Va. Folcik et Mk. Cathcart, PREDOMINANCE OF ESTERIFIED HYDROPEROXY-LINOLEIC ACID IN HUMAN MONOCYTE-OXIDIZED LDL, Journal of lipid research, 35(9), 1994, pp. 1570-1582
Low density lipoprotein that was oxidized by activated human monocytes
was analyzed to determine the identity of oxidized fatty acids presen
t and the conditions required for their formation. The oxidized lipids
were also analyzed under conditions allowing preservation of their ox
idation state. Using reversed-phase high performance liquid chromatogr
aphy (HPLC) analysis of native and saponified lipid extracts of oxidiz
ed low density lipoprotein (LDL), we found that the major fatty acid o
xidation product was esterified hydroperoxyoctadecadienoic acid (HPODE
), the oxidized product of the most abundant polyunsaturated fatty aci
d in human LDL, linoleic acid. Although some esterified hydroxyoctadec
adienoic acid (HODE) was also detected, the reduction of HPODE to HODE
did not appear to be monocyte-dependent, Essentially all of the HPODE
was found to be esterified with the majority being esterified to chol
esterol followed by phospholipids and generally following the abundanc
e of esterified linoleic acid within the lipid classes. The percent of
cholesteryl linoleate converted to cholesteryl HPODE and cholesteryl
HODE at the end of the 24-h incubation was determined to be approximat
ely 13.5%. The formation of oxidized esterified linoleic acid in the L
DL was shown to require immunological activation of the human monocyte
s, a previously observed requirement for general LDL oxidation in this
culture system. The oxidized esterified linoleic acid was present in
the supernatant with the LDL and was not cell-associated. HPODE format
ion on LDL was prevented by including superoxide dismutase (SOD) or ei
cosatetraynoic acid (ETYA) during the 24-h coincubation of activated m
onocytes with LDL whereas indomethacin was without effect. The analysi
s of the lipid oxidation products in oxidized LDL can provide insight
into the mechanisms involved in oxidation of LDL by activated human mo
nocytes.