Role of pre-existing redox profile of human macrophages on lipid synthesis and cholesteryl ester cycle in presence of native, acetylated and oxidised low density lipoprotein.
The importance of the interactions of modified lipids and macrophages in foam cell generation is clear; however, little attention has been paid to the role of intra-macrophagic redox potential as a modulator of their lipid synthesis and metabolism. In this study, the effects of previously induced non-toxic manipulations of intracellular redox balance on lipid synthesis in human monocyte-derived macrophages (HMDM) was evaluated. Cells, pre-treated with 2.5 microM of the pro-oxidising agent CuSO(4) or with 5 mM of the antioxidant and thiol supplier N-acetylcysteine (NAC), were exposed to radiolabelled oleic acid alone or in combination with native low density lipoprotein (LDL) or modified LDL to evaluate the incorporation of radioactivity into cholesteryl ester, triacylglycerols and phospholipids. CuSO(4)-treated macrophages synthesised more lipids than NAC-treated cells in absence of exogenous lipid, and, generally, in the presence of native or acetylated, but oxidised LDL. In addition, the activities of the enzymes involved in cholesteryl ester storage were also influenced by the pro-oxidant condition. The ratio values between acyl-coenzyme A:cholesterol acyl transferase and cholesteryl ester hydrolase activity suggest that in CuSO(4)-treated macrophages the hydrolysis of cholesteryl ester is favoured with respect to esterification. The interaction of HMDM with oxidised LDL showed a significant different pattern in term of lipid synthesis with respect to those induced by native or acetylated LDL, disrespectful of the initial redox profile of the cells. On the whole, these results suggest that the pre-existing internal redox condition is a further parameter able to modulate the effects of native or acetylated LDL-cell interaction, influencing both HMDM lipid synthesis profile and cholesterol storage. Moreover, oxidised LDL represent a carrier of additional factor(s) able per se to introduce perturbation in the synthetic pathway of lipids, which is not influenced by the redox potential of the macrophage.
Bravo
E
E
Laboratory of Metabolism and Pathological Biochemistry, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy. bravo@iss.it
Napolitano
M
M
Rivabene
R
R
D000111:Acetylcysteine / Q000494:pharmacology; D002478:Cells, Cultured; D002788:Cholesterol Esters / Q000378:metabolism*; D019327:Copper Sulfate / Q000494:pharmacology; D006801:Humans; D008055:Lipids / Q000096:biosynthesis*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction
D002788:Cholesterol Esters; D008055:Lipids; D008077:Lipoproteins, LDL; C032629:acetyl-LDL; C099252:oxidized low density lipoprotein; D019327:Copper Sulfate; D000111:Acetylcysteine