Abstract Body (Do not enter title and authors here): Background: Pulmonary hypertension (PH) is a fatal pulmonary vascular disease characterized by progressive increase in pulmonary arterial pressure, which leads to right ventricular failure and death. Pulmonary artery endothelial cell (PAEC) dysfunction and smooth muscle cell (PASMC) proliferation are two major hallmarks of PH, which induce inflammation and pulmonary vascular remodeling. The role of oxidized lipids in the pathogenesis of PH has been emerging, and our lab was the first to show that a diet enriched in a single oxidized fatty acid, 15-Hydroxyeicosatetraenoic Acid (15-HETE), is sufficient to cause PH in wild-type mice. However, the molecular mechanism underlying the causal role of dietary oxidized lipids in the development of PH remained unknown.
Research Hypothesis: We hypothesize that dietary 15-HETE causes PH by promoting Stearoyl-CoA Desaturase-1 (Scd1) mediated PAEC and PASMC dysfunction.
Approach: C57BL/6 mice were fed with 15-HETE diet for three weeks to develop PH. We utilized RNA-Seq analysis on FACS-isolated enterocytes, from control and 15-HETE diet-fed mice to identify differences in genes involved in lipid metabolism. Lipidyzer™ analysis was used to measure the level of lipids in plasma. In vitro experiments were performed using human PAEC and PASMC.
Results: Mice fed a 15-HETE-enriched diet for 3 weeks developed PH as right ventricular systolic pressure was significantly higher than chow-fed controls. RNA-seq of FACS-isolated enterocytes identified Scd1 as a novel gene that its expression is significantly upregulated in PH mice on 15-HETE diet compared to chow diet. The levels of Scd1 products, palmitoleate and oleate, were significantly increased in the plasma of 15-HETE mice. Mechanistically, Scd1 product, Oleate was sufficient to increase expression of Scd1 and inflammatory marker IL-1β in PAEC, but not in PASMC. However, conditioned medium from Oleate-stimulated PAEC was able to increase IL-1β expression in PASMC and promote PASMC proliferation. Notably, EC-specific Scd1 Knock-Out mice did not develop PH on a 15-HETE diet, further highlighting the role of Scd1 in promoting EC dysfunction in PH.
Conclusion(s): Together, our data suggest that a 15-HETE-enriched diet induces upregulation of Scd1 in enterocytes, leading to the release of its products, oleate and palmitoleate, into the systemic circulation. These lipids promote PAEC dysfunction, which, in a paracrine manner, promote PASMC inflammation and proliferation.