Abstract 321: Protein Tyrosine Phosphatase 1B: a Novel Regulator of Proliferation and Apoptosis in the Development of Pulmonary Arterial Hypertension

Background: Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling that leads to an increase in pulmonary arterial pressure resulting in right ventricle failure and death. PAH is driven by pulmonary artery smooth muscle cell (PASMC) proliferation and resistance to apoptosis. Protein Tyrosine Phosphatase 1B (PTP1B), a negative regulator for platelet-derived growth factor (PDGF) and BCL-2, has recently been implicated in PAH in humans. While PDGF and BCL-2 are increased in PAH patients, the pathway for regulating BCL-2 and PDGF is poorly understood. We aim to investigate if PTP1B has a role in proliferation and resistance to apoptosis in PAH in human PACMCs and in the Sugen/Hypoxia/Normoxia (Su/Hx/Nx) PH rat model. Method: Adult male Sprague-Dawley rats were treated with single intraperitoneal dose of SU5416 (20 mg/kg) and kept in Hx for 3 weeks followed by Nx for 2 weeks. Saline treated rats kept in Nx for 5 weeks served as control (n=4/group). RV catheterization was performed terminally for recording RV systolic pressure (RVSP). RV, LV, and interventricular septum (IVS) were isolated for Fulton index (FI, RV/IVS+LV). We analyzed gene expression in lungs via qPCR. Healthy hPASMCs were incubated with a PTP1B inhibitor (Ethyl-3,4-dephostatin) at IC50=0.58ug/ml for 24hrs under Nx conditions and cells were stained with Ki67 to assess proliferation. Results: Su/Hx/Nx rats had severe PH evidenced by a significantly elevated RVSP compared to control (88.97+/- 13.67 vs 28.47+/- 2.22 mmHg, p<0.05). PH rats also showed severely reduced RV function and increased RV hypertrophy (FI= 0.7+/- 0.063 vs 0.274 +/-0.01, p<0.05). PH lungs exhibited severe pulmonary vascular remodeling with excessive growth of the PASMCs. PTP1B was significantly decreased in PH lungs compared to controls (0.158+/-0.0647 vs 1+/-0.06, P<0.05). BCL-2 expression was significantly increased in PAH 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 (n=3). Conclusion: Severe angioproliferative PH in rats is associated with a downregulation of PTP1B and increased expression of BCL-2 and PASMC proliferation.