NCOA7 Deficiency Reprograms Lysosomal Behavior and Sterol Metabolism to Promote Endothelial Dysfunction and Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is an enigmatic vascular disorder characterized by complex pulmonary vessel remodeling. Barriers to effective therapies have included a relatively low disease prevalence and pathogenic, multisystem mechanisms whose pathways remain incompletely defined. To better understand the molecular origins of PAH, we and our colleagues performed the largest, unbiased metabolomics screen of more than 2,000 PAH patients and identified a cluster of oxysterols and bile acids that had strong associations to clinical parameters of disease. A mechanistic role, however, for oxysterols and bile acids in the pathogenesis of PAH has never been established. Recently, lysosomes have been implicated as central mediators of sterol homeostasis within the cell. Accordingly, we identified the nuclear receptor co-activator 7 (NCOA7) as a molecule of interest, as previous literature has documented a role in endolysosomal trafficking. As such, we leveraged parallel metabolomics and orthogonal genomics data from The FINRISK Study of nearly 8,000 people to discover that candidate metabolites were negatively associated with an allelic variant at SNP rs11154337 in NCOA7. We then confirmed that proinflammatory stimuli integrate onto NF-κB to control the expression of NCOA7 in an allele-specific manner. Knockdown of NCOA7 resulted in lysosomal dysfunction and sterol accumulation, thereby resulting in the production of oxysterol species through cholesterol 25-hydroxylase (CH25H). Production of oxidized sterol species immunoactivated the endothelium as noted by increased vascular cell adhesion molecule 1 (VCAM1) and immune cell attachment. In support of this mechanism, we confirmed in an angioproliferative mouse model that the loss of NCOA7 worsened hemodynamic indices of disease. Furthermore, we found activation of the CH25H pathway by vessel staining and subsequent VCAM1 upregulation and immune infiltration, which was also supported by the elevation of downstream oxidized sterols in the serum of these animals. Overall, the totality of our work serves as one of the first successful examples of multi-omics integration in the identification of a causal variant, maps the first mechanistic explanation of sterol aberrations in PAH, and implicates oxidized lipid species and NCOA7 as potential targets for biomarker development and therapeutic targeting.