Macrophage activation with phorbol myristate acetate is associated with cellular lipid peroxidation

The present study analyzed the association between two major processes that occur during atherogenesis: macrophage activation and peroxidation of the cellular lipids. Macrophage activation was achieved by cell incubation with phorbol myristate acetate (PMA) for 24 h at 37 degrees C, and was determined as: a) PMA concentration-dependent increment in the release of beta-glucuronidase, b) decrement in the procoagulant activity, and c) increment in the release of superoxides from the cells. PMA-induced macrophage activation was accompanied by cellular lipid peroxidation, as measured by increased formation of lipid peroxides (by 435%), thiobarbituric acid-reactive substances (TBARS) (by 26%), and conjugated dienes (by 77%) in comparison with control nonactivated cells. The maximal effect of PMA on lipid peroxidation in macrophages was achieved within 1 h of cell incubation with PMA. This effect was demonstrated in J-774 A.1 macrophages, as well as in mouse peritoneal, macrophages, U-937 and P-338 macrophage cell lines. Upon incubation of macrophages with 4 alpha phorbol 12, 13 didecanoate, an analogue of PMA (which, unlike PMA, does not activate protein kinase C), macrophage lipid peroxidation was lower compared with PMA, suggesting a role for protein kinase C in cellular lipid peroxidation. Analysis of cellular antioxidants under PMA-induced macrophage activation revealed a decrease of 50% in total glutathione, and in catalase levels following treatment with 100 nM PMA compared with control cells. In summary, our study demonstrates that PMA-activated macrophages undergo significant lipid peroxidation, which is associated with reduced activity of the cellular antioxidative system.