Abstract-We studied the association between the production of reactive oxygen species, actin organization, and cellular motility. We have used an endothelial cell monolayer-wounding assay to demonstrate that the cells at the margin of the wound thus created produced significantly more free radicals than did cells in distant rows. The rate of incorporation of actin monomers into filaments was fastest at the wound margin, where heightened production of free radicals was detected. We have tested the effect of decreasing reactive oxygen species production on the migration of endothelial cells and on actin polymerization. The NADPH inhibitor diphenylene iodonium and the superoxide dismutase mimetic manganese (III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP) virtually abolished cytochalasin D-inhibitable actin monomer incorporation at the fast-growing barbed ends of filaments. Moreover, endothelial cell migration within the wound was significantly retarded in the presence of both diphenylene iodonium and MnTMPyP. We conclude that migration of endothelial cells in response to loss of confluence includes the intracellular production of reactive oxygen species, which contribute to the actin cytoskeleton reorganization required for the migratory behavior of endothelial cells. (Circ Res. 2000;86:549-557.)

Despite its small size, profilin is an amazingly diverse and sophisticated protein whose precise role in cells continues to elude the understanding of researchers 15 years after its discovery. Its ubiquity, abundance and necessity for life in more evolved organisms certainly speaks for its extreme importance in cell function. So far, three ligands for profilin have been well-characterized in vitro: actin monomers, membrane polyphosphoinositides and poly-L-proline. In the years following its discovery, profilin's role in vivo progressed from that of a simple actin-binding protein which inhibits actin polymerization, to one which, as an important regulator of the cytoskeleton, can even promote actin polymerization under the appropriate circumstances. In addition, interactions with components of the phosphatidylinositol cycle and the RAS pathway in yeast implicate profilin as an important link through which the actin cytoskeleton is able to communicate with major signaling pathways.