Enhanced Tissue Factor Pathway Activity and Fibrin Turnover in the Alveolar Compartment of Patients with Interstitial Lung Disease

Bronchoalveolar lavage fluids (BALF) from patients with hyper- sensitivity pneumonitis (HP; n = 35), idiopathic pulmonary fibrosis (IPF, n = 41) and sarcoidosis (SARC, n = 48) were investigated for alterations in the alveolar hemostatic balance. Healthy individuals (n = 21) served as Controls. Procoagulant activity (PCA), tissue factor (TF) activity and F VII activity were assessed by means of specific recalcification assays. The overall fibrinolytic activity (FA) was measured using the 125I-labeled fibrin plate assay. Fibrinopeptide A (FP-A), D-Dimer, plasminogen activators (PA) of the urokinase (u-PA) or tissue type (t-PA), PA-Inhibitor I (PAI-1) and α2-antiplasmin (α2-AP) were determined by ELISA technique. As compared to Controls, all groups with interstitial lung disease (ILD) displayed an increase in BALF PCA by approximately one order of magnitude, and this was ascribed to enhanced TF activity by >98%. Accordingly, F VII-activity was increased in all ILD groups, and elevated FP-A levels were noted. There was no significant difference in procoagulant activi- ties between the different ILD entities, but the increase in TF was significantly correlated with deterioration of lung compliance. Overall fibrinolytic activity did not significantly differ between ILD entities and Controls, although some reduction in IPF subjects was observed. Nevertheless, changes in the profile of the different pro- and anti- fibrinolytic compounds were noted. U-PA, but not t-PA levels were significantly reduced in all ILD groups. α2-AP was markedly elevated throughout, whereas PAI-1 levels were lowered. As a balance of enhanced procoagulant and sustained overall fibrinolytic activity, lavage D-dimer levels were elevated by more than one order of magnitude in all ILD patients. We conclude that the predominant alteration in alveolar hemostatic balance in all groups of ILD patients is an enhancement in TF factor pathway activity. Concomitantly, various compounds of the (anti-)fibrinolytic pathways present with altered concentrations, but the overall BALF fibrinolytic activity is largely unchanged. The net enhancement of fibrin turnover is significantly correlated with the decrease in lung compliance.

Abbreviations: α2-AP – α2-antiplasmin; ARDS – acute respiratory distress syndrome; BAL – bronchoalveolar lavage; BALF – BAL fluids; BSA – bovine serum albumin; FEV1 – forced expired volume within 1 s; FP-A – fibrinopeptide A; FVC – forced vital capacity; ILD – interstitial lung disease; IPF – idiopathic pulmonary fibrosis; HP – hypersensitivity pneumonitis; PAI-1 – plasminogen-activator-inhibitor-1; PBS – phosphate buffered saline; PCA – procoagulant activity; PL – phospholipid; PPQ – phospholipid-proteinquotient; SARC – sarcoidosis; t-PA – tissue-type plasminogen activator; u-PA – urokinase-type plasminogen activator

[Update pulmonary arterial hypertension : Definitions, diagnosis, therapy]

The term pulmonary arterial hypertension comprises a group of pulmonary vascular diseases of different etiologies that are characterized by similar precapillary vascular remodeling processes and result in exertional dyspnea and right heart insufficiency. The specific pharmacological treatment approach considers the risk of mortality and phenotypical properties and includes treatment with phosphodiesterase type 5 inhibitors, endothelin receptor antagonists and prostanoids, as well as with more novel substances, such as a soluble guanylyl cyclase stimulator and an oral prostacyclin receptor agonist. The prognosis of the disease is mainly determined by the right heart insufficiency for which there is currently no specific pharmacological treatment. Lung transplantation may be offered as a last option. This review provides an overview of the current European guidelines from 2015 and the recommendations of the Cologne Consensus Conference for pulmonary hypertension from 2016.

[Medical treatment of pulmonary hypertension: what's new?]

Pulmonary hypertension (PH) is a chronic progressive disease of the pulmonary circulation of multifactorial causes. The current diagnostic classification of PH distinguishes five main groups, which have as a common feature an increased pulmonary arterial pressure and pulmonary resistance. The classification differentiates pulmonary arterial hypertension (PAH), PH due to left heart disease, PH in lung diseases and/or hypoxia, chronic thromboembolic pulmonary hypertension (CTEPH), and PH with unclear/multifactorial mechanisms. Recent advances in basic research with the approval of new drugs and the establishment of therapeutic strategies, mainly in PAH and CTEPH, require a differentiated view of the disease, a careful diagnosis and initiation of therapy, and regular follow-ups. In this article, we provide an overview of the complex drug therapy currently available for PAH patients.

Phosphodiesterase-4 promotes proliferation and angiogenesis of lung cancer by crosstalk with HIF

Lung cancer is the leading cause of cancer death worldwide. Recent data suggest that cyclic nucleotide phosphodiesterases (PDEs) are relevant in various cancer pathologies. Pathophysiological role of phosphodiesterase 4 (PDE4) with possible therapeutic prospects in lung cancer was investigated. We exposed 10 different lung cancer cell lines (adenocarcinoma, squamous and large cell carcinoma) to hypoxia and assessed expression and activity of PDE4 by real-time PCR, immunocytochemistry, western blotting and PDE activity assays. Expression and activity of distinct PDE4 isoforms (PDE4A and PDE4D) increased in response to hypoxia in eight of the studied cell lines. Furthermore, we analyzed various in silico predicted hypoxia-responsive elements (p-HREs) found in in PDE4A and PDE4D genes. Performing mutation analysis of the p-HRE in luciferase reporter constructs, we identified four functional HRE sites in the PDE4A gene and two functional HRE sites in the PDE4D gene that mediated hypoxic induction of the reporter. Silencing of hypoxia-inducible factor subunits (HIF1α and HIF2α) by small interfering RNA reduced hypoxic induction of PDE4A and PDE4D. Vice versa, using a PDE4 inhibitor (PDE4i) as a cyclic adenosine monophosphate (cAMP) -elevating agent, cAMP analogs or protein kinase A (PKA)-modulating drugs and an exchange protein directly activated by cAMP (EPAC) activator, we demonstrated that PDE4-cAMP-PKA/EPAC axis enhanced HIF signaling as measured by HRE reporter gene assay, HIF and HIF target genes expression ((lactate dehydrogenase A), LDHA, (pyruvate dehydrogenase kinase 1) PDK1 and (vascular endothelial growth factor A) VEGFA). Notably, inhibition of PDE4 by PDE4i or silencing of PDE4A and PDE4D reduced human lung tumor cell proliferation and colony formation. On the other hand, overexpression of PDE4A or PDE4D increased human lung cancer proliferation. Moreover, PDE4i treatment reduced hypoxia-induced VEGF secretion in human cells. In vivo, PDE4i inhibited tumor xenograft growth in nude mice by attenuating proliferation and angiogenesis. Our findings suggest that PDE4 is expressed in lung cancer, crosstalks with HIF signaling and promotes lung cancer progression. Thus, PDE4 may represent a therapeutic target for lung cancer therapy.

Soluble guanylate cyclase stimulation: an emerging option in pulmonary hypertension therapy

The prognosis for patients with pulmonary hypertension remains poor despite recent treatment advances, and there is a need for therapies with new modes of action. Nitric oxide (NO) is an endogenous vasodilator, the levels of which are regulated throughout the lung to ensure preferential perfusion of well-ventilated regions. Drugs that act in synergy with endogenous NO would therefore promote pulmonary vasodilation while maintaining optimal gas exchange. Riociguat is an oral stimulator of the NO receptor soluble guanylate cyclase. It synergises with NO and has demonstrated vasodilatory and antiremodelling properties in preclinical studies. Riociguat has been shown to have a favourable safety profile in healthy volunteers and in patients with pulmonary hypertension. Pharmacokinetic analyses have revealed substantial interindividual variation, suggesting that individual dose titration will be required. In a proof-of-concept study of patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension, riociguat improved cardiopulmonary haemodynamics from baseline. It also caused systemic vasodilation, which was well tolerated but should be monitored in future studies. Dose titration of riociguat should promote pulmonary vasodilation while maintaining control of systemic effects, and has been investigated in a phase-II study of patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. Preliminary results indicate that phase-III trials are warranted.

Terguride ameliorates monocrotaline-induced pulmonary hypertension in rats

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterised by vasoconstriction and remodelling of the pulmonary vasculature. The serotonin (5-hydroxytryptamine (5-HT)) pathway has been shown to play a major role in the pathogenesis of PAH, but pharmacological modulation of this pathway for treatment of PAH is, to date, at a pre-clinical level. Terguride is a 5-HT receptor (5-HTR) antagonist that is well tolerated and clinically approved for ovulation disorders. Immunohistochemistry against 5-HTR(₂A/B) on human lungs revealed their localisation to the vascular smooth muscle layer and quantitative RT-PCR showed 5-HTR(₂B) upregulation in pulmonary artery smooth muscle cells (PASMC) isolated from PAH patients. Proliferation and migration of cultured primary human PASMC were dose-dependently blocked by terguride. Therapeutic 5-HT signalling inhibition was 1) demonstrated in isolated, ventilated and perfused rat lungs and 2) by chronic terguride treatment of rats with monocrotaline (MCT)-induced pulmonary hypertension in a preventive or curative approach. Terguride inhibited proliferation of PASMCs and abolished 5-HT-induced pulmonary vasoconstriction. Chronic terguride treatment prevented dose-dependently the development and progression of MCT-induced PAH in rats. Thus, terguride represents a valuable novel therapeutic approach in PAH.