Abstract 19603: Disruption of βPDGF Receptor-Dependent PI3k and Plcγ Signaling Protects from Hypoxia-Induced Pulmonary Hypertension
Background: Vascular remodeling is critical during the pathogenesis of pulmonary hypertension (PH). Growth factors, such as platelet-derived growth factor (PDGF), appear to be involved in these processes. With pharmacological inhibitors, we demonstrated previously that phosphatidyl inositol-3 kinase (PI3K) and phospholipase Cγ (PLCγ) are the critical mediators of βPDGF receptor (βPDGFR)-dependent proliferation and migration in pulmonary arterial smooth muscle cells (PASMC). Whereas expression data and data with the tyrosine kinase inhibitor imatinib suggest a role for PDGF in PH, data from genetic models is lacking.
Methods and results: We utilized βPDGFR F3/F3 (“F3”) mice that were generated by introducing point mutations of the PI3K and PLCγ binding sites into the βPDGFR locus by gene targeting. We isolated PASMC from F3 and wild-type (WT) mice. Co-immunoprecipitation experiments after PDGF treatment showed that PI3K and PLCγ did not bind to the activated F3 receptor, whereas overall phosphorylation and binding of RasGap and SHP-2 were unaffected. In line with these observations, PDGF-mediated phosphorylation of Akt and Erk 1/2 was inhibited in F3-PASMC compared to WT. To address, if cellular responses were altered, we analyzed βPDGFR-dependent proliferation (as BrdU incorporation) and migration (modified Boyden chamber). These experiments revealed that these responses were essentially completely blocked in F3-PASMC compared to WT. To analyze the development and severity of PH in vivo, we exposed F3 and WT mice to hypoxia for 3 weeks. Following this treatment, right ventricular systolic pressure (RVSP) was measured by right heart catheterization, and right ventricular (RV) hypertrophy was assessed as RV weight/left ventricular + septal weight (RV/LV+S). These analyses revealed that RVSP and RV/LV+S were significantly reduced in F3 compared to WT mice.
Conclusions: These data show that disruption of βPDGFR-dependent PI3K and PLCγ signaling blocks PDGF-dependent proliferation and migration of PASMC in vitro and protects from the development of hypoxia-induced PH in vivo. Consequently, these data support a critical role of PDGF during the pathogenesis of PH.
- © 2012 by American Heart Association, Inc.