The internal redox balance of the cells influences the metabolism of lipids of dietary origin by J774 macrophages: Implications for foam cell formation

The effects of chylomicron remnants on lipid accumulation in J774 macrophag es, and the incorporation of radioactivity from remnant lipids radiolabelle d with [H-3]oleate into cellular lipids was investigated. After 24 h of inc ubation with chylomicron remnants, there was considerable accumulation of l ipid within the cells as assessed by staining with oil red O, indicating th at the particles induce the formation of foam cells. Fatty acids released f rom the radiolabelled remnant lipids after uptake were found to be incorpor ated into cellular triacylglycerol (52%), phospholipid (37%) and cholestery l ester (8%), but at higher remnant concentrations, the proportion used for triacylglycerol formation increased (up to 73%). When the macrophages were shifted into a pro-oxidising or pro-reducing state by incubation (24 h) wi th CuSO4 (2.5 muM) or N-acetylcysteine (5 mM), respectively, the incorporat ion of [H-3]oleate from remnant lipid into cellular triacylglycerol and pho spholipid was increased by 20-30% in the more oxidised as compared with the more reduced cells. These findings indicate that exposure of J774 macropha ges to chylomicron remnants leads to the accumulation of lipid within the c ells, and that this process is enhanced by pro-oxidising conditions. We con clude, therefore, that both lipids of dietary origin and the redox balance within macrophages may have a significant role in the induction of foam cel l formation. Copyright (C) 2001 S.Karger AG, Basel.