Comparison of endothelin-1 levels in human plasma from human coronary arteries measured by enzyme linked immunosorbent assay and Olink high-throughput proteomics platform

Endothelin-1 (ET-1) antagonists are increasingly being approved for new treatments for cardiovascular disease, where elevated ET-1 levels contribute to increased vasoconstriction. Further therapeutic targets, including coronary artery disease, are under investigation. The Olink Explore 3072 Proximity Extension Assay platform enables multiplexed high throughput measurement of ~3000 plasma proteins, from minimal (≤6µl) sample volumes. However, it is not known if the two oligonucleotide‑tagged antibodies raised against preproET-1₁-₂₁₂, used in this Olink assay, specifically measure biologically active ET-1 or the other inactive EDN1-encoded peptides, also secreted by human endothelial cells. Paired plasma samples from 29 patients with coronary artery disease were obtained, using a specialised intra-coronary sampling catheter, designed to obtain site specific biochemical information from within coronary arteries. We compared ET-1 concentrations measured with an ET-1 specific ELISA, demonstrated to have no cross reactivity with other EDN1-encoded peptides versus values obtained using Olink Explore platform. Olink-measured ET-1 correlated significantly with ELISA-derived ET-1 levels (r=0.53, p=0.003), and Olink values predicted ELISA results. Olink ET-1 concentrations also correlated with ETB receptor levels (r=0.40, p< 0.05). These findings indicate that the Olink Explore platform can detect relative changes in biologically active ET-1, supporting its use as a biomarker tool in clinical and translational studies.