A review of therapeutic agents for the management of pulmonary arterial hypertension

Immune Cells in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex and serious cardiopulmonary disease; it is characterised by increased pulmonary arterial pressure and pulmonary vascular remodelling accompanied by disordered endothelial and smooth muscle cell proliferation within pulmonary arterioles and arteries. Although recent reports have suggested that dysregulated immunity and inflammation are key players in PAH pathogenesis, their roles in PAH progression remain unclear. Intriguingly, altered host immune cell distribution, number, and polarisation within the lung arterial vasculature have been linked to disease development. This review mainly focusses on the roles of different immune cells in PAH and discusses the underlying mechanisms.

Sphingosine-1-phosphate promotes pulmonary artery smooth muscle cells proliferation by stimulating autophagy-mediated E-cadherin/CDH1 down-regulation

It has been shown that sphingosine-1-phosphate (S1P) is elevated in patients with pulmonary arterial hypertension (PAH) and promotes the proliferation of pulmonary artery smooth muscle cells (PASMCs). Meanwhile, S1P has been found to induce the activation of autophagy in several types of human diseases including cancers. However, it is still unclear whether activation of autophagy mediates S1P-induced PASMCs proliferation, and detailed mechanisms responsible for these processes are indefinite. The aims of this study are to address these issues. S1P dose- and time-dependently reduced the expression of E-cadherin/CDH1 and stimulated PASMCs proliferation; this was accompanied with the elevation of TNF receptor-associated factor 2 (TRAF2), up-regulation and ubiquitination of BECN1 and the activation of autophagy. Prior silencing TRAF2 or BECN1 using siRNA or pre-incubation of cells with autophagy inhibitor chloroquine phosphate (CQ) suppressed S1P-induced autophagy activation and subsequent CDH1 degradation and further PASMCs proliferation. Taken together, our study indicates that S1P promotes the activation of autophagy by accelerating TRAF2-mediated BECN1 up-regulation and ubiquitination, which in turn results in CDH1 reduction and contributes to PASMCs proliferation.

Leukotriene B4 induces proliferation of rat pulmonary arterial smooth muscle cells via modulating GSK-3β/β-catenin pathway

Leukotriene B₄ (LTB₄) has been found to contribute to pulmonary arterial smooth muscle cells (PASMCs) proliferation and pulmonary arterial remodeling therefore the development of pulmonary arterial hypertension (PAH). Yet, the underlying molecular mechanisms remain poorly understood. The present study aims to address this issue. Our results demonstrate that LTB₄ dose- and time-dependently induced proliferation of primary cultured rat PASMCs, this was accompanied with the activation of phosphatidylinositol-3-kinase/Akt (PI3K/Akt) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathways, and consequent inactivation of glycogen synthase kinase-3β (GSK-3β), up-regulation of β-catenin and induction of cyclin D1 expression. The presence of PI3K inhibitor (LY294002) or MEK inhibitor (U0126) or prior silencing of β-catenin with siRNA suppressed LTB₄-induced cyclin D1 up-regulation and PASMCs proliferation. In addition, inactivation or lack of GSK-3β up-regulated β-catenin and cyclin D1 in PASMCs. Taken together, our study indicates that activation of PI3K/Akt and ERK1/2 pathways mediates LTB₄-induced PASMCs proliferation by modulating GSK-3β/β-catenin/cyclin D1 axis and suggests that targeting this pathway might have potential value in alleviating vascular remodeling and benefit PAH.

Validity and reliability of the Turkish version of the EmPHasis-10 questionnaire in patients with pulmonary hypertension

RATIONALE, AIMS, AND OBJECTIVES

The aim of the study was to evaluate the reliability and validity of the Turkish version of the EmPHasis-10 questionnaire to ensure cultural adaptation.

METHODS

This study involved translation, back translation, and cross-cultural adaptation. One hundred and one patients who were diagnosed as having pulmonary hypertension (PH) for at least 6 months were evaluated using the Turkish version of EmPHasis-10. Turkish version of the Minnesota Living with Heart Failure Questionnaire (MLHFQ) was used as gold standard to assess the validation of the Turkish version of the EmPHasis-10 questionnaire. Relationship between MLHFQ and EmPHasis-10 was analysed using Spearman correlation analysis to assess the validation. Cronbach alpha (internal consistency) and exploratory factor analyses were used to assess the questionnaire's reliability.

RESULTS

The statistical analysis showed that the EmPHasis-10 questionnaire showed a high validity with MLHFQ (r = 0.85) (P = 0.001). Reliability analysis showed that EmPHasis-10 had a high level of Cronbach alpha (α = 0.98) and internal consistency (ICC = 0.97).

CONCLUSIONS

The Turkish version of EmPHasis-10 is a quality of life questionnaire specific to PH. It has a high-level validity and reliability questionnaire that can be used by researchers and physicians.

S1P induces pulmonary artery smooth muscle cell proliferation by activating calcineurin/NFAT/OPN signaling pathway

The upregulation of osteopontin(OPN) has been found to contribute to the proliferation of pulmonary artery smooth muscle cells(PASMCs), and activation of PPARγ has been shown to suppress OPN expression in THP-1 cells. However, the molecular mechanisms underlying the upregulation of OPN expression and PPARγ agonist modulation of OPN expression in PASMCs remain largely unclear. Here we found that S1P stimulated PASMCs proliferation and up-regulated OPN expression in rat PASMCs, which was accompanied with the activation of phospholipase C(PLC), calcineurin and translocation of NFATc3 to nucleus. Further study showed that inhibition of PLC by U73122, suppression of calcineurin activity by cyclosporine A(CsA) or knockdown of NFATc3 using small interfering RNA suppressed S1P-induced OPN up-regulation. Activation of PPARγ by pioglitazone suppressed S1P-induced activation of calcineurin/NFATc3 signaling pathway and followed OPN up-regulation. Taken together, our study indicates that S1P stimulates OPN expression by activation of PLC/calcineurin/NFATc3 signaling pathway, and activation of PPARγ suppresses calcineurin/NFATc3-mediated OPN expression in PASMCs.

Autophagy and pulmonary disease

Autophagy is a process of cell self-renewal that is dependent on the degradation of the cytoplasmic proteins or organelles of lysosomes. Many diseases, such as metabolic diseases, cancer, neurodegenerative diseases, and lung diseases, have been confirmed to be associated with elevated or impaired levels of autophagy. At present, studies have found that autophagy participates in the regulation of chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis, pulmonary hypertension, acute lung injury, lung cancer, and other pulmonary diseases. Using recent literature on the signal transduction mechanisms of autophagy and the effects of autophagy signalling on lung diseases, this review intends to clarify the mechanisms of lung disease to guide the treatment of related diseases. The reviews of this paper are available via the supplemental material section.

Repurposing rosiglitazone, a PPAR-γ agonist and oral antidiabetic, as an inhaled formulation, for the treatment of PAH

Peroxisome-proliferator-activated-receptor-gamma (PPAR-γ) is implicated, in some capacity, in the pathogenesis of pulmonary arterial hypertension (PAH). Rosiglitazone, an oral antidiabetic and PPAR-γ agonist, has the potential to dilate pulmonary arteries and to attenuate arterial remodeling in PAH. Here, we sought to test the hypothesis that rosiglitazone can be repurposed as inhaled formulation for the treatment of PAH. We have tested this conjecture by preparing and optimizing poly(lactic-co-glycolic) acid (PLGA) based particles of rosiglitazone, assessing the drug particles for pulmonary absorption, investigating the efficacy of the plain versus particulate drug formulation in improving the respiratory hemodynamics in PAH animals, and finally studying the effect of the drug in regulating the molecular markers associated with PAH pathogenesis. The optimized particles were slightly porous and spherical, and released 87.9% ± 6.7% of the drug in 24 h. The elimination half-life of the drug formulated in PLGA particles was 2.5-fold greater than that of the plain drug administered via the same route at the same dose. The optimized formulation, given via the pulmonary route, produced pulmonary selective vasodilation in PAH animals, but oral rosiglitazone had no effect in pulmonary hemodynamics. Rosiglitazone ameliorates the pathogenesis of PAH by balancing the molecular regulators involved in the vasoconstriction and vasodilation of human pulmonary arterial smooth muscle cells. All in all, data generated using intact animal and cellular models point to the conclusion that PLGA particles of an antidiabetic drug can be used for the treatment of a different disease, PAH.