Conjugated linoleic acid increases intracellular ROS synthesis and oxygenation of arachidonic acid in macrophages

Objective: Conjugated linoleic acids (CLAs) have potential anti atherosclerotic properties: they may inhibit atherosclerotic processes by reducing the intensity of inflammatory processes. However, in vivo studies have shown that the application of trans-10, cis-12 CLA in obese men increased their oxidative stress. The objective of this study was to determine whether CLA can lead to an increase in oxidative stress and to isoprostane synthesis in macrophages. Methods: Monocytes from peripheral blood and human monocytic leukemia cells were used in this study. Monocytes were differentiated to macrophages, and were incubated with 30 mu M cis-9, trans-11 CLA and trans-10, cis-12 CLA or linoleic acid for 2 jays. In some experiments the inhibitors of peroxisome proliferator-activated receptor-a (PPAR-a) or respiratory chain were added. After incubation, synthesis of reactive oxygen species (ROS), total cellular concentration of adenosine triphosphate, concentration of 8-epi-prostaglandin F-2 alpha, activity of cytoplasolic phospholipase A(2) (cPLA(2)), activity of mitochondria, and expression of mRNA of PPAR-a were measured. Results: In cells cultured with CLAs intercellular ROS synthesis increased. In this condition the mitochondrial energy potential was high, and the inhibitors of the respiratory chain and PPAR-a reduced ROS concentration. At the same time, the cPLA(2) activity was abolished. In contrast, 8-iPF(2)alpha III synthesis increased in CLA cells. Conclusion: Cultivation of cells with CLA leads to an increased ROS synthesis, partly by PPAR-a mechanism. An increase in ROS concentration and inhibition of cPLA(2) activity can stimulate oxygenation of arachidonic acid and contribute to an increase in 8-epi-PF2 alpha III level and in the apoptosis process in macrophages. (c) 2008 Elsevier Inc. All rights reserved.