Abstract 494: Role of Slug / PIP Axis in Pulmonary Hypertension Secondary to Pulmonary Fibrosis

Abstract

Pulmonary hypertension (PH) secondary to pulmonary fibrosis (PF-PH) is the second most common cause of PH. While never studied in detail, pathology reports suggest that vascular remodeling (VR) differs between PF and PF-PH. In PF, VR is mainly limited to fibrotic areas, whereas in PF-PH, it also exist in non-fibrotic areas. These histological differences suggest potential molecular differences. To better understand this mechanism, we investigated the expression of the transcription factor Slug which is known to play a role in PH and PF. Using explanted rat (n=7/group) and human (n=7-14/group) lungs, we compared lung fibrosis, VR and Slug expression between non-fibrotic and fibrotic areas in PF and PF-PH. Online microarray data (GSE24988) were used to find the targets of Slug that are implicated in VR. A new animal model recapitulating our findings in patients was used to test the therapeutic potential of Slug inhibition (n=10/group). This model is based on intra-tracheal instillation of bleomycin (2.5mg/Kg) at day 0 and 2weeks later, an injection of monocrotaline (60mg/kg). PH was assessed by right ventricular systolic pressure (RVSP). P<0.05 are considered significant. In both PF and PF-PH patients, fibrotic areas (PF29±4; PF-PH37±3) exhibit significantly increased VR when compared to non-fibrotic areas of the lung (PF 22±1; PF-PH 31±6). PF-PH patients have increased pulmonary vascular thickening in both areas vs PF patients. This is concomitant with an increased number of Ki67+ vascular cells in PF-PH (12±2%) vs PF (8±1%) as well as an upregulation of Slug in PF-PH patients (2.3±0.5) vs PF (1±0.1). Co-immunolabeling with CD68 demonstrate that macrophages are the main cell type responsible for Slug up-regulation in PF-PH. Human microarray data reveal an up-regulation of the Prolactin-induced protein (PIP) in PF-PH vs PF (9±3 vs 1±0.4). PIP is an extracellular transcriptional target of Slug, known to promote cell proliferation. In-vitro, PIP significantly increases pulmonary arterial smooth muscle cell proliferation in a dose dependent manner. Finally, Slug inhibition decreases RVSP (47±3 vs 62±3mmHg) in an animal model of PF-PH. There are histological differences between PF-PH and PF lungs that are at least in part mediated by a Slug/PIP axis leading to VR.