Endothelial Autocrine Signaling through CXCL12/CXCR4/FoxM1 Axis Contributes to Severe Pulmonary Arterial Hypertension.

Dan Yi,Maggie M Zhu,Zhiyu Dai,Qi Liao,You-Yang Zhao,Bin Liu,Ting Wang

doi:10.3390/ijms22063182

Abstract

Endothelial autocrine signaling is essential to maintain vascular homeostasis. There is limited information about the role of endothelial autocrine signaling in regulating severe pulmonary vascular remodeling during the onset of pulmonary arterial hypertension (PAH). In this study, we employed the first severe pulmonary hypertension (PH) mouse model, Egln1Tie2Cre (Tie2Cre-mediated disruption of Egln1) mice, to identify the novel autocrine signaling mediating the pulmonary vascular endothelial cell (PVEC) proliferation and the pathogenesis of PAH. PVECs isolated from Egln1Tie2Cre lung expressed upregulation of many growth factors or angiocrine factors such as CXCL12, and exhibited pro-proliferative phenotype coincident with the upregulation of proliferation-specific transcriptional factor FoxM1. Treatment of CXCL12 on PVECs increased FoxM1 expression, which was blocked by CXCL12 receptor CXCR4 antagonist AMD3100 in cultured human PVECs. The endothelial specific deletion of Cxcl12 (Egln1/Cxcl12Tie2Cre) or AMD3100 treatment in Egln1Tie2Cre mice downregulated FoxM1 expression in vivo. We then generated and characterized a novel mouse model with endothelial specific FoxM1 deletion in Egln1Tie2Cre mice (Egln1/Foxm1Tie2Cre), and found that endothelial FoxM1 deletion reduced pulmonary vascular remodeling and right ventricular systolic pressure. Together, our study identified a novel mechanism of endothelial autocrine signaling in regulating PVEC proliferation and pulmonary vascular remodeling in PAH.

Highlights

Pulmonary arterial hypertension (PAH) is characterized by a progressive increase of vascular resistance and obstructive vascular remodeling affecting pulmonary arterioles, eventually leading to right heart failure and death [1,2]
Our study identified the intriguing signaling of the endothelial autocrine pathway via the CXCL12/CXCR4/forkhead box M1 (FoxM1) axis, which mediates endothelial proliferation in the pathogenesis of PAH
To further understand the role of endothelial hyperproliferation in the pathogenesis of PAH, we confirmed that pulmonary vascular endothelial cells (PVECs) were pro-proliferative as evidenced by increased Ki67+ /CD31+ cells in the pulmonary vascular bed in Egln1Tie2Cre mice (Figure 1A)

Summary

Introduction

Pulmonary arterial hypertension (PAH) is characterized by a progressive increase of vascular resistance and obstructive vascular remodeling affecting pulmonary arterioles, eventually leading to right heart failure and death [1,2]. Therapies that attenuate PVEC proliferation may provide benefit to PAH patients Both autocrine and paracrine signaling pathways are important to maintain vascular homeostasis and contribute to pathological angiogenesis [6]. PVECs from PAH patients exhibit increased production of growth factors, such as FGF2, IL-6, ET-1, TGF-beta, etc. These factors promote PVECs/smooth muscle cells (SMCs)/fibroblast proliferation and survival, stimulate SMC vasoconstriction, and even recruit leukocytes [6]. Our previous study showed that FoxM1 is activated for endothelial regeneration after inflammatory lung injury [11,12], which often serves as a trigger of PAH development [13]. Our study identified the intriguing signaling of the endothelial autocrine pathway via the CXCL12/CXCR4/FoxM1 axis, which mediates endothelial proliferation in the pathogenesis of PAH

Results

Discussion

Human Samples

Endothelial Cells Isolation and RNA Sequencing Analysis

Immunofluorescent Staining and Histological Assessment

Western Blot Analysis