Biomedical subjects

Sonia Benítez

Publications and source records attributed to Sonia Benítez.

7 recordsLinked to original sources

PubMed2004

Impaired binding affinity of electronegative low-density lipoprotein (LDL) to the LDL receptor is related to nonesterified fatty acids and lysophosphatidylcholine content.

The binding characteristics of electropositive [LDL(+)] and electronegative LDL [LDL(-)] subfractions to the LDL receptor (LDLr) were studied. Saturation kinetic studies in cultured human fibroblasts demonstrated that LDL(-) from normolipemic (NL) and familial hypercholesterolemic (FH) subjects had lower binding affinity than their respective LDL(+) fractions (P < 0.05), as indicated by higher dissociation constant (K(D)) values. FH-LDL(+) also showed lower binding affinity (P < 0.05) than NL-LDL(+) (K(D), sorted from lower to higher affinity: NL-LDL(-), 33.0 +/- 24.4 nM; FH-LDL(-), 24.4 +/- 7.1 nM; FH-LDL(+), 16.6 +/- 7.0 nM; NL-LDL(+), 10.9 +/- 5.7 nM). These results were confirmed by binding displacement studies. The impaired affinity binding of LDL(-) could be attributed to altered secondary and tertiary structure of apolipoprotein B, but circular dichroism (CD) and tryptophan fluorescence (TrpF) studies revealed no structural differences between LDL(+) and LDL(-). To ascertain the role of increased nonesterified fatty acids (NEFA) and lysophosphatidylcholine (LPC) content in LDL(-), LDL(+) was enriched in NEFA or hydrolyzed with secretory phospholipase A(2). Modification of LDL gradually decreased the affinity to LDLr in parallel to the increasing content of NEFA and/or LPC. Modified LDLs with a NEFA content similar to that of LDL(-) displayed similar affinity. ApoB structure studies of modified LDLs by CD and TrpF showed no difference compared to LDL(+) or LDL(-). Our results indicate that NEFA loading or phospholipase A(2) lipolysis of LDL leads to changes that affect the affinity of LDL to LDLr with no major effect on apoB structure. Impaired affinity to the LDLr shown by LDL(-) is related to NEFA and/or LPC content rather than to structural differences in apolipoprotein B.

Antioxidants↗

PubMed2004

Effect of simvastatin in familial hypercholesterolemia on the affinity of electronegative low-density lipoprotein subfractions to the low-density lipoprotein receptor.

The effect of simvastatin therapy on the biologic characteristics of the electronegative low-density lipoprotein (LDL) subfraction of patients with familial hypercholesterolemia (FH) was studied. Total LDL, isolated from FH plasma at 0, 3 and 6 months of simvastatin treatment, was subfractionated into electropositive LDL (LDL[+]) and electronegative LDL (LDL[-]) by anion exchange chromatography. LDL isolated from healthy normolipemic (NL) subjects was used as a control. The LDL(-) proportion was twofold higher in patients with FH than in NL subjects (17.6 +/- 1.6% vs 7.8 +/- 1.5%, respectively; p <0.05) and was progressively reduced by simvastatin therapy (15.7 +/- 1.6% at 3 months; 13.8 +/- 2.5% at 6 months; p <0.05). Both LDL subfractions from patients with FH had a higher relative cholesterol content and decreased apolipoprotein B and triglycerides than NL subfractions. Simvastatin progressively induced changes in lipid content of both LDL subfractions in patients with FH, and lipid composition was closer to these subfractions in NL subjects after 6 months of therapy. Binding displacement experiments in human fibroblasts demonstrated that LDL(-) from both groups of subjects had a lower affinity of binding to the LDL receptor that LDL(+). In addition, LDL(+) in patients with FH presented an intermediate binding affinity between LDL(-) and LDL(+) in NL subjects. Simvastatin-induced changes in LDL composition were accompanied by a progressive increase in affinity of LDL(+) and LDL(-) in patients with FH. After 6 months of therapy, LDL(+) in FH had an affinity similar to that of LDL(+) in NL subjects. The LDL(-)-induced release of chemokines interleukin-8 and monocyte chemotactic protein-1 from cultured endothelial cells was twofold higher compared with that of LDL(+). No difference in chemokine release between patients with FH and NL subjects or the effect of simvastatin were observed. We conclude that simvastatin therapy was able to modify LDL subfraction composition in subjects with FH and increase their affinity to the LDL receptor. This improvement could contribute to the observed reduction in LDL(-) proportion induced by simvastatin.

Adult↗

PubMed2004

Electronegative low-density lipoprotein.

PURPOSE OF REVIEW: The occurrence in blood of an electronegatively charged LDL was described in 1988. During the 1990s reports studying electronegative LDL (LDL(-)) were scant and its atherogenic role controversial. Nevertheless, recent reports have provided new evidence on a putative atherogenic role of LDL(-). This review focuses on and discusses these new findings. RECENT FINDINGS: In recent years, LDL(-) has been found to be involved in several atherogenic features through its action on cultured endothelial cells. LDL(-) induces the production of chemokines, such as IL-8 and monocyte chemotactic protein 1, and increases tumor necrosis factor-alpha-induced production of vascular cell adhesion molecule 1, with these molecules being involved in early phases of leukocyte recruitment. LDL(-) from familial hypercholesterolemic patients also decreases DNA synthesis and intracellular fibroblast growth factor 2 production, which may contribute to impaired angiogenesis and increased apoptosis. In addition, the preferential association of platelet-activating factor acetylhydrolase with LDL(-) has been reported, suggesting a proinflammatory role of this enzyme in LDL(-). SUMMARY: Recent findings suggest that LDL(-) could contribute to atherogenesis via several mechanisms, including proinflammatory, proapoptotic and anti-angiogenesis properties. Further studies are required to define the role of LDL(-) in atherogenesis more precisely and to clarify mechanisms involved in endothelial cell activation.

Animals↗

PubMed2003

Platelet-activating factor acetylhydrolase is mainly associated with electronegative low-density lipoprotein subfraction.

BACKGROUND: Electronegative LDL [LDL(-)], a modified subfraction of LDL present in plasma, induces the release of interleukin-8 and monocyte chemotactic protein-1 from cultured endothelial cells. METHODS AND RESULTS: We demonstrate that platelet-activating factor acetylhydrolase (PAF-AH) is mainly associated with LDL(-). LDL(-) had 5-fold higher PAF-AH activity than the nonelectronegative LDL subfraction [LDL(+)] in both normolipemic and familial hypercholesterolemic subjects. Western blot analysis after SDS-PAGE confirmed these results, because a single band of 44 kDa corresponding to PAF-AH appeared in LDL(-) but not in LDL(+). Nondenaturing polyacrylamide gradient gel electrophoresis demonstrated that PAF-AH was bound to LDL(-) regardless of LDL size. In accordance with the above findings, nonesterified fatty acids, a cleavage product of PAF-AH, were increased in LDL(-) compared with LDL(+). CONCLUSIONS: The high PAF-AH activity observed in LDL(-) could be related to the proinflammatory activity of these lipoproteins toward cultured endothelial cells.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2003

Electronegative LDL of FH subjects: chemical characterization and induction of chemokine release from human endothelial cells.

Electronegative LDL (LDL(-)) constitutes a plasma subfraction of LDL with proinflammatory properties. Its proportion is increased in familial hypercholesterolemia (FH); however, the characteristics of LDL(-) isolated from FH subjects have not been previously studied. In this work, the composition, oxidative status, and inflammatory capacity on endothelial cells of LDL(-) from FH and normolipemic (NL) subjects were evaluated. LDL(-) from FH was relatively enriched in esterified and free cholesterol and triglyceride, and had lower apoB and phospholipid content compared with the non-electronegative fraction (LDL(+)). LDL(-) also contained increased amounts of apoE, apoC-III, sialic acid, and non-esterified fatty acids (NEFAs). The same was observed in NL subjects, except that esterified cholesterol and phospholipid were similar in LDL(-) and LDL(+). No difference was observed between the two fractions concerning malondialdehyde, fatty acid hydroxides, and antioxidants, thereby indicating the absence of increased oxidation of LDL(-) compared with LDL(+). When LDL(-) (100 mg/l) from NL and FH subjects was incubated for 24 h with human umbilical vein endothelial cells (HUVECs), interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1) increased twofold in the culture medium compared with LDL(+). Vascular cell adhesion molecule 1 (VCAM-1) expression was not increased by LDL(-). Our data indicate that LDL(-) from FH or NL subjects shows no evidence of increased oxidative modification compared to LDL(+); however, LDL(-) induces twofold the release of chemokines by endothelial cells. This effect, which may contribute to leukocyte recruitment and promote atherogenesis, may be greater in FH subjects in which LDL(-) can be up to eightfold higher than in NL subjects.

Blotting, Western↗

PubMed2002

Changes in low-density lipoprotein electronegativity and oxidizability after aerobic exercise are related to the increase in associated non-esterified fatty acids.

The immediate effects of intense aerobic exercise on the composition and oxidizability of low- (LDL) and high-density lipoproteins (HDL) were studied in 11 male athletes. Plasma parameters known to affect lipoprotein oxidizability were also evaluated. Lipophilic antioxidants, including alpha-tocopherol and carotenoids, paraoxonase and malondialdehyde (MDA) in plasma remained unchanged after exercise. Increases in the concentration of uric acid, bilirubin and ascorbic acid after the race resulted in a significant increase in total antioxidant serum capacity. LDL, but not HDL, increased its "in vitro"-induced susceptibility to oxidation and the proportion of electronegative LDL (LDL-). The ability of HDL to inhibit the oxidation of LDL remained unchanged after exercise. The enhanced oxidizability of LDL was not explained by increments in its aldehyde content or by decrements in antioxidants. The major compositional change in LDL was an increase in non-esterified fatty acid (NEFA) content (from 4.00+/-1.24 to 19.00+/-14.18 mol NEFA/mol apoB). NEFA also increased in plasma and HDL. "In vitro" experiments showed that incubation of LDL with increasing amounts of NEFA induced a concentration-dependent increase in the proportion of LDL-. Moreover, a slightly increased NEFA content in LDL (15-50 mol NEFA/mol apoB) induced higher susceptibility to oxidation. These "in vitro" results concur with those observed in LDL obtained from athletes after exercise, i.e. a concentration of approximately 20 mol NEFA/mol apoB increased LDL oxidizability and LDL- proportion. We conclude that changes in the qualitative characteristics of LDL after exercise were unrelated to oxidative stress, but were related to the increase in LDL-associated NEFA content.

Adult↗

PubMed2002

Density distribution of electronegative LDL in normolipemic and hyperlipemic subjects.

The density distribution of electronegative LDL [LDL(-)], a cytotoxic and inflammatory fraction of LDL present in plasma, was studied in 10 normolipemic (NL), 6 FH, and 11 hypertriglyceridemic (HTG) subjects. Six LDL subclasses of increased density (LDL1 to LDL6) were isolated by density-gradient ultracentrifugation (DGU). NL and FH subjects showed prevalence of light LDL, whereas HTG subjects showed prevalence of dense LDL. LDL(-) proportion was determined from total LDL or LDL-density subclasses by anion-exchange chromatography. LDL from FH patients had increased LDL(-) (35.1 +/- 9.9%) compared with LDL from NL and HTG subjects (9.4 +/- 2.3% and 12.3 +/- 4.3%, respectively). Most LDL(-) was contained in dense subclasses in NL (LDL4-6, 67.7 +/- 3.1%) whereas most of LDL(-) from FH patients were contained in light LDL subclasses (LDL1-3) (86.2 +/- 1.6%). In these subjects, simvastatin therapy decreased LDL(-) to 28.2 +/- 6.7% and 21.2 +/- 5.6% at 3 and 6 months of treatment, respectively, due mainly to decreases in light LDL subclasses. In HTG subjects, half LDL(-) was contained in dense LDL subclasses (LDL4-6, 46.1 +/- 2.0%). Non-denaturing acrylamide gradient gel electrophoresis concurred with DGU data, as LDL(-) from NL showed a single band of lower size than non-electronegative LDL [LDL(+)], whereas LDL(-) from FH and HTG presented bands of greater size than its respective LDL(+). These results reveal the existence of light and dense LDL(-), indicate that hyperlipemia could promote the formation of light LDL(-) and suggest that LDL(-) could have different origins.

Adult↗