PPARγ Activation Reduces Hypoxia-induced Endothelin-1 Expression through Upregulation of miR-98.

Abstract Endothelin-1 (ET-1) plays a critical role in endothelial dysfunction and contributes to the pathogenesis of pulmonary hypertension (PH). We hypothesized that PPARγ stimulates microRNAs that inhibit ET-1 and pulmonary artery endothelial cell (PAEC) proliferation. To clarify molecular mechanisms by which PPARγ regulates ET-1 expression in vitro and in vivo. In PAEC isolated from patients with pulmonary arterial hypertension, miR-98 expression was reduced, and ET-1 protein levels and proliferation were increased. Similarly, hypoxia reduced miR-98 and increased ET-1 levels and PAEC proliferation in vitro. In vivo, hypoxia reduced miR-98 expression and increased ET-1 and PCNA levels in mouse lung, derangements that were aggravated by treatment with the vascular endothelial growth factor receptor antagonist, Sugen5416. Reporter assays confirmed that miR-98 binds directly to the ET-1 3'-untranslated region. Compared to littermate control mice, miR-98 levels were reduced and ET-1 and PCNA expression were increased in lungs from endothelial-targeted PPARγ knockout mice, whereas miR-98 levels were increased and ET-1 and PCNA expression were reduced in lungs from endothelial-targeted PPARγ overexpression mice. Gain or loss of PPARγ function in PAEC in vitro confirmed that alterations in PPARγ were sufficient to regulate miR-98, ET-1, and PCNA expression. Finally PPARγ activation with rosiglitazone regimens that attenuated hypoxia-induced PH in vivo and human PAEC proliferation in vitro restored miR-98 levels. PPARγ regulates miR-98 to modulate ET-1 expression and PAEC proliferation. These results further clarify molecular mechanisms by which PPARγ participates in PH pathogenesis and therapy.