Twist1 in Hypoxia-induced Pulmonary Hypertension through Transforming Growth Factor-β–Smad Signaling

Abstract

Pulmonary hypertension (PH) is a devastating pulmonary vascular disease characterized by aberrant muscularization of the normally nonmuscularized distal pulmonary arterioles. The expression of the transcription factor, Twist1, increases in the lungs of patients with pulmonary arterial hypertension. However, the mechanisms by which Twist1 controls the pathogenesis of PH remain unclear. It is becoming clear that endothelial-to-mesenchymal transition (EndMT) contributes to various vascular pathologies, including PH; Twist1 is known to mediate EndMT. In this report, we demonstrate that Twist1 overexpression increases transforming growth factor (TGF) β receptor2 (TGF-βR2) expression and Smad2 phosphorylation, and induces EndMT in cultured human pulmonary arterial endothelial (HPAE) cells, whereas a mutant construct of Twist1 at the serine 42 residue (Twist1S42A) fails to induce EndMT. We also implanted fibrin gel supplemented with HPAE cells on the mouse lung, and found that these HPAE cells form vascular structures and that Twist1-overexpressing HPAE cells undergo EndMT in the gel, whereas Twist1S42A-overexpressing cells do not. Furthermore, hypoxia-induced EndMT is inhibited in endothelial cells overexpressing Twist1S42A mutant construct in vitro. Hypoxia-induced accumulation of α-smooth muscle actin-positive cells in the pulmonary arterioles is attenuated in Tie2-specific Twist1 conditional knockout mice in vivo. These findings suggest that Twist1 serine 42 phosphorylation plays a key role in EndMT through TGF-β signaling and that modulation of Twist1 phosphorylation could be an effective strategy for managing PH.

Endothelial-to-Mesenchymal Transition in Pulmonary Hypertension

“…EndoMT was also observed in systemic sclerosis-associated PAH where cells expressing both endothelial and mesenchymal markers were found in 4% of the remodeled vessels [9]. Since then various studies have confirmed the occurrence of an ongoing EndoMT process in PAH with the overexpression of transcription factors Twist/ Snail/Slug [10][11][12].…”

“…TGF-β also promotes EndoMT through various Smad-independent pathways leading, for example, to the inactivation of GSK-3β, a repressor of Snail-and β-catenin-induced EndoMT or to the PI3K/AKT-mediated up-regulation of Twist/ Snail/Slug/ZEB expression through mTOR and NF-κB activation. Finally autocrine feedback loops appear in TGF-β-induced EndoMT since Twist overexpression in human pulmonary ECs also up-regulates TGF-β expression [11].…”

A Computational Model of the Endothelial to Mesenchymal Transition

“…According to the dynamic behavior of the model, the loss of any of the transcription factors SNAI2, TWIST1, ZEB1, and ZEB2 prevents mesenchymal cell differentiation. Experimentally, the loss of SNAI2 (Niessen et al, 2008), TWIST1 (Mammoto et al, 2018), or ZEB1 (Sanchez-Tillo et al, 2010 prevents EndMT. ZEB2 has many functions in addition to its role during EndMT, its loss causes severe neurodevelopmental defects and cardiovascular malformations (Epifanova et al, 2018), while its specific effect during EndMT still needs to be elucidated.…”

“…Nevertheless, we know that the activity of several molecules, including NRP1 (Oh et al, 2002;Matkar et al, 2016), SNAI1 (Sun et al, 2018), SNAI2 (Welch-Reardon et al, 2015),n WNT5b (Wang et al, 2017a), and WNT7a (Howe et al, 2003;Pahnke et al, 2016) induce both EC activation and EndMT. Furthermore, TWIST1 (Mammoto et al, 2018), ZEB1 (Sanchez-Tillo et al, 2010), and ZEB2 (DaSilva-Arnold et al, 2018) induce EndMT and are not known to be involved in EC activation during angiogenesis. Finally, the activity of FGF2 (Ichise et al, 2014;Yang et al, 2015), and VEGFA (Paruchuri et al, 2006) induce angiogenesis and inhibit full EndMT.…”

Twist1: A Double-Edged Sword in Kidney Diseases

“…Under hypoxic conditions, endothelial cells of pulmonary arterioles express α-SMA, a mesenchymal cell marker, whereas Twist1 deficiency in these cells attenuates α-SMA positive cell accumulation in vivo. In vitro studies demonstrate that Twist1 Ser-42 phosphorylation is responsible for endothelial to mesenchymal transition through TGFβ-Smad2 signaling [57]. Thus, Twist1 not only in epithelial but also in endothelial cells governs mesenchymal phenotypes in response to pathogenic stimuli.…”