Protein oxidation and proteolysis in RAW264.7 macrophages: effects of PMA activation

Macrophages are stimulable cells able to increase the production of reactiv e oxygen and nitrogen species dramatically for a short period of time. Free radicals and other oxidants are able to oxidize the intracellular protein pool. These oxidized proteins are selectively recognized and degraded by th e intracellular proteasomal system. We used the mouse macrophagelike cell l ine RAW264.7 to test whether macrophagial cells are able to increase their protein turnover after oxidative stress and whether this is accompanied by an increased protein oxidation. Macrophagial cells are particularly suscept ible to bolus additions of hydrogen peroxide and peroxynitrite. Tn further experiments we activated RAW264.7 cells with PMA to test whether the produc tion of endogenous oxidants has analogous effects. A clear dependence of th e protein turnover and protein oxidation on the oxidative burst could be me asured. In further experiments the role of the proteasomal system in the se lective removal of oxidized proteins could be revealed exploring the protea some specific inhibitor lactacystin. Therefore, although oxidants are able to attack the intracellular protein pool in macrophages, these cells are ab le to remove oxidized proteins selectively and protect the intracellular pr otein pool from oxidation. (C) 2001 Elsevier Science B.V. All rights reserv ed.