Effects of Linoleic Acid Hydroperoxide on Phagocytotic Activity and on Microscopic Features of Macrophages Derived from Peripheral Monocytes

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The effects of linoleic acid hydroperoxide on macrophages derived from peripheral monocytes were investigated. The phagocytotic activity of macrophages was not inhibited in the presence of linoleic acid hydroperoxide up to 5nmol/ml (measured by the thiobarbituric acid reaction and expressed in terms of malondialdehyde), at which concentration cultured endothelial cells from the aorta are markedly injured. When we examined macrophages incubated with 5nmol/ml of the hydroperoxide by electron microscopy, however, the number of organelles was found to be increased and the electron density of the mitochondrial matrix was slightly decreased. As judged from the morphological changes, the susceptibility of macrophages to linoleic acid hydroperoxide seems to be in the same order as that of cultured smooth muscle cells from the aorta, but lower than that of cultured endothelial cells. In the presence of 15nmol/ml of the hydroperoxide, macrophages showed the features of marked degeneration, while still retained phagocytotic activity to a considerable extent. The significance of these phenomena in atherogenesis was discussed.