Abstract 21217: PTP1B is a Critical Mediator for Vascular Smooth Cell Proliferation in the Development of Pulmonary Hypertension in vivo and in vitro

Abstract

Background: Pulmonary hypertension (PH) is characterized by pulmonary vascular remodeling that leads to right ventricular failure and death. In PH, vascular remodeling is driven by hyper-proliferative and anti-apoptotic pulmonary arterial smooth muscle cells (PASMC). Protein Tyrosine Phosphatase 1B (PTP1B), is a negative regulator for apoptosis and proliferation of vascular smooth muscle cells through down-stream mediators such as BCL-2. While BCL-2 is increased in PH patients, the pathways for regulating BCL-2 are poorly understood. Therefore, our aim is to investigate if PTP1B has a role in PASMC proliferation and resistance to apoptosis in human PASMCs and in the angioproliferative Sugen/Hypoxia/Normoxia (SuHx) PH rat model. Method: Male Sprague-Dawley rats were treated with a single intraperitoneal dose of a vascular endothelial growth factor antagonist (SU5416, 20 mg/kg, n=4) and kept in hypoxia for 3 weeks followed by normoxia for 2 weeks. Saline treated controls were kept in normoxia for 5 weeks (n=4). RV systolic pressure (RVSP) was recorded by RV catheterization and hearts were isolated to assess RV hypertrophy (RV/LV + IVS). PTP1B and BCL-2 expression was determined using qPCR. Healthy hPASMCs were incubated with a PTP1B inhibitor (Ethyl-3,4-dephostatin) at IC50=0.58ug/ml for 24hrs and stained with Ki67 to assess for proliferation. Results: SuHx rats had severe PH, evident by elevated RVSP compared to control (88.97+/- 13.67 vs. 28.47+/- 2.22 mmHg, p<0.05). PH rats also showed reduced RV function and increased hypertrophy (0.7+/- 0.063 vs 0.274 +/-0.01 in control, p<0.05). PH lungs exhibited pulmonary vascular remodeling characterized by excessive growth of the PASMCs. PTP1B was decreased in PH lungs compared to controls (0.158+/-0.0647 vs 1+/-0.06, P<0.05). As expected, BCL-2 expression was significantly increased in PH compared to control (2.01+/-0.162 vs 1 +/-0.1, P<0.01). Inhibition of PTP1B in cultured hPASMCs increased proliferation by ~2 fold as assessed by Ki67 positive cells. Conclusion: Severe Angioproliferative PH in rats is associated with a downregulation of PTP1B and increased expression of BCL-2. Additionally, PTP1B inhibition resulted in hPASMC proliferation, suggesting a role for PTP1B in the pathogenesis of PH.