BMPRII deficiency impairs apoptosis via the BMPRII-ALK1-BclX-mediated pathway in pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a devastating cardiovascular disorder characterized by the remodelling of pre-capillary pulmonary arteries. The vascular remodelling observed in PAH patients results from excessive proliferation and apoptosis resistance of pulmonary arterial smooth muscle cells (PASMCs) and pulmonary arterial endothelial cells (PAECs). We have previously demonstrated that mutations in the type II receptor for bone morphogenetic protein (BMPRII) underlie the majority of the familial and inherited forms of the disease. We have further demonstrated that BMPRII deficiency promotes excessive proliferation and attenuates apoptosis in PASMCs, but the underlying mechanisms remain unclear. The major objective of this study is to investigate how BMPRII deficiency impairs apoptosis in PAH. Using multidisciplinary approaches, we demonstrate that deficiency in the expression of BMPRII impairs apoptosis by modulating the alternative splicing of the apoptotic regulator, B-cell lymphoma X (Bcl-x) transcripts: a finding observed in circulating leukocytes and lungs of PAH subjects, hypoxia-induced PAH rat lungs as well as in PASMCs and PAECs. BMPRII deficiency elicits cell specific effects: promoting the expression of Bcl-xL transcripts in PASMCs while inhibiting it in ECs, thus exerting differential apoptotic effects in these cells. The pro-survival effect of BMPRII receptor is mediated through the activin receptor-like kinase 1 (ALK1) but not the ALK3 receptor. Finally, we show that BMPRII interacts with the ALK1 receptor and pathogenic mutations in the BMPR2 gene abolish this interaction. Taken together, dysfunctional BMPRII responsiveness impairs apoptosis via the BMPRII-ALK1-Bcl-xL pathway in PAH. We suggest Bcl-xL as a potential biomarker and druggable target.

BMPR-II deficiency elicits pro-proliferative and anti-apoptotic responses through the activation of TGFß-TAK1-MAPK pathways in PAH.

Pulmonary arterial hypertension (PAH) is a cardiovascular disorder associated with enhanced proliferation and suppressed apoptosis of pulmonary arterial smooth muscle cells (PASMCs). Heterozygous mutations in the type II receptor for bone morphogenetic protein (BMPR2) underlie the majority of the inherited and familial forms of PAH. The transforming growth factor ß (TGFß) pathway is activated in both human and experimental models of PAH. However, how these factors exert pro-proliferative and anti-apoptotic responses in PAH remains unclear. Using mouse primary PASMCs derived from knock-in mice, we demonstrated that BMPR-II dysfunction promotes the activation of small mothers against decapentaplegia-independent mitogen-activated protein kinase (MAPK) pathways via TGFß-associated kinase 1 (TAK1), resulting in a pro-proliferative and anti-apoptotic response. Inhibition of the TAK1-MAPK axis rescues abnormal proliferation and apoptosis in these cells. In both hypoxia and monocrotaline-induced PAH rat models, which display reduced levels of bmpr2 transcripts, this study further indicates that the TGFß-MAPK axis is activated in lungs following elevation of both expression and phosphorylation of the TAK1 protein. In ex vivo cell-based assays, TAK1 inhibits BMP-responsive reporter activity and interacts with BMPR-II receptor. In the presence of pathogenic BMPR2 mutations observed in PAH patients, this interaction is greatly reduced. Taken together, these data suggest dysfunctional BMPR-II responsiveness intensifies TGFß-TAK1-MAPK signalling and thus alters the ratio of apoptosis to proliferation. This axis may be a potential therapeutic target in PAH.

Inhibition of overactive transforming growth factor-ß signaling by prostacyclin analogs in pulmonary arterial hypertension.

The heterozygous loss of function mutations in the Type II bone morphogenetic protein receptor (BMPR-II), a member of the transforming growth factor (TGF-ß) receptor family, underlies the majority of familial cases of pulmonary arterial hypertension (PAH). The TGF-ß1 pathway is activated in PAH, and inhibitors of TGF-ß1 signaling prevent the development and progression of PAH in experimental models. However, the effects of currently used therapies on the TGF-ß pathway remain unknown. Prostacyclin analogs comprise the first line of treatment for clinical PAH. We hypothesized that these agents effectively decrease the activity of the TGF-ß1 pathway. Beraprost sodium (BPS), a prostacyclin analog, selectively inhibits proliferation in a dose-dependent manner in murine primary pulmonary arterial smooth muscle cells (PASMCs) harboring a pathogenic BMPR2 nonsense mutation in both the presence and absence of TGF-ß1 stimulation. Our study demonstrates that this agent inhibits TGF-ß1-induced SMAD-dependent and SMAD-independent signaling via a protein kinase A-dependent pathway by reducing the phosphorylation of SMADs 2 and 3 and p38 mitogen-activated protein kinase proteins. Finally, in a monocrotaline-induced rat model of PAH, which is associated with increased TGF-ß signaling, this study confirms that treprostinil, a stable prostacyclin analog, inhibits the TGF-ß pathway by reducing SMAD3 phosphorylation. Taken together, these data suggest that prostacyclin analogs inhibit dysregulated TGF-ß signaling in vitro and in vivo, and reduce BMPR-II-mediated proliferation defects in mutant mice PASMCs.

Development and Optimisation of Inhalable EGCG Nano-Liposomes as a Potential Treatment for Pulmonary Arterial Hypertension by Implementation of the Design of Experiments Approach.

Epigallocatechin gallate (EGCG), the main ingredient in green tea, holds promise as a potential treatment for pulmonary arterial hypertension (PAH). However, EGCG has many drawbacks, including stability issues, low bioavailability, and a short half-life. Therefore, the purpose of this research was to develop and optimize an inhalable EGCG nano-liposome formulation aiming to overcome EGCG's drawbacks by applying a design of experiments strategy. The aerodynamic behaviour of the optimum formulation was determined using the next-generation impactor (NGI), and its effects on the TGF-ß pathway were determined using a cell-based reporter assay. The newly formulated inhalable EGCG liposome had an average liposome size of 105 nm, a polydispersity index (PDI) of 0.18, a zeta potential of -25.5 mV, an encapsulation efficiency of 90.5%, and a PDI after one month of 0.19. These results are in complete agreement with the predicted values of the model. Its aerodynamic properties were as follows: the mass median aerodynamic diameter (MMAD) was 4.41 µm, the fine particle fraction (FPF) was 53.46%, and the percentage of particles equal to or less than 3 µm was 34.3%. This demonstrates that the novel EGCG liposome has all the properties required to be inhalable, and it is expected to be deposited deeply in the lung. The TGFß pathway is activated in PAH lungs, and the optimum EGCG nano-liposome inhibits TGFß signalling in cell-based studies and thus holds promise as a potential treatment for PAH.

Molecular genetic characterization of SMAD signaling molecules in pulmonary arterial hypertension.

Heterozygous germline mutations of BMPR2 contribute to familial clustering of pulmonary arterial hypertension (PAH). To further explore the genetic basis of PAH in isolated cases, we undertook a candidate gene analysis to identify potentially deleterious variation. Members of the bone morphogenetic protein (BMP) pathway, namely SMAD1, SMAD4, SMAD5, and SMAD9, were screened by direct sequencing for gene defects. Four variants were identified in SMADs 1, 4, and 9 among a cohort of 324 PAH cases, each not detected in a substantial control population. Of three amino acid substitutions identified, two demonstrated reduced signaling activity in vitro. A putative splice site mutation in SMAD4 resulted in moderate transcript loss due to compromised splicing efficiency. These results demonstrate the role of BMPR2 mutation in the pathogenesis of PAH and indicate that variation within the SMAD family represents an infrequent cause of the disease.

Targeting the TGF-ß signaling pathway for resolution of pulmonary arterial hypertension.

Aberrant transforming growth factor-ß (TGF-ß) signaling activation is linked to pulmonary arterial hypertension (PAH). BMPR2 mutations perturb the balance between bone morphogenetic protein (BMP) and TGF-ß pathways, leading to vascular remodeling, narrowing of the lumen of pulmonary vasculature, and clinical symptoms. This forum highlights the association of the TGF-ß pathway with pathogenesis and therapeutic approaches.

A double reporter assay for detecting changes in the ratio of spliced and unspliced mRNA in mammalian cells.

Current methods for measuring the efficiency of splicing in mammalian cells rely on either direct analysis of the RNA, which does not lend itself to rapid assays, or on single reporter functions that are subject to numerous intrinsic variables. If two protein activities are encoded within a single reading frame but on separate exons, with an intervening sequence containing termination codons, then the expression of the second activity is dependent on removal of the intervening sequence by pre-mRNA splicing. Thus, the ratio of the activities encoded by exon 2 to exon 1 reflects the ratio of expression from spliced mRNA to the total expression of spliced and unspliced RNA. This provides a rapid and convenient assay for the effects on splicing efficiency of trans-acting factors or of alterations in the sequences of the intron and surrounding exon sequences.

AKAP95 regulates splicing through scaffolding RNAs and RNA processing factors.

Alternative splicing of pre-mRNAs significantly contributes to the complexity of gene expression in higher organisms, but the regulation of the splice site selection remains incompletely understood. We have previously demonstrated that a chromatin-associated protein, AKAP95, has a remarkable activity in enhancing chromatin transcription. In this study, we show that AKAP95 interacts with many factors involved in transcription and RNA processing, including selective groups of hnRNP proteins, through its N-terminal region, and directly regulates pre-mRNA splicing. AKAP95 binds preferentially to proximal intronic regions on pre-mRNAs in human transcriptome, and this binding requires its zinc-finger domains. By selectively coordinating with hnRNP H/F and U proteins, AKAP95 appears to mainly promote the inclusion of many exons in the genome. AKAP95 also directly interacts with itself. Taken together, our results establish AKAP95 as a mostly positive regulator of pre-mRNA splicing and a possible integrator of transcription and splicing regulation.

Corrigendum to "Data for proteomic analysis of murine cardiomyocytic HL-1 cells treated with siRNA against tissue factor" [Data Brief 3 (2015) 117-119].

[This corrects the article DOI: 10.1016/j.dib.2015.02.005.].

Data for proteomic analysis of murine cardiomyocytic HL-1 cells treated with siRNA against tissue factor.

This data article is related to the research article entitled Proteomics of Tissue Factor silencing in cardiomyocytic cells reveals a new role for this coagulation factor in splicing machinery control by Lento et al. [1]. Tissue Factor (TF) is a key player in the coagulation cascade, but it has additional functions ranging from angiogenesis, tumour invasion and, in the heart, the maintenance of the integrity of cardiac cells. This article reports the nano-LC-MS(E) analysis of the cardiomyocytic HL-1 cell line proteome and describes the results obtained from a Gene Ontology analysis of those proteins affected by TF-gene silencing.

Proteomics of tissue factor silencing in cardiomyocytic cells reveals a new role for this coagulation factor in splicing machinery control.

It has long been known that Tissue Factor (TF) plays a role in blood coagulation and has a direct thrombotic action that is closely related to cardiovascular risk, but it is becoming increasingly clear that it has a much wider range of biological functions that range from inflammation to immunity. It is also involved in maintaining heart haemostasis and structure, and the observation that it is down-regulated in the myocardium of patients with dilated cardiomyopathy suggests that it influences cell-to-cell contact stability and contractility, and thus contributes to cardiac dysfunction. However, the molecular mechanisms underlying these coagulation-independent functions have not yet been fully elucidated. In order to analyse the influence of TF on the cardiomyocitic proteome, we used functional biochemical approaches incorporating label-free quantitative proteomics and gene silencing, and found that this provided a powerful means of identifying a new role for TF in regulating splicing machinery together with the expression of several proteins of the spliceosome, and mRNA metabolism with a considerable impact on cell viability. BIOLOGICAL SIGNIFICANCE: In this study, using quantitative proteomics and functional biochemical approaches, we define for the first time that, in addition to its primary role in blood coagulation, Tissue Factor also plays a novel role in regulating cell splicing machinery, with a relevant impact on cell survival. This new function may help to explain the wide range of biological activities of TF, and thus provide fruitful clues for developing new strategies for treating human diseases in which TF is dysregulated.

A double-reporter splicing assay for determining splicing efficiency in mammalian cells.

Changes in alternative splicing patterns can result from both inherited and acquired defects, and they are increasingly recognized as causes of human diseases. Hence, improvements in the understanding of alternative splicing regulation may provide opportunities for restoring productive patterns of splicing. The identification of factors (such as proteins, nucleic acids or small molecules) that modulate the splicing pattern would be facilitated by systems with which many samples can be screened. The absence of reliable systems prompted us to develop an assay system based on dual enzymatic activities. Two distinct signals derived from spliced and unspliced RNA are measured, providing the basis for a robust, rapid and convenient assay for investigating splicing. This protocol describes how to use this system; the time required for lysing the cells and recording enzymatic activity is about 2 hours.