Mechanism of high-density lipoprotein subfractions inhibiting copper-catalyzed oxidation of low-density lipoprotein.
OBJECTIVE
To investigate the role of HDL subfractions, HDL2 and HDL3, on the oxidation of LDL catalyzed by 5 microM Cu2+ ion, and to illustrate the mechanism of the generation of conjugated diene and thiobarbituric acid reactive substances (TBARS) during LDL oxidation.


METHODS
LDL was incubated for 8 h with 5 microM Cu2+ ion in phosphate-buffered saline (PBS) alone, or in the presence of HDL2, HDL3, HSA, BSA, or transferrin. Meantime, LDL was incubated for 24 h with 10 microM Ni2+ ions in PBS. The amount of conjugated diene and TBARS in each sample of LDL were measured.


RESULTS
(a) HDL2 and HDL3 could inhibit the generation of conjugated diene, but could not inhibit the generation of TBARS; (b) the transferrin containing HDL3 shows the ability of inhibiting the generation of both conjugated diene and TBARS; (c) the transferrin presented in blood exhibits the inhibitory effect on the generation of conjugated diene and TBARS, however, when the transferrin is saturated with Fe3+ ion, it could not inhibit the generation of TBARS; (d) HSA and BSA could prevent the generation of conjugated diene and TBARS; (e) Ni2+ ion could induce the generation of conjugated diene, but the amount of TBARS was much smaller than that induced by Cu2+ ion.


CONCLUSIONS
HDL2 and HDL3 play important role in the copper-catalyzed oxidation of LDL; it is absolutely necessary to require chelation of Cu2+ ion for inhibiting generation of TBARS; whereas, inhibition of conjugated diene can be fulfilled either by chelating Cu2+ ion, or the free radicals scavenger.
Huang
J M
JM
Chemistry Department, Fudan University, Shanghai, P.R. China. ZXHUANG@FUDAN.EDU.CN
Huang
Z X
ZX
Zhu
W
W
D001059:Apoproteins / Q000378:metabolism / Q000494:pharmacology; D003300:Copper / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D053439:Lipoproteins, HDL2; D053440:Lipoproteins, HDL3; D008077:Lipoproteins, LDL / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D009532:Nickel / Q000378:metabolism / Q000494:pharmacology; D010084:Oxidation-Reduction; D012709:Serum Albumin / Q000378:metabolism / Q000494:pharmacology; D012710:Serum Albumin, Bovine / Q000378:metabolism / Q000494:pharmacology; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism / Q000494:pharmacology
D001059:Apoproteins; D008075:Lipoproteins, HDL; D053439:Lipoproteins, HDL2; D053440:Lipoproteins, HDL3; D008077:Lipoproteins, LDL; D012709:Serum Albumin; D017392:Thiobarbituric Acid Reactive Substances; D014168:Transferrin; C028284:apotransferrin; D012710:Serum Albumin, Bovine; D003300:Copper; D009532:Nickel