HIPPO-Integrin-linked Kinase Cross-Talk Controls Self-Sustaining Proliferation and Survival in Pulmonary Hypertension.
BACKGROUND
Enhanced proliferation and impaired apoptosis of pulmonary arterial vascular smooth muscle cells (PAVSMCs) are key pathophysiologic components of pulmonary vascular remodeling in pulmonary arterial hypertension (PAH).


OBJECTIVE
To determine the role and therapeutic relevance of HIPPO signaling in PAVSMC proliferation/apoptosis imbalance in PAH.


METHODS
Primary distal PAVSMCs, lung tissue sections from unused donor (control) and idiopathic PAH lungs, and rat and mouse models of SU5416/hypoxia-induced pulmonary hypertension (PH) were used. Immunohistochemical, immunocytochemical, and immunoblot analyses and transfection, infection, DNA synthesis, apoptosis, migration, cell count, and protein activity assays were performed in this study.


RESULTS
Immunohistochemical and immunoblot analyses demonstrated that the HIPPO central component large tumor suppressor 1 (LATS1) is inactivated in small remodeled pulmonary arteries (PAs) and distal PAVSMCs in idiopathic PAH. Molecular- and pharmacology-based analyses revealed that LATS1 inactivation and consequent up-regulation of its reciprocal effector Yes-associated protein (Yap) were required for activation of mammalian target of rapamycin (mTOR)-Akt, accumulation of HIF1α, Notch3 intracellular domain and β-catenin, deficiency of proapoptotic Bim, increased proliferation, and survival of human PAH PAVSMCs. LATS1 inactivation and up-regulation of Yap increased production and secretion of fibronectin that up-regulated integrin-linked kinase 1 (ILK1). ILK1 supported LATS1 inactivation, and its inhibition reactivated LATS1, down-regulated Yap, suppressed proliferation, and promoted apoptosis in PAH, but not control PAVSMCs. PAVSM in small remodeled PAs from rats and mice with SU5416/hypoxia-induced PH showed down-regulation of LATS1 and overexpression of ILK1. Treatment of mice with selective ILK inhibitor Cpd22 at Days 22-35 of SU5416/hypoxia exposure restored LATS1 signaling and reduced established pulmonary vascular remodeling and PH.


CONCLUSIONS
These data report inactivation of HIPPO/LATS1, self-supported via Yap-fibronectin-ILK1 signaling loop, as a novel mechanism of self-sustaining proliferation and apoptosis resistance of PAVSMCs in PAH and suggest a new potential target for therapeutic intervention.
1 Heart, Lung, Blood and Vascular Medicine Institute.
Tatiana V
http://orcid.org/0000-0002-2843-5554
TV
Kudryashova
1 Heart, Lung, Blood and Vascular Medicine Institute.
Dmitry A
DA
Goncharov
1 Heart, Lung, Blood and Vascular Medicine Institute.
Andressa
A
Pena
2 Department of Medicine, and.
Neil
N
Kelly
1 Heart, Lung, Blood and Vascular Medicine Institute.
Rebecca
R
Vanderpool
1 Heart, Lung, Blood and Vascular Medicine Institute.
Jeff
J
Baust
1 Heart, Lung, Blood and Vascular Medicine Institute.
Ahasanul
A
Kobir
3 Department of Surgery and Immunology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
William
W
Shufesky
1 Heart, Lung, Blood and Vascular Medicine Institute.|2 Department of Medicine, and.
Ana L
AL
Mora
3 Department of Surgery and Immunology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
Adrian E
AE
Morelli
2 Department of Medicine, and.
Jing
J
Zhao
4 Department of Pathology and Laboratory Medicine.|5 Pulmonary Vascular Disease Program.
Kaori
K
Ihida-Stansbury
1 Heart, Lung, Blood and Vascular Medicine Institute.|2 Department of Medicine, and.
Baojun
B
Chang
5 Pulmonary Vascular Disease Program.|6 Department of Medicine, and.
Horace
H
DeLisser
7 Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Denver, Aurora, Colorado; and.
Rubin M
RM
Tuder
5 Pulmonary Vascular Disease Program.|8 Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania.
Steven M
SM
Kawut
9 Department of Cardiology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
Herman H W
HH
Silljé
2 Department of Medicine, and.
Steven
S
Shapiro
1 Heart, Lung, Blood and Vascular Medicine Institute.|2 Department of Medicine, and.
Yutong
Y
Zhao
1 Heart, Lung, Blood and Vascular Medicine Institute.|2 Department of Medicine, and.
Elena A
http://orcid.org/0000-0001-7118-6752
EA
Goncharova
HIPPO/LATS1; ILK; PAH; proliferation/apoptosis imbalance; vascular smooth muscle