G protein-coupled receptor ca 21-linked mlitochondrial reactive oxygen species are essential for endothelial/leukocyte adherencevt

Receptor-mediated signaling is commonly associated with multiple functions, including the production of reactive oxygen species. However, whether mitochondrion-derived superoxide (mROS) contributes directly to physiological signaling is controversial. Here we demonstrate a previously unknown mechanism in which physiologic Ca2+-evoked mROS production plays a pivotal role in endothelial cell (EC) activation and leukocyte firm adhesion. G protein-coupled receptor (GPCR) and tyrosine kinase-mediated inositol 1,4,5 trisphosphate-dependent mitochondrial Ca2+ uptake resulted in NADPH oxidase-independent mROS production. However, GPCR-linked mROS production did not alter mitochondrial function or trigger cell death but rather contributed to activation of NF-kappa B and leukocyte adhesion via the EC induction of intercellular adhesion molecule 1. Dismutation of mROS by manganese superoxide dismutase overexpression and a cellpermeative superoxide dismutase mimetic ablated NF-kappa B transcriptional activity and facilitated leukocyte detachment from the endothelium under simulated circulation following (PCR- but not cytokine-induced activation. These results demonstrate that mROS is the downstream effector molecule that translates receptormediated Ca2+ signals into proinflammatory signaling and leukocyte/EC firm adhesion.