Abstract 10815: C-Terminal Src Kinase Inhibits Endothelial Fibrosis and is Upregulated in Early-Stage Experimental Pulmonary Arterial Hypertension

Abstract

Introduction: Advanced-stage pulmonary arterial hypertension (asPAH) is characterized by endothelial dysfunction and fibrotic remodeling of pulmonary arterioles that promotes irreversible right heart failure. Thus, identifying mechanisms that regulate vascular fibrosis in early PAH (esPAH) may have translational importance. Hypothesis: We hypothesized that profibrotic molecular pathways differentiate esPAH from asPAH. Methods: To test this hypothesis, male Sprague-Dawley rats were administered one dose of monocrotaline (60 mg/kg; day 0) to induce inflammatory PAH. Cardiac catheterization and pulmonary artery endothelial cell (PAEC) transcriptomic analyses were performed on days 15 and 21 for esPAH and asPAH, respectively. Results: The esPAH profile included: right ventricular-pulmonary arterial (RV-PA) uncoupling (1.13 ± 0.05 vs. 0.90 ± 0.06, RV end-systolic elastance/PA elastance, P=0.02, N=6) and increased indexed pulmonary vascular resistance (50 ± 8 vs. 213 ± 29 mmHg*min*g -1 *mL -1 , P<0.001, N=6) without substantial elevation in PA systolic pressure (25 ± 1.2 vs. 33 ± 2.7 mmHg, P=0.02, N=6). Network medicine identified upregulation of c-terminal src kinase (Csk) as a mediator of PAEC fibrosis in esPAH but not asPAH in silico . Pulmonary endothelial expression of Csk protein by immunofluorescence correlated with vascular collagen by picrosirius red stain (r=+0.87, P=0.006, N=4). To validate these findings in vitro , human PAECs (HPAEC) were treated with an inflammatory stimulus of lipopolysaccaride (0.03 mg/mL) + interferon-γ (50 ng/mL) + interleukin-1β (50 ng/mL), or vehicle control (V). Compared to V-control, inflammation increased Csk protein and mRNA expression by 2.3- and 2.0-fold, respectively (P<0.05, N=4). Inflammation also increased HPAEC hydroxyproline, an indicator of collagen abundance, by 3.1-fold (P=1.4x10 -4 , N=4) vs. V-treated cells. Overexpression of Csk by adenovirus transfection attenuated inflammation-mediated hydroxyproline accumulation by 84% (P=1.3x10 -5 , N=3). Conclusions: These data suggest that impaired Csk may underlie HPAEC fibrosis in esPAH, which, in turn, may have potential therapeutic implications for the prevention of fibrotic vascular remodeling and PAH progression.