Inhibitory Antibodies against Activin A and TGF-β Reduce Self-Supported, but Not Soluble Factors-Induced Growth of Human Pulmonary Arterial Vascular Smooth Muscle Cells in Pulmonary Arterial Hypertension.

Tatiana Kudryashova,Evelyn Okorie,Elena Goncharova,Emily Cronin,Dmitry Goncharov,Yuanjun Shen,Andressa Pena

doi:10.3390/ijms19102957

Abstract

Increased growth and proliferation of distal pulmonary artery vascular smooth muscle cells (PAVSMC) is an important pathological component of pulmonary arterial hypertension (PAH). Transforming Growth Factor-β (TGF-β) superfamily plays a critical role in PAH, but relative impacts of self-secreted Activin A, Gremlin1, and TGF-β on PAH PAVSMC growth and proliferation are not studied. Here we report that hyper-proliferative human PAH PAVSMC have elevated secretion of TGF-β1 and, to a lesser extent, Activin A, but not Gremlin 1, and significantly reduced Ser465/467-Smad2 and Ser423/425-Smad3 phosphorylation compared to controls. Media, conditioned by PAH PAVSMC, markedly increased Ser465/467-Smad2, Ser423/425-Smad3, and Ser463/465-Smad1/5 phosphorylation, up-regulated Akt, ERK1/2, and p38 MAPK, and induced significant proliferation of non-diseased PAVSMC. Inhibitory anti-Activin A antibody reduced PAH PAVSMC growth without affecting canonical (Smads) or non-canonical (Akt, ERK1/2, p38 MAPK) effectors. Inhibitory anti-TGF-β antibody significantly reduced P-Smad3, P-ERK1/2 and proliferation of PAH PAVSMC, while anti-Gremlin 1 had no anti-proliferative effect. PDGF-BB diminished inhibitory effects of anti-Activin A and anti-TGF-β antibodies. None of the antibodies affected growth and proliferation of non-diseased PAVSMC induced by PAH PAVSMC-secreted factors. Together, these data demonstrate that human PAH PAVSMC have secretory, proliferative phenotype that could be targeted by anti-Activin A and anti-TGF-β antibodies; potential cross-talk with PDGF-BB should be considered while developing therapeutic interventions.

Highlights

Pulmonary arterial hypertension (PAH) is a progressive and rapidly fatal disease with high mortality rates and no curative options [1,2,3,4]
Supporting previously published studies [41], we found that human PAH pulmonary arterial vascular smooth muscle cells (PAVSMC)
That human PAH PAVSMC, while secreting high amounts of active TGF-β1 and/or Activin A, had reduced activatory phosphorylation of both, Ser465/467-Smad2 and Ser423/425-Smad3

Summary

Introduction

Pulmonary arterial hypertension (PAH) is a progressive and rapidly fatal disease with high mortality rates and no curative options [1,2,3,4]. Most patients with PAH are unresponsive to traditional vasodilators, and available therapies fail to reverse established pulmonary vascular remodeling or prevent disease progression, making development of effective remodeling-focused therapeutics an area of unmet important need. Most ligands of the TGF-β superfamily, except for inhibin-α, bind to type I receptors (the centerpiece) and type II receptors (the activator), which initiate Smad activation [10]. Dependent on ligand-receptor interactions, the phosphorylation of the regulated Smad (R-Smad) can transduce either TGF-β-like signals, such as the activation of Smad 2 and 3, or BMP-like signals, such as the activation of Smad1/5 [9,10]. Embryonic studies have shown that there are several diffusible ligand-binding proteins that prevent TGF-β ligands from accessing their respective receptors, such as latency-associated protein (LAP) for TGF-β, follistatin for Activin A, and Gremlin for BMPs [10]

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