Endothelial Inflammation, Src Kinase Dysregulation, and Fibrosis in Early Pulmonary Arterial Hypertension

PROJECT SUMMARY/ABSTRACT In pulmonary arterial hypertension (PAH) inflammation and endothelial dysfunction promote fibroproliferative pulmonary arterial remodeling, right ventricular failure (RV), and early death despite modern PAH therapies. Patients with mild pulmonary hypertension (PH) have increased risk for functional impairment, disease progression, and death, which emphasizes an unmet clinical need to identify strategies to target pulmonary vascular remodeling at an earlier clinical stage, especially for patients such as those with inflammatory connective tissue diseases (CTD), who are at higher risk for poor outcome compared to other PAH populations. However, the molecular mechanisms regulating fibroproliferative pulmonary vasculopathy in early PAH are not known, as preclinical investigation relies on the use of end-stage lung tissue and cells. Using network medicine analysis, we identify C-terminal src kinase (Csk), a CTD-associated inhibition of the oncoprotein Src, as a mediator of endothelial cell dysfunction and fibrosis in an inflammatory model of early PAH. To study Csk in relation to endothelial dysfunction, we developed a model of endothelial inflammation which induces collagen accumulation, pro-fibrotic Src activation, and endotypes observed in PAH human pulmonary artery endothelial cells (HPAECs). Inflammation also upregulated collagen 22 (Col22A1), a fibril-associated collagen linked to CTD risk and malignancy, which we show is upregulated in human PAH and in early inflammatory PAH in vivo, an event that is Src-dependent in vitro. We observed that inflammation induced these phenotypes despite an overall upregulation of Csk expression, which raised the possibility that Csk may become dysfunctional through a deleterious post-translational modification. Indeed, in HPAECs, we identify failure of Csk to inhibit Src in the setting of inflammation. The central goal of this proposal is to identify the molecular mechanism regulating Csk dysfunction and the functional consequences of this mechanism for pulmonary vascular Col22A1 in early PAH. We propose the following specific aims: 1) Test the hypothesis that inflammation promotes Csk dysfunction and Src activation in HPAECs and 2) Define the pulmonary vascular phenotype of Csk-dependent Col22A1. Understanding Csk-Src dependent Col22A1 vasculopathy may identify strategies to target the inception of pulmonary vascular remodeling, which may have implications for PAH prevention in high risk CTD patients.