Electronegative ApoCIII-Rich HDL promotes cellular damage and vascular aging
Authors: Hsu W L , Tsai M H , Chung C P , Vadhan A , Wei W Y , Akyol O , Chiang H H , Kraler S , Luscher T F , Chen C H 
Published: October 2024

Abstract

Background
Experimental studies attributing HDL a cardioprotective effect are challenged by well-designed randomized controlled trials showing largely neutral results, which might be related to more recent observations that certain HDL particles exert detrimental effects. This study explores the effects of electronegative HDL on cellular damage and vascular aging. Using anion-exchange chromatography, HDL was divided into five subclasses (H1 to H5) based on increasing electronegativity. Compared to the health-promoting H1, the most electronegative subclass, H5 contains significantly higher levels of ApoCIII and triglycerides (TG).

Purpose
Herein, we aim to explore the cellular and molecular mechanisms underpinning H5-induced pathology in human umbilical vein vascular endothelial cells (HUVECs), which may accelerate vascular aging preceding the development of atherosclerotic cardiovascular disease (ASCVD).

Methods
H1 and H5 were isolated from patients with metabolic syndrome (MetS). To gauge the impact of H5 on vascular integrity, HUVECs were treated with solvent, H1, or H5 at concentrations of 25, 50, or 100 µg/mL. Cell viability and apoptosis were evaluated using the MTT assay and PI/Calcein fluorescent staining, respectively. Immunofluorescence staining and immunoblotting, focusing on 8-oxodG, P53, and β-gal, proxies of DNA damage and cellular senescence, were performed. Senescence-associated secretory phenotype (SASP) analysis was done to elucidate the senescent mechanism. By harnessing Mitosox imaging reactive oxygen species (ROS) synthesis was monitored. Finally, unbiased lipid- and transcriptomics were used to identify lipid components potentially involved in H5 signaling.

Results
As compared to controls, MetS patients exhibited more electronegative HDL particles, as indicated by increased H5 (1.604±0.410% vs 4.598±4.712%, P=0.0016). Remarkable elevations were noted in individuals with severe clinical complications, as shown in the representative patient with left ventricular hypertrophy, chronic coronary syndrome, and heart failure (Fig. 1). In HUVECs, H5 but not H1 reduced cell viability and increased apoptosis in a concentration-dependent manner. In parallel, H5 but not H1 induced cell aging, ROS production, and DNA damage, with SASP cytokines including IL-1β, IL-6, CCL2, TNF-α, and γH2AX (Fig. 1). Notably, compared to H1, H5 exhibited high contents of various TG species, impairing H5’s anti-inflammatory and antioxidant capacities, along with reductions in several phosphatidylcholines that may constitute essential cell membrane structural components, as evidenced by lipidomic studies (Fig. 2).

Conclusion
H5, the most electronegative and dysfunctional HDL subfraction, is capable of inducing DNA damage, oxidative stress, and senescence in vascular ECs. Its notable elevation in patients with MetS highlights a previously unrecognized etiology, shedding light on how electronegative HDL may contribute to and expedite ASCVD.Fig 1Fig 2