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Proteomic analysis of electronegative low-density lipoprotein.

ABSTRACT: Low density lipoprotein is a heterogeneous group of lipoproteins that differs in lipid and protein composition. One copy of apolipoprotein (apo)B accounts for over 95% of the LDL protein, but the presence of minor proteins could disturb its biological behavior. Our aim was to study the content of minor proteins in LDL subfractions separated by anion exchange chromatography. Electropositive LDL [LDL(+)] is the native form, whereas electronegative LDL [LDL?] is a minor atherogenic fraction present in blood. LC-ESI MS/MS analysis of both LDL fractions identified up to 28 different proteins. Of these, 13 proteins, including apoB, were detected in all the analyzed samples. LDL? showed a higher content of most minor proteins. Statistical analysis of proteomic data indicated that the content of apoE, apoA-I, apoC-III, apoA-II, apoD, apoF, and apoJ was higher in LDL? than in LDL(+). Immunoturbidimetry, ELISA, or Western blot analysis confirmed these differences. ApoJ and apoF presented the highest difference between LDL(+) and LDL? (>15-fold). In summary, the increased content of several apolipoproteins, and specifically of apoF and apoJ, could be related to the physicochemical characteristics of LDL?, such as apoB misfolding, aggregation, and abnormal lipid composition.

SUBMITTER: Bancells C

PROVIDER: S-EPMC2975723 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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Proteomic analysis of electronegative low-density lipoprotein.

Bancells Cristina C Canals Francesc F Benítez Sònia S Colomé Nuria N Julve Josep J Ordóñez-Llanos Jordi J Sánchez-Quesada José Luis JL

Journal of lipid research 20100810 12

Low density lipoprotein is a heterogeneous group of lipoproteins that differs in lipid and protein composition. One copy of apolipoprotein (apo)B accounts for over 95% of the LDL protein, but the presence of minor proteins could disturb its biological behavior. Our aim was to study the content of minor proteins in LDL subfractions separated by anion exchange chromatography. Electropositive LDL [LDL(+)] is the native form, whereas electronegative LDL [LDL⁻] is a minor atherogenic fraction present ...[more]

PMID: 20699421

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Project description:ObjectivesIncreased plasma C-reactive protein (CRP) levels are associated with the occurrence and severity of acute coronary syndrome. We investigated whether CRP can be generated in vascular endothelial cells (ECs) after exposure to the most electronegative subfraction of low-density lipoprotein (LDL), L5, which is atherogenic to ECs. Because L5 and CRP are both ligands for the lectin-like oxidized LDL receptor-1 (LOX-1), we also examined the role of LOX-1.Methods and resultsPlasma LDL samples isolated from asymptomatic hypercholesterolemic (LDL cholesterol [LDL-C] levels, 154.6±20 mg/dL; n?=?7) patients and normocholesterolemic (LDL-C levels, 86.1±21 mg/dL; P<0.001; n?=?7) control individuals were chromatographically resolved into 5 subfractions, L1-L5. The L5 percentage (L5%) and the plasma L5 concentration ([L5] ?=? L5% × LDL-C) in the patient and control groups were 8.1±2% vs. 2.3±1% (P<0.001) and 12.6±4 mg/dL vs. 1.9±1 mg/dL (P<0.001), respectively. In hypercholesterolemic patients treated with atorvastatin for 6 months (10 mg/day), [L5] decreased from 12.6±4 mg/dL to 4.5±1.1 mg/dL (P?=?0.011; n?=?5), whereas both [L5] and L5% returned to baseline levels in 2 noncompliant patients 3 months after discontinuation. In cultured human aortic ECs (HAECs), L5 upregulated CRP expression in a dose- and time-dependent manner up to 2.5-fold (P<0.01), whereas the least electronegative subfraction, L1, had no effect. DiI-labeled L1, internalized through the LDL receptor, became visible inside HAECs within 30 seconds. In contrast, DiI-labeled L5, internalized through LOX-1, became apparent after 5 minutes. L5-induced CRP expression manifested at 30 minutes and was attenuated by neutralizing LOX-1. After 30 minutes, L5 but not L1 induced reactive oxygen species (ROS) production. Both L5-induced ROS and CRP production were attenuated by ROS inhibitor N-acetyl cysteine.ConclusionsOur results suggest that CRP, L5, and LOX-1 form a cyclic mechanism in atherogenesis and that reducing plasma L5 levels with atorvastatin disrupts the vascular toxicity of L5.

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Proteomic analysis of electronegative low-density lipoprotein.

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Proteomic analysis of electronegative low-density lipoprotein.

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