Protein Kinase C-ζ Mediates Lung Injury Induced by Diesel Exhaust Particles

Recently, we reported that diesel exhaust particles (DEPs) disrupt tight junctions (TJs) in alveolar epithelial cells (AECs) via an increase in reactive oxygen species (ROS). In this study, we investigated the role of protein kinase C (PKC)-zeta activation in DEP-induced lung injury. C57/bl6 mice were instilled intratracheally with 50 mu l of saline containing 100 mu g of DEPs or titanium dioxide (TiO2). Twenty-four hours later, bronchoalveolar lavage was performed to assess neutrophil counts and protein concentrations. In addition, in vitro experiments were performed in primary rat and human AECs exposed to DEPs (50 mu g/cm(2)) for 3 hours. Transepithelial electrical conductance was measured, and TJ protein association was analyzed by immuno-precipitation. To determine whether the overexpression of antioxidants prevented DEP-induced lung injury, AECs and mice were infected with adenoviruses containing catalase and manganese superoxide dismutase (MnSOD) plasmids. In vivo, the overexpression of catalase and MnSOD prevented DEP-induced neutrophil recruitment. The inhibition of PKC-zeta activation also prevented DEP-induced neutrophil recruitment in vivo. In vitro, DEPs activated PKC-zeta in AECs, but not in alveolar macrophages. Using a specific myristolated PKC-zeta pseudosubstrate pepetide (PKC-zeta ps), we showed that PKC-zeta mediated the DEP-induced dissociation of occludinand zonula occludin-1 (ZO1) in rat and human AECs. In addition, the overexpression of constitutively active PKC-zeta induced the dissociation of occludin and ZO1 in AECs. DEP-induced TJ disruption occurs via PKC-zeta. TJ disruption seems to be in part responsible for DEP-induced lung injury.