma(-/-) mice also developed a greater increase in lung microvascular permeability after E. coli challenge, resulting in edema formation.  The augmented lung tissue PMN sequestration in PI3K-gamma(-/-) mice was associated with increased expression of the PMN adhesive proteins CD47 and beta(3)-integrins.  We observed increased association of CD47 and beta(3)-integrins with the extracellular matrix protein vitronectin in lungs of PI3K-gamma(-/-) mice after E. coli challenge.  PMNs from these mice also showed increased beta(3)-integrin expression and augmented beta(3)-integrin-dependent PMN adhesion to vitronectin.  These results point to a key role of PMN PI3K-gamma in negatively regulating CD47 and beta(3)-integrin expression in gram-negative sepsis.  PI3K-gamma activation in PMNs induced by E. coli may modulate the extent of lung tissue PMN sequestration secondary to CD47 and beta(3)-integrin expression.  Therefore, the level of PI3K-gamma activation may be an important determinant of PMN-dependent lung vascular injury.