Regulation of 12-hydroxyeicosatetraenoic acid synthesis by acetyl-LDL in mouse peritoneal macrophages.
The mechanism for the regulation of 12-hydroxyeicosatetraenoic acid (12-HETE) production by cholesterol-rich macrophages was investigated. beta-VLDL and acetyl-LDL, lipoproteins which result in cholesterol accumulation in macrophages, stimulated 12-HETE secretion. Lipoproteins which do not induce cholesterol accumulation, such as low- and high-density lipoproteins, did not. Cell-free homogenates from cholesterol-rich macrophages had significantly more 12-lipoxygenase activity than homogenates from unmodified cells. Preincubating homogenates prepared from unmodified macrophages with acetyl-LDL, LDL or multilamellar liposomes containing total lipids from acetyl-LDL but not apoproteins significantly increased 12-lipoxygenase activity. This stimulatory effect was caused by the phospholipid moiety of the lipoprotein. 12-HETE synthesis was not increased in macrophages enriched 6-fold in unesterified cholesterol. Acetyl-LDL stimulated 12-HETE synthesis in macrophages in which cholesteryl ester accumulation was prevented by inhibiting acylcoenzyme A:cholesterol acyltransferase activity. When binding of acetyl-LDL to its receptor was decreased by increasing concentrations of dextran sulfate, or when lysosomal metabolism of the lipoprotein was prevented by chloroquine, 12-HETE production significantly decreased. Moreover, the combination of inhibiting acetyl-LDL binding and degradation completely blocked the stimulation of 12-HETE synthesis by acetyl-LDL. The data indicate that acetyl-LDL must enter the macrophage and be partially degraded to regulate 12-HETE synthesis. The regulation is independent of cholesterol accumulation but is related to the entering lipoprotein phospholipid.
Mathur
S N
SN
Department of Internal Medicine, University of Iowa, Iowa City 52242.
Albright
E
E
Field
F J
FJ
D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D000818:Animals; D002738:Chloroquine / Q000494:pharmacology; D016264:Dextran Sulfate; D003911:Dextrans / Q000494:pharmacology; D006893:Hydroxyeicosatetraenoic Acids / Q000096:biosynthesis*; D008075:Lipoproteins, HDL / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D051379:Mice; D010537:Peritoneum / Q000166:cytology
D003911:Dextrans; D006893:Hydroxyeicosatetraenoic Acids; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; C032629:acetyl-LDL; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D002738:Chloroquine; D016264:Dextran Sulfate