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Pharmacological inhibition of G9a ameliorates pulmonary vascular remodeling in PAH

ABSTRACT: Background:Pulmonary arterial hypertension (PAH) is a severe condition characterized by progressive vascular remodeling of small pulmonary arteries (PAs) causing sustained elevation of PA pressure, right ventricular failure and death. Similar to cancer cells, PA smooth muscle cells (PASMCs), which play a key role in pulmonary vascular remodeling, have adopted multiple mechanisms to sustain their survival and proliferation in the presence of stress. The histone methyltransferase G9a has been shown to exert oncogenic effects and to serve as a buffer against an exaggerated transcriptional response. Therefore, we hypothesized that G9a up-regulation in PAH plays a pivotal role in pulmonary vascular remodeling by maintaining the abnormal phenotype of PAH-PASMCs. Methods: G9alevels were measured in PAs and isolated PASMCs of PAH patients and animal models. Selective G9a pharmacological inhibitors were used in human PAH-PASMCs and in rodent PAH models (i.e.Fawn-Hooded rats and Sugen/Hypoxia-exposed mice). Results: We present evidence of increased expression of G9a in PASMCs from PAH patients as well as in remodeled PAs from animal models. We found that pharmacological inhibition of G9a activity using BIX01294 and UNC0642significantly reduces the prosurvival and proproliferative potentials of cultured PAH-PASMCs. Using RNA sequencing, further exploration revealed that G9a promotes extracellular matrix production and affords protection against the negative effects of an overactive stress response. Finally, we found that therapeutic treatment with BIX01294 reduced pulmonary vascular remodeling and lowered mean PA pressure in Fawn-Hooded rats. Treatment of Sugen/hypoxia-challenged mice with BIX01294 also improved pulmonary hemodynamics and right ventricular function. Conclusions:These findings suggest that G9a inhibition may represent a new therapeutic approach in PAH.

ORGANISM(S): Homo sapiens

PROVIDER: GSE200821 | GEO | 2023/01/20

REPOSITORIES: GEO

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Project description:Pulmonary arterial hypertension (PAH) is a progressive disorder leading to occlusive vascular remodeling. Current PAH therapies improve quality of life but do not reverse structural abnormalities in the pulmonary vasculature. Here, we used a high-throughput drug screen combined with in silico analyses of existing transcriptomic datasets to identify a promising lead compound to reverse PAH. Induced pluripotent stem cell-derived endothelial cells (iPSC-EC) generated from six patients with PAH were exposed to 4,500 compounds and assayed for improved cell survival after serum withdrawal using a chemiluminescent caspase assay. Subsequent validation of caspase activity and improved angiogenesis combined with in silico analyses using the Gene Expression Omnibus (GEO ) and Library of Integrated Network-Based Cellular Signatures (LINCS) databases revealed that the lead compound AG1296 was positively associated with an anti-PAH gene signature. AG1296 increased abundance of bone morphogenetic protein receptors (BMPR2 and Ia), downstream signaling and gene expression, and suppressed PAH smooth muscle cell proliferation. AG1296 induced regression of pulmonary arterial (PA) neointimal lesions in lung organ culture and PA occlusive changes in the Sugen/hypoxia rat model and reduced right ventricular systolic pressure. Moreover, AG1296 improved vascular function and BMPR2 signaling and showed better correlation with the anti-PAH gene signature than other tyrosine kinase inhibitors (TKIs) such as imatinib. Specifically, AG1296 upregulated the transcription factors and small mothers against decapentaplegic (SMAD)1/5 co-activators, cAMP-response element binding protein (CREB)3 and CREB5: CREB3 induced inhibitor of DNA binding 1 (ID1) and downstream genes that improved vascular function. Thus, drug discovery for PAH can be accelerated by combining a phenotypic screen using patient-specific iPSC-derived vascular cells with in silico analyses of publicly available datasets.