Reaction of phosphatidylcholine hydroperoxide in human plasma: the role of peroxidase and lecithin:cholesterol acyltransferase.
In order to elucidate the reason why phosphatidylcholine hydroperoxide is unstable in human plasma, 1-palmitoyl-2-linoleoylphosphatidylcholine hydroperoxide (PLPC-OOH) was incubated aerobically in human plasma at 37 degrees C, and its decomposition products were measured. The major product was the corresponding alcohol (PLPC-OH) and this reduction probably occurred by an enzymatic process since no acceleration in ascorbate depletion and no significant decrease in other plasma antioxidants were observed upon addition of PLPC-OOH. Cholesteryl linoleate hydroperoxide and its alcohol (Ch18:2-OH) were also detected as minor products. Similarly, 1-stearoyl-2-arachidonoylphosphatidylcholine hydroperoxide gave its alcohol (SAPC-OH) as a major product and cholesteryl arachidonate hydroperoxide and its hydroxide (Ch20:4=OH) as minor products. These oxidized cholesteryl esters are likely to be produced by the action of lecithin:cholesterol acyltransferase (LCAT) present in high-density lipoprotein (HDL) since (a) incubation of PLPC-OH and SAPC-OH in human plasma gave Ch18:2-OH and Ch20:4-OH, respectively, (b) isolated human HDL converted PLPC-OH to Ch18:2 OH and SAPC-OH to Ch20:4-OH while isolated human low-density lipoprotein was inactive for this conversion, and (c) formation of oxidized cholesteryl esters in plasma and HDL was inhibited by the LCAT inhibitor 5,5'-dithiobis(2-nitrobenzoic acid). A possible beneficial role of LCAT for converting phosphatdylcholine hydroperoxide to cholesteryl ester hydroperoxide is also discussed.
Nagata
Y
Y
Research Center for Advanced Science and Technology, University of Tokyo, Japan.
Yamamoto
Y
Y
Niki
E
E
D000328:Adult; D002788:Cholesterol Esters / Q000097:blood; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood; D008297:Male; D010544:Peroxidases / Q000097:blood*; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000037:antagonists & inhibitors / Q000097:blood*; D010713:Phosphatidylcholines / Q000097:blood*; D010741:Phospholipases A / Q000097:blood
D002788:Cholesterol Esters; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D010713:Phosphatidylcholines; C057590:phosphatidylcholine hydroperoxide; C055402:1-palmitoyl-2-linoleoylphosphatidylcholine; D010544:Peroxidases; D007862:Phosphatidylcholine-Sterol O-Acyltransferase; D010741:Phospholipases A