Regulation of Hyperoxia-induced NADPH Oxidase Activation in Human Lung Endothelial Cells by the Actin Cytoskeleton and Cortactin

Abstract

Although the actin cytoskeleton has been implicated in the control of NADPH oxidase in phagocytosis, very little is known about the cytoskeletal regulation of endothelial NADPH oxidase assembly and activation. Here, we report a role for cortactin and the tyrosine phosphorylation of cortactin in hyperoxiainduced NADPH oxidase activation and ROS production in human pulmonary artery ECs (HPAECs). Exposure of HPAECs to hyperoxia for 3 h induced NADPH oxidase activation, as demonstrated by enhanced superoxide production. Hyperoxia also caused a thickening of the subcortical dense peripheral F-actin band and increased the localization of cortactin in the cortical regions and lamellipodia at cell-cell borders that protruded under neighboring cells. Pretreatment of HPAECs with the actin-stabilizing agent phallacidin attenuated hyperoxia-induced cortical actin thickening and ROS production, whereas cytochalasin D and latrunculin A enhanced basal and hyperoxia-induced ROS formation. In HPAECs, a 3-h hyperoxic exposure enhanced the tyrosine phosphorylation of cortactin and interaction between cortactin and p47 phox , a subcomponent of the EC NADPH oxidase, when compared with normoxic cells. Furthermore, transfection of HPAECs with cortactin small interfering RNA or myristoylated cortactin Src homology domain 3 blocking peptide attenuated ROS production and the hyperoxia-induced translocation of p47 phox to the cell periphery. Similarly, down-regulation of Src with Src small interfering RNA attenuated the hyperoxia-mediated phosphorylation of cortactin tyrosines and blocked the association of cortactin with actin and p47phox . In addition, the hyperoxia-induced generation of ROS was significantly lower in ECs expressing a tyrosine-deficient mutant of cortactin than in vector control or wild-type cells. These data demonstrate a novel function for cortactin and actin in hyperoxiainduced activation of NADPH oxidase and ROS generation in human lung endothelial cells. production that is dependent on NADPH oxidase activation and independent of the mitochondrial electron transport or xanthine/xanthine oxidase systems (10). The mechanisms of NADPH oxidase activation are complex. In phagocytes, activation of NADPH oxidase requires serine phosphorylation of the cytosolic p47 phox , p67 phox , and p40 phox components, assembly of the phosphorylated subunits with Rac2, and translocation to the phagosomes for association with cytochrome b 558. Here, one-electron reduction of molecular O 2 to O 2 . occurs with NADPH as the electron donor (7). In leukocytes, formyl-Met-Leu-Phe-OH or phorbol ester stimulates phosphorylation of p47 phox at multiple serine residues through reactions involving several protein kinases such as protein kinase C, protein kinase A, and mitogen-activated protein kinases (14 -17). In HPAECs, tumor necrosis factor-␣-medi-*This work was supported by National Institutes of Health Grants RO1 HL 69909 (to V. N.), PO1 HL 58064 (to V. N. and J. G. N. G.) and DE13079-01 and AI061042 (to L. H. R.). The costs of publication...

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