Peroxisome Proliferator-Activated Receptor gamma and microRNA 98 in Hypoxia-Induced Endothelin-1 Signaling

Endothelin-1 (ET-1) plays a critical role in endothelial dysfunction and contributes to the pathogenesis of pulmonary hypertension (PH). We hypothesized that peroxisome proliferator-activated receptor gamma (PPAR gamma) stimulates microRNAs that inhibit ET-1 and pulmonary artery endothelial cell (PAEC) proliferation. The objective of this study was to clarify molecular mechanisms by which PPARg regulates ET-1 expression in vitro and in vivo. In PAECs isolated from patients with pulmonary arterial hypertension, microRNA (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 proliferating cell nuclear antigen (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 39-untranslated region. Compared with littermate control mice, miR-98 levels were reduced and ET-1 and PCNA expression were increased in lungs from endothelial-targeted PPARg knockoutmice, where as miR-98 levels were increased and ET-1 and PCNA expression was reduced in lungs from endothelial-targeted PPAR gamma-over expression mice. Gain or loss of PPARg function in PAECs in vitro confirmed that alterations in PPARg were sufficient to regulate miR-98, ET-1, and PCNA expression. Finally, PPARg activation with rosiglitazone regimens that attenuated hypoxia-induced PH in vivo and human PAEC proliferation in vitro restored miR-98 levels. The results of this study show that PPARg regulates miR-98 to modulate ET-1 expression and PAEC proliferation. These results further clarify molecular mechanisms by which PPARg participates in PH pathogenesis and therapy.