Oxidation of low density lipoproteins leads to disturbance of their binding with alpha-tocopherol.
The dynamics of binding of exogenous alpha-tocopherol (alpha-T) added to native or oxidatively modified LDLs (LDLs or oxLDLs) were investigated. Venous blood from 31 clinically healthy blood donors (15 males and 16 females) was used. LDLs were isolated by density gradient ultracentrifugation. LDLs were oxidized in vitro by CuSO4. LDLs or oxLDLs were enriched with exogenous alpha-T (initial concentrations: 0; 10; 20; 50; or 100 nmol per mg protein). The contents of alpha-T in LDLs or in oxLDLs were measured by HPLC. Lag-phase of LDL oxidation before or after saturation with alpha-T was recorded. Correlation analysis of the lag-phase of LDL oxidation and alpha-T content in LDLs was carried out by the method of Esterbauer et al. The experimental results demonstrated that: (i) alpha-T was incorporated into native LDLs to a higher extent as compared to oxLDLs. (ii) A saturation of LDLs and oxLDLs with alpha-T was observed. (iii) A positive correlation was observed between the duration of the lag-phase of LDL oxidation in vitro and the content of alpha-T in LDLs. (iv) Based on LDL saturation with alpha-T, the persons could be classified in two groups: LDLs from group I of 26 persons were found to incorporate exogenous alpha-T to the extent of 1.8 to 3 times its initial concentration; LDLs from group II of 5 persons incorporated little or no exogenous alpha-T. In the first group, oxidation of LDLs lead to a considerable decrease in alpha-T dependent variable k and to a moderate reduction of alpha-T-independent variable alpha in the equation of Esterbauer et al.: lag-phase = k.[alpha-tocopherol]+alpha. In the second group, oxidation of LDLs lead to insignificant changes in k, as well as in a. (v) According to the levels of k and a the native LDLs from the second group of 5 persons were very close to oxLDLs from the first group of 26 persons. Presumably, native LDLs from the second group of persons were initially oxidatively modified, and probably this will be a risk group in relation to atherogenic disorders.
Bakalova
R A
RA
Department of Medical Physics and Biophysics, Sofia Medical University, Bulgaria.
Goudev
A R
AR
Zhelev
Z Z
ZZ
Nachev
C
C
Ribarov
S R
SR
D000328:Adult; D019327:Copper Sulfate / Q000737:chemistry / Q000378:metabolism; D005260:Female; D006801:Humans; D008077:Lipoproteins, LDL / Q000737:chemistry* / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D011485:Protein Binding; D014810:Vitamin E / Q000737:chemistry* / Q000378:metabolism*
D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein; D014810:Vitamin E; D019327:Copper Sulfate