Oxidant and angiotensin II-induced subcellular translocation of protein kinase C in pulmonary artery endothelial cells.

Abstract

We recently reported that nitrogen dioxide (NO2), an environmental oxidant, alters the dynamics of the plasma membrane lipid bilayer structure, resulting in increased phosphatidylserine content and angiotensin II (Ang II) receptor binding. Angiotensin II is known to elicit receptor-mediated stimulation of diacylglycerol (DAG) production in pulmonary artery endothelial cells. Because protein kinase C (PKC) is a phosphatidylserine-dependent enzyme and is activated by DAG, we examined whether NO2 resulted in activation and/or translocation of PKC from predominantly cytosolic to membrane fractions of these cells. We also evaluated whether NO2 exposure resulted in increased production of DAG in pulmonary artery endothelial cells. Exposure to 5 ppm NO2 for 1-24 hr resulted in significant increases in PKC activity in the cytosolic and membrane fractions (p less than 0.05 for both fractions) compared to activities in control fractions. Exposure to Ang II resulted in translocation of PKC activity from cytosol to membrane fractions of both control and NO2-exposed cells. This translocation of PKC from cytosolic to membrane fraction was prevented by the specific receptor antagonist [Sar1 Ile8] Ang II. Exposure of 5 ppm NO2 for 1-24 hr provoked rapid increases in [3H]glycerol labeling of DAG in pulmonary artery endothelial cells. These results demonstrate that exposure to NO2 increases the production of second messenger DAG and activates PKC in both the cytosolic and membrane fractions, whereas Ang II stimulates the redistribution of PKC from cytosolic to membrane fractions of pulmonary artery endothelial cells.