Lipoprotein(a) regulates vascular redox state and inflammatory response in patients with coronary artery disease

Abstract Background Circulating Lipoprotein(a) (Lp(a)) is associated with cardiovascular disease, and over 90% of its variation in plasma is genetically determined. However, neither the causal nature of this association nor the underlying mechanisms are fully documented. Purpose We explored the hypothesis that Lp(a) triggers atherogenesis by dysregulating vascular redox-sensitive inflammatory state. Methods 1027 patients with advanced coronary artery disease (CAD) undergoing cardiac surgery were genotyped and a genetic signature (LPA) determining Lp(a) levels was generated. RNA-sequencing and vascular superoxide (O2.-) measurements were performed in internal mammary arteries (IMA), and the contribution of NADPH-oxidases and uncoupled endothelial nitric oxide synthase (eNOS) were determined. Patients were followed up for a median of 5.07 years. Results A genetic screening identified 7 SNPs (LPA) that were associated with increased Lp(a) plasma levels (A). Patients in the alternative LPA variant group, as well as patients with higher plasma Lp(a) levels, had significantly higher basal arterial O2.-. Patients with diabetes had significantly lower plasma Lp(a) compared to non-diabetics and the association between plasma Lp(a) and arterial O2.- was driven by non-diabetic patients. The effect of Lp(a) on vascular redox state was primarily due to eNOS uncoupling, resulting from reduced vascular tetrahydrobiopterin (BH4) bioavailability. Indeed, patients in the alternative LPA variant group or with higher plasma Lp(a) levels had a greater arterial eNOS-derived (LNAME-inhibitable) O2.- production (B,C). Levels of eNOS essential cofactor BH4 (defined by the ratio of plasma BH4 to its oxidation product BH2) were lower in patients with higher plasma Lp(a) levels (D). There was no significant impact of Lp(a) variability on vascular NADPH oxidase-derived O2.-. RNA sequencing of arterial tissue revealed dysregulation of nitrosative and inflammatory signalling in patients with high Lp(a), although there was no association with systemic biomarkers of inflammation (i.e. hsCRP) or oxidative stress (i.e. malondialdehyde). Finally, both LPA and high plasma Lp(a) were associated with elevated risk for cardiovascular mortality (E,F). When the cox regression models were additionally corrected for arterial O2.- production, both the models for the LPA genetic signature (HR[95% CI]=2.053[0.180-23.428], p=0.563) and plasma Lp(a) (HR[95% CI]=1.700[0.325-8.885], p=0.529) lost significance. This implies that redox-sensitive inflammatory signalling may be a link between Lp(a) and cardiovascular risk. All above associations were independent from plasma ApoB. Conclusions This study demonstrates for the first time that a genetically determined increase in plasma Lp(a) results in dysregulated vascular redox/nitrosative signalling in patients with atherosclerosis, revealing new therapeutic opportunities in cardiovascular prevention.