Interleukin-6 Modulates the Expression of the Bone Morphogenic Protein Receptor Type II Through a Novel STAT3–microRNA Cluster 17/92 Pathway

Abstract

Abstract-Dysregulated expression of bone morphogenetic protein receptor type II (BMPR2) is a pathogenetic hallmark of pulmonary hypertension. Downregulation of BMPR2 protein but not mRNA has been observed in multiple animal models mimicking the disease, indicating a posttranscriptional mechanism of regulation. Because microRNAs (miRNAs) regulate gene expression mainly through inhibition of target gene translation, we hypothesized that miRNAs may play a role in the modulation of BMPR2. Performing a computational algorithm on the BMPR2 gene, several miRNAs encoded by the miRNA cluster 17/92 (miR-17/92) were retrieved as potential regulators. Ectopic overexpression of miR-17/92 resulted in a strong reduction of the BMPR2 protein, and a reporter gene system showed that BMPR2 is directly targeted by miR-17-5p and miR-20a. By stimulation experiments, we found that the miR-17/92 cluster is modulated by interleukin (IL)-6, a cytokine involved in the pathogenesis of pulmonary hypertension. Because IL-6 signaling is mainly mediated by STAT3 (signal transducer and activator of transcription 3), the expression of STAT3 was knocked down by small interfering RNA, which abolished the IL-6 -mediated expression of miR-17/92. Consistent with these data, we found a highly conserved STAT3-binding site in the promoter region of the miR-17/92 gene (C13orf25). Promoter studies confirmed that IL-6 enhances transcription of C13orf25 through this distinct region. Finally, we showed that persistent activation of STAT3 leads to repressed protein expression of BMPR2. Taken together, we describe here a novel STAT3-miR-17/92-BMPR2 pathway, thus providing a mechanistic explanation for the loss of BMPR2 in the development of pulmonary hypertension. Key Words: pulmonary hypertension Ⅲ BMPR2 Ⅲ miR-17/92 Ⅲ interleukin-6 Ⅲ STAT3 P ulmonary hypertension is a devastating condition defined by the sustained elevation of pulmonary vascular resistance that leads rapidly to right heart failure and death when left untreated. 1 The pathogenesis of pulmonary hypertension is characterized by vascular remodeling and vasoconstriction. 2 Many chemotactic and inflammatory factors have been associated with these vascular changes including interleukin (IL)-6 and transforming growth factor (TGF)␤. [3][4][5] In familial pulmonary arterial hypertension, germline mutations in the gene encoding the type II receptor of the bone morphogenetic protein (BMPR2) comprise a genetic hallmark of the disease. 6 BMPR2 is a surface protein receptor that belongs to the transforming growth factor (TGF)␤ family. Its expression on endothelial and vascular smooth muscle cells mediates binding of bone morphogenetic proteins (BMPs) that have been identified as inhibitors of vascular smooth muscle cell proliferation while inducing cell death. 7 Thus, it was suggested that the downregulation of BMPR2 might lead to significant alterations in these signaling cascades and, ultimately, to remodeling of the pulmonary vascular bed. 8 Of interest, alterations in the surface expression of BMPR2 ha...

Translational Advances in the Field of Pulmonary Hypertension.Translating MicroRNA Biology in Pulmonary Hypertension. It Will Take More Than “miR” Words

“…Not only was the miR-130/301 family identified as the top-ranked miRNA family, but also such network analyses outlined a model of downstream actions of these miRNAs to include two known proliferative pathways, a pathway influencing vasoconstriction, and a novel signaling mechanism controlling extracellular matrix deposition and remodeling. These findings were verified in vivo and in vitro (15,19,20,24,31), thus demonstrating the power of combining computational bioinformatics with experimental biology and affording distinct advantages as compared with traditional scientific approaches. Network gene analyses may be applied to the current challenges of understanding the collective actions of PH-specific miRNAs on overall disease manifestation rather than merely focusing on single actions of an miRNA in isolation.…”

“…For instance, the polycistronic miR-17-92 cluster was found to be down-regulated in vascular cells from patients with PAH. Overexpression of this miRNA cluster resulted in direct transcript binding of miR-17-5p and miR-20a (24) and consequent expression of BMPR2. Correspondingly, in vivo inhibition of several members of the cluster, using oligonucleotide inhibitors (i.e., antagomiRs) or targeted genetic deletion of the entire cluster, was shown to improve experimental PH (25)(26)(27).…”

MicroRNA-223 controls the expression of histone deacetylase 2: a novel axis in COPD

“…The mRNA levels, however, remained almost unchanged suggesting a miRNA-mediated inhibition of the translational process of the targeted transcript. Such a mechanistic interplay is frequently observed in the context of miRNA mediated gene regulation in human disease including pulmonary disorders [22]. Of note, when miR-223 was silenced using miRNA-inhibitors only minor effects could be observed on the expression levels of HDAC2.…”

The role of STAT3 in autophagy

“…For example, STAT3 upregulates MIR17HG (miR-17-92 cluster host gene [non-protein coding]) through a highly conserved STAT3 binding site in the promoter region, 52 and members of the MIR17HG cluster have been reported to target the autophagy-related genes ULK1, BECN1, and BCL2L11. [53][54][55] Several miRNAs that have been transcriptionally modulated by STAT3 and have been reported to target autophagy pathways are summarized in Table 2.…”