Abstract Body: BACKGROUND: High plasma lipoprotein(a) (Lp(a)) is a risk factor for cardiovascular diseases including atherosclerosis and calcific aortic valve disease. The mechanisms by which Lp(a) acts remain to be clarified, however. Lp(a) elicits a proinflammatory phenotype in endothelial cells (ECs), with accompanying changes in metabolism towards glycolytic pathways. To further explore these mechanisms, and to compare the response of human coronary artery ECs (HCAEC) and human aortic valve ECs (HAVEC), we exposed these cells to purified Lp(a) in vitro and undertook transcriptomic and metabolic analyses. We hypothesize that Lp(a) induces a proinflammatory and oxidative stress response in ECs.

METHODS: Primary ECs were stimulated with 250 nmol/L Lp(a) or vehicle control for 2, 4, 8, and 16 hours (HCAEC) or 4, 8, and 16 hours (HAVEC). RNA was isolated, and global gene expression changes were examined by RNA-Seq (n=1). qRT-PCR was performed to validate Lp(a) effects on expression of selected genes. Additionally, the effect of Toll-like receptor (TLR) 2 and 4 and CD36 inhibition on Lp(a)-induced gene expression changes was assessed (n=3). Mitochondrial activity was measured by Seahorse assay, and ROS generation was quantified using commercially available assays.

RESULTS: RNA-seq analysis identified significant changes in HCAEC and HAVEC gene expression after Lp(a) treatment, with 1915 and 444 genes, respectively, identified as differentially expressed at 16 hours. KEGG pathway analysis showed significant (FDR < 0.05) enrichment in metabolic and proinflammatory signaling pathways, with distinct yet overlapping patterns in HCAEC and HAVEC. Interestingly, the most upregulated gene in both cell types was that encoding the stress response protein heme oxygenase-1 (HMOX-1), which was maximally induced by 50-fold in HCAEC and 7.5-fold in HAVEC. Moreover, Lp(a) increased mitochondrial activity, with a shift towards higher glycolysis, ROS generation, and ER stress in HCAEC. Lp(a)-induced expression of interleukin (IL)1a and selectin (SELE), but not HMOX1, was significantly (p<0.05) reduced with the inhibition of TLR2 and 4.

CONCLUSIONS: The relationship between Lp(a) and HMOX-1, ROS and metabolic stress, as well as TLR-induced proinflammatory pathways, illuminates the mechanisms by which Lp(a) induces endothelial dysfunction in cardiovascular disease, creating pathways for the development of new disease prevention and management strategies.