Mining the Plasma Proteome for Insights into the Molecular Pathology of Pulmonary Arterial Hypertension
Lars Harbaum, Christopher J. Rhodes, John Wharton, Allan Lawrie, Jason H. Karnes, Ankit A. Desai, William C. Nichols, Marc Humbert, David Montani, Barbara Girerd, Olivier Sitbon, Mario Boehm, Tatyana Novoyatleva, Ralph T. Schermuly, H. Ardeschir Ghofrani, Mark Toshner, David G. Kiely, Luke S. Howard, Emilia M. Swietlik, Stefan Gräf, Maik Pietzner, Nicholas W. Morrell, Martin R. Wilkins
Abstract
Abstract Rationale Pulmonary arterial hypertension (PAH) is characterized by structural remodeling of pulmonary arteries and arterioles. Underlying biological processes are likely reflected in a perturbation of circulating proteins. Objectives To quantify and analyze the plasma proteome of patients with PAH using inherited genetic variation to inform on underlying molecular drivers. Methods An aptamer-based assay was used to measure plasma proteins in 357 patients with idiopathic or heritable PAH, 103 healthy volunteers, and 23 relatives of patients with PAH. In discovery and replication subgroups, the plasma proteomes of PAH and healthy individuals were compared, and the relationship to transplantation-free survival in PAH was determined. To examine causal relationships to PAH, protein quantitative trait loci (pQTL) that influenced protein levels in the patient population were used as instruments for Mendelian randomization (MR) analysis. Measurements and Main Results From 4,152 annotated plasma proteins, levels of 208 differed between patients with PAH and healthy subjects, and 49 predicted long-term survival. MR based on cis-pQTL located in proximity to the encoding gene for proteins that were prognostic and distinguished PAH from health estimated an adverse effect for higher levels of netrin-4 (odds ratio [OR], 1.55; 95% confidence interval [CI], 1.16–2.08) and a protective effect for higher levels of thrombospondin-2 (OR, 0.83; 95% CI, 0.74–0.94) on PAH. Both proteins tracked the development of PAH in previously healthy relatives and changes in thrombospondin-2 associated with pulmonary arterial pressure at disease onset. Conclusions Integrated analysis of the plasma proteome and genome implicates two secreted matrix-binding proteins, netrin-4 and thrombospondin-2, in the pathobiology of PAH.