Reduced miR-204 expression facilitates the excessive proliferation and apoptosis resistance of pulmonary artery smooth muscle cells characteristic of human pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is characterized by enhanced proliferation and reduced apoptosis of pulmonary artery smooth muscle cells (PASMCs). Because microRNAs have been recently implicated in the regulation of cell proliferation and apoptosis, we hypothesized that these regulatory molecules might be implicated in the etiology of PAH. In this study, we show that miR-204 expression in PASMCs is down-regulated in both human and rodent PAH. miR-204 down-regulation correlates with PAH severity and accounts for the proliferative and antiapoptotic phenotypes of PAH-PASMCs. STAT3 activation suppresses miR-204 expression, and miR-204 directly targets SHP2 expression, thereby SHP2 up-regulation, by miR-204 down-regulation, activates the Src kinase and nuclear factor of activated T cells (NFAT). STAT3 also directly induces NFATc2 expression. NFAT and SHP2 were needed to sustain PAH-PASMC proliferation and resistance to apoptosis. Finally, delivery of synthetic miR-204 to the lungs of animals with PAH significantly reduced disease severity. This study uncovers a new regulatory pathway involving miR-204 that is critical to the etiology of PAH and indicates that reestablishing miR-204 expression should be explored as a potential new therapy for this disease. role of miR-204 in the etiology of PAH. Interestingly, using in silico and microarray gene expression analyses, we observed that among the 461 predicted targets of miR-204 (TargetScan 5.1), only 165 were increased by artificial miR-204 inhibition in control human PASMCs (n = 2 patients; Fig. S1 C). In accordance with the pro-proliferative and antiapoptotic phenotypes seen in PAH, several Src-STAT3-and NFAT-related genes were identified (Fig. S1 C). miR-204 expression is decreased in human PAH and correlates with PAH severityTo investigate the expression pattern of miR-204 in normal and pulmonary hypertensive lungs, we examined miR-204 expression levels in (a) lung biopsies from 8 individuals with nonfamilial PAH compared with biopsies from 8 individuals without pulmonary hypertension, (b) lungs from 6 mice with hypoxia-induced pulmonary hypertension compared with 5 control littermates, and (c) lungs from 5 rats with monocrotaline (MCT)-induced pulmonary hypertension compared with 10 control littermates ( Fig. 1 A). We found decreased levels of miR-204 in human and rodent pulmonary hypertensive lung tissues compared with normotensive lung samples. To characterize whether down-regulated miR-204 levels were specific to the lung in rats with pulmonary hypertension, we compared organ-specific levels of miR-204 between normal and pulmonary hypertensive rats (Fig. 1 B). Even if we were able to detect minimal amounts of miR-204 in most organs, miR-204 levels were only down-regulated in the lung and PAs but not in the aorta, liver, heart, and kidney in rats 3 wk after MCT injection (pulmonary hypertensive rats) compared with non-pulmonary hypertensive rats (Fig. 1 B).To test whether miR-204 down-regulation correlated with disease progression, we studied humans, mice, a...

Like cancer, pulmonary arterial hypertension (PAH) is characterised by a proproliferative and anti-apoptotic phenotype. In PAH, pulmonary artery smooth muscle cell (PASMC) proliferation is enhanced and apoptosis suppressed. The sustainability of this phenotype requires the activation of pro-survival transcription factors, such as signal transducer and activator of transcription (STAT)3 and nuclear factor of activated T-cells (NFAT). There are no drugs currently available that are able to efficiently and safely inhibit this axis. We hypothesised that plumbagin (PLB), a natural organic compound known to block STAT3 in cancer cells, would reverse experimental pulmonary hypertension.Using human PAH-PASMC, we demonstrated in vitro that PLB inhibits the activation of the STAT3/NFAT axis, increasing the voltage-gated K + current bone morphogenetic protein receptor type II (BMPR2), and decreasing intracellular Ca 2+ contentration ([Ca 2+ ] i ), rho-associated coiledcoil containing protein kinase (ROCK)1 and interleukin (IL)-6, contributing to the inhibition of PAH-PASMC proliferation and resistance to apoptosis (proliferating cell nuclear antigen (PCNA), TUNEL, Ki67 and anexine V). In vivo, PLB oral administration decreases distal pulmonary artery remodelling, mean pulmonary artery pressure and right ventricular hypertrophy without affecting systemic circulation in both monocrotaline-and sugen/chronic hypoxia-induced PAH in rats.This study demonstrates that the STAT3/NFAT axis can be therapeutically targeted by PLB in human PAH-PASMC and experimental PAH rat models. Thus, PLB could be considered a specific and attractive future therapeutic strategy for PAH.