Electronegative remnant lipoproteins drive endothelial and immune cytotoxicity: pathogenic effects of i5 and total Lp5 subfractions
O Akyol, F W Ouyang, H H Chiang, C Y Yang, A R Burns, C ChenAbstract
Background
Remnant lipoproteins contribute to atherosclerosis, yet their functional heterogeneity remains poorly defined. Electronegative lipoproteins exhibit potent pro-atherogenic properties, but the pathogenic role of highly electronegative remnant subfractions, particularly IDL-derived I5 and total lipoprotein-derived Lp5, has not been systematically characterized.
Purpose
To determine whether the most electronegative remnant subfractions (I5 and Lp5) exert greater cytotoxic effects on vascular endothelial and immune cells compared with their least electronegative counterparts (I1 and Lp1).
Methods
IDL and total lipoproteins were fractionated by anion-exchange chromatography into five charge-based subfractions (I1-I5 and Lp1-Lp5). Charge density was verified by agarose gel electrophoresis. Bovine aortic endothelial cells (BAEC) and THP-1 monocytes were exposed to graded concentrations of each subfraction for 24 hours. Cell viability was quantified using trypan blue exclusion and fluorescent cytometric assays.
Results
Chromatographic and electrophoretic analyses confirmed markedly increased negative charge in I5 and Lp5 relative to I1 and Lp1. In BAEC, both I5 and Lp5 induced significant, dose-dependent reductions in cell viability, whereas I1 and Lp1 had minimal effects. Similarly, in THP-1 monocytes, I5 and Lp5 provoked substantially greater cytotoxic and inflammatory responses. Across all experimental conditions, electronegative remnant subfractions consistently demonstrated greater potency in inducing cell death than their less electronegative counterparts.
Conclusion
Highly electronegative remnant lipoproteins (I5 and Lp5) exhibit markedly enhanced cytotoxicity toward endothelial and immune cells. These findings identify electronegativity as a critical determinant of remnant lipoprotein pathogenicity. Targeting electronegative remnant fractions may provide a more precise strategy for attenuating vascular injury than approaches focused solely on total lipid levels.Figure 1Figure 2