Extracellular matrix degradation pathways and fatty acid metabolism regulate distinct pulmonary vascular cell types in pulmonary arterial hypertension.

Pulmonary arterial hypertension describes a group of diseases characterised by raised pulmonary vascular resistance, resulting from vascular remodelling in the pre-capillary resistance arterioles. Left untreated, patients die from right heart failure. Pulmonary vascular remodelling involves all cell types but to date the precise roles of the different cells is unknown. This study investigated differences in basal gene expression between pulmonary arterial hypertension and controls using both human pulmonary microvascular endothelial cells and human pulmonary artery smooth muscle cells. Human pulmonary microvascular endothelial cells and human pulmonary artery smooth muscle cells from pulmonary arterial hypertension patients and controls were cultured to confluence, harvested and RNA extracted. Whole genome sequencing was performed and after transcript quantification and normalisation, we examined differentially expressed genes and applied gene set enrichment analysis to the differentially expressed genes to identify putative activated pathways. Human pulmonary microvascular endothelial cells displayed 1008 significant (p ≤ 0.0001) differentially expressed genes in pulmonary arterial hypertension samples compared to controls. In human pulmonary artery smooth muscle cells, there were 229 significant (p ≤ 0.0001) differentially expressed genes between pulmonary arterial hypertension and controls. Pathway analysis revealed distinctive differences: human pulmonary microvascular endothelial cells display down-regulation of extracellular matrix organisation, collagen formation and biosynthesis, focal- and cell-adhesion molecules suggesting severe endothelial barrier dysfunction and vascular permeability in pulmonary arterial hypertension pathogenesis. In contrast, pathways in human pulmonary artery smooth muscle cells were mainly up-regulated, including those for fatty acid metabolism, biosynthesis of unsaturated fatty acids, cell-cell and adherens junction interactions suggesting a more energy-driven proliferative phenotype. This suggests that the two cell types play different mechanistic roles in pulmonary arterial hypertension pathogenesis and further studies are required to fully elucidate the role each plays and the interactions between these cell types in vascular remodelling in disease progression.

Right ventricular systolic to diastolic duration ratio: A novel predictor of outcome in adult idiopathic pulmonary arterial hypertension.

BACKGROUND: The systolic to diastolic (SD) duration ratio reflects global RV performance in pulmonary arterial hypertension (PAH) yet limited data exists on its application to adult non-congenital PAH. We measured SD ratios on echocardiogram in idiopathic PAH (IPAH) to establish its response to pulmonary vasodilator therapy and prognostic value at diagnosis and follow up. METHODS: Incident patients with IPAH undergoing echocardiogram, haemodynamic and exercise assessments were identified within our centre between 2005 and 2018. SD ratios were adjusted for heart rate at diagnosis and follow up. RESULTS: In 98 patients at diagnosis, the mean SD ratio was 1.03 ±â€¯0.37 decreasing to 0.85 ±â€¯0.25, p < 0.001 at follow-up echocardiogram performed at a median interval of 9.0 months. The SD ratio at diagnosis correlated weakly with RV basal diameter (r = 0.24, p = 0.04) and 6MWD (r = 0.23, p = 0.04). At follow up, the mean SD ratio was lower in those receiving combination vs monotherapy pulmonary vasodilator treatment (71 ±â€¯25 vs 92 ±â€¯22% baseline respectively, p < 0.001). After a median follow-up of 4.8 years, 3 patients were transplanted and 23 patients died. The SD ratio at diagnosis and follow up predicted an increased risk of death/transplantation (HR 2.41 (1.09-5.29), p = 0.03; HR 5.02 (1.27-19.77), p = 0.02 respectively), retaining its predictive value at diagnosis in bivariate models with 6MWD (HR 2.18 (1.06-4.08)), WHO Functional Class (HR 2.33 (1.04-5.21)) and TAPSE (HR 2.36 (1.07-5.19)), all p < 0.05. CONCLUSIONS: The SD ratio carries prognostic value at diagnosis and follow up in IPAH. Its further evaluation alongside current PAH risk stratification parameters should be considered.

Elevated nocturnal desaturation index predicts mortality in interstitial lung disease.

BACKGROUND: Nocturnal desaturation may contribute to long-term pulmonary vascular stress in interstitial lung disease (ILD). We study the prevalence, severity and prognostic utility of nocturnal desaturation across ILD. METHODS: ILD patients with overnight oximetry (June 2006-August 2008) were reviewed (n = 134). Significant nocturnal desaturation was considered as > 10% of sleep with SpO2 < 90%. Desaturation index (DI) was defined as the number of desaturation events > 4%/hr. Covariates, including indices of nocturnal desaturation, were evaluated against mortality. RESULTS: Nocturnal desaturation was present in 49 (37%) patients. 31% of patients had pulmonary hypertension (PH) on echocardiography. Increased DI was associated with higher mortality independent of age, gender and BMI (HR 1.04; 95% CI 1.00, 1.06; p = 0.009). In separate models, DI and a) elevated brain natriuretic peptide (BNP; HR 1.04; 95% CI 1.00, 1.08; p = 0.04); b) moderate-severe PH on echocardiography (HR 3.15; 95% CI 1.24, 8.00; p = 0.02); and c) daytime resting SpO2 (HR 0.92; 95% CI 0.85, 0.99; p = 0.04) independently predicted mortality following adjustment for age, gender and BMI. CONCLUSION: Nocturnal desaturation is common and may be severe in ILD. Elevated nocturnal DI predicts higher mortality across ILD, independent of other vascular parameters. This finding may have important implications for the pathogenesis of PH in IPF.

Dexamethasone reverses monocrotaline-induced pulmonary arterial hypertension in rats.

Pulmonary arterial hypertension (PAH) is associated with dysregulated bone morphogenetic protein receptor (BMPR)-II signaling and pulmonary vascular inflammation. We evaluated the effects of dexamethasone on monocrotaline (MCT)-induced PAH in rats for potential reversal of PAH at late time-points. Saline-treated control, MCT-exposed, MCT-exposed and dexamethasone-treated rats (5 mg·kg⁻¹·day⁻¹, 1.25 mg·kg⁻¹ and 2.5 mg·kg⁻¹·48 h⁻¹) were evaluated at day 28 and day 35 following MCT for haemodynamic parameters, right ventricular hypertrophy, morphometry, immunohistochemistry, and IL6 and BMPR2 expression. Dexamethasone improved haemodynamics and pulmonary vascular remodelling, preventing PAH development at early (day 1-14 and 1-28) and reversing PAH at late (day 14-28 and 21-35) time-points following MCT, as well as improving survival in MCT-exposed rats compared with controls. Both MCT-induced pulmonary IL6 overexpression and interleukin (IL)-6-expressing adventitial inflammatory cell infiltration were reduced with dexamethasone. This was associated with pulmonary BMPR2 downregulation following MCT, which was increased with dexamethasone, in whole lung and control pulmonary artery smooth muscle cells. Dexamethasone also reduced proliferation of rat pulmonary artery smooth muscle cells in vitro. Experimental PAH can be prevented and reversed by dexamethasone, and survival is improved. In this model, mechanisms may involve reduction of IL-6-expressing inflammatory cells, restoration of pulmonary BMPR2 expression and reduced proliferation of vascular smooth muscle cells.

Elevated brain natriuretic peptide predicts mortality in interstitial lung disease.

Elevated pulmonary vascular resistance portends a poor prognosis across interstitial lung disease (ILD), irrespective of the histospecific diagnosis. Currently, no noninvasive surrogate prognostic marker exists. We explore the prognostic value of brain natriuretic peptide (BNP) and echocardiography across ILD. ILD patients with BNP concentrations performed during 2005-2007 were reviewed (n = 90). Echocardiography tapes were reviewed by a cardiologist blinded to other results. Outcome was evaluated for survival against BNP and echocardiograph parameters. A priori threshold values and composite markers were evaluated against survival. During follow-up (20±9 months) there were 28 deaths (31%). BNP correlated with right heart echocardiographic indices, including right ventricular systolic pressure (RVSP) (R(2) = 0.18, p = 0.0002) but not with parameters of left heart function. Nonsurvivors had higher BNP and RVSP levels than survivors. BNP ≥20 pmol·L(-1) (hazard ratio (HR) 2.93, 95% CI 1.28-6.73; p = 0.01) and moderate-severe pulmonary hypertension (HR 2.53, 95% CI 1.15-5.57; p = 0.02) were associated with increased mortality, independent of age, sex and pulmonary function. Patients with BNP ≥20 pmol·L(-1) had a 14-fold increased mortality over those with BNP <4 pmol·L(-1). Increased BNP levels and/or echocardiographic markers of right ventricular dysfunction were associated with increased mortality across ILD. The link between vascular parameters and mortality supports the concept that pulmonary vascular disease contributes to the final common pathway seen across ILD.

Pulmonary hypertension in idiopathic pulmonary fibrosis: a review.

Pulmonary hypertension (PH) is a common in patients with idiopathic pulmonary fibrosis (IPF) referred for transplantation. When present, PH is associated with increased mortality, and may explain the deterioration of some patients with preserved pulmonary function. PH in IPF may develop as a consequence of, or disproportionate to the underlying fibrotic lung disease. The distinction between these two 'stages' of PH is essential as there are key differences in their pathophysiology, identification, and potential treatment options. Treatment advances in idiopathic pulmonary artery hypertension have focused attention on PH associated with underlying lung disease. We focus on pathogenetic mechanisms, identification of PH, and the potential for therapeutic intervention for PH in IPF. Although vascular ablation, and chronic hypoxia are both important in the aetiology of secondary PH, these mechanisms do not explain the development of disproportionate PH. In these patients, the early development of PH may be associated with increased fibrotic cell mediators, abnormal vasculature or response to hypoxia, seen in IPF. Nocturnal and exercise desaturation are common in IPF, and may precede and contribute to the development PH. Therapeutic options for PH in IPF are limited, and there have been no controlled trials. Successful therapeutic intervention in pulmonary arterial hypertension, has led to suggestions that therapeutic intervention with PH specific therapy may be useful. However, controlled trials are warranted before therapy can be recommended. In the design of such trials, the distinction between secondary and disproportionate PH is essential.

Extracorporeal carbon dioxide removal to "protect" the lung.

The case histories are presented of three adults who had severe hypercapnic acidosis despite mechanical ventilation with what were considered to be injurious tidal volumes and airway pressures. The use of a percutaneously inserted arteriovenous extracorporeal carbon dioxide removal (AV-ECCO(2)R) device facilitated a dramatic reduction in the amount of ventilatory support required, achieving a "lung-protective" level. Two patients survived to hospital discharge. One patient died after it became apparent that her late-stage interstitial lung disease was unresponsive to immunosuppression. AV-ECCO(2)R may be a useful strategy in facilitating lung-protective ventilation.

Pulmonary vascular resistance predicts early mortality in patients with diffuse fibrotic lung disease and suspected pulmonary hypertension.

BACKGROUND: Pulmonary hypertension (PH) is associated with a poor prognosis in diffuse lung disease (DLD). A study was undertaken to compare the prognostic significance of invasive and non-invasive parameters in patients with DLD and suspected PH. METHODS: Hospital records of consecutive patients with DLD undergoing right heart catheterisation (RHC) were reviewed (n = 66). Mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR) and non-invasive variables were examined against early (within 12 months) and overall mortality. A priori thresholds were examined against early mortality. Relationships between mPAP, PVR and non-invasive markers were assessed. RESULTS: Fifty patients had PH on RHC (mean (SD) mPAP 33.5 (11.8) mm Hg, PVR 5.9 (4.3) Wood units (WU)). Raised PVR was strongly associated with early mortality (odds ratio (OR) 1.30; 95% confidence interval (CI) 1.11 to 1.52; p = 0.001), with PVR > or = 6.23 WU being the optimal threshold after adjustment for age, gender, composite physiological index (CPI) and diagnosis of idiopathic pulmonary fibrosis (OR 11.09; 95% CI 2.54 to 48.36; p = 0.001). Early mortality was linked, albeit less strongly, to right ventricular dilation at echocardiography, but not to other non-invasive variables or mPAP. Overall mortality was most strongly associated with increasing CPI levels. Correlations between PVR and non-invasive variables were moderate (R(2) <0.32), improving little following construction of a multivariate index which did not itself predict mortality. CONCLUSION: In severe DLD, early mortality is strongly linked to increased PVR but not to other RHC or non-invasive variables. These findings suggest that the threshold for RHC in severe DLD should be low, enabling prioritisation of aggressive treatment including lung transplantation.

Endogenously released endothelin-1 from human pulmonary artery smooth muscle promotes cellular proliferation: relevance to pathogenesis of pulmonary hypertension and vascular remodeling.

Endothelin (ET)-1 is a potent vasoconstrictor and comitogen/ proliferation factor for vascular smooth muscle (VSM). As such, it has been implicated in the vascular wall remodeling observed in pulmonary hypertension (PH). Although the endothelium is considered the main source of ET-1, it can be released by other cells including VSM and may mediate proliferation in an autocrine manner. We investigated this possibility using human pulmonary artery smooth-muscle (HPASM) cells. Serum stimulated the release of ET-1 from HPASM cells in a concentration-dependent fashion and caused proliferation as determined by [(3)H]thymidine uptake and increase in cell number. Addition of an ET-A receptor antagonist (BQ123) or an inhibitor of ET-1 synthesis (phosphoramidon) reduced the proliferation induced by serum, confirming an autocrine role for ET-1. In addition, treatment of HPASM cells with two drug types used in the management of PH-cicaprost, a stable prostacyclin-mimetic; or diltiazem, a calcium-channel blocker-reduced ET-1 release from these cells. We conclude that ET-1 released from HPASM cells has an autocrine function in serum-induced proliferation, with important implications for the pathogenesis of human vascular remodeling. Drugs used in the treatment of PH may act, at least in part, by inhibiting this autocrine loop.

The prostacyclin-mimetic cicaprost inhibits endogenous endothelin-1 release from human pulmonary artery smooth muscle cells.

There is increasing evidence supporting a role for endothelin-1 (ET-1) in human pulmonary hypertension. The aim of this study was to determine the relative roles of human pulmonary microvascular endothelial cells (HPMVE) and human pulmonary artery smooth muscle (HPASM) cells to produce ET-1 under inflammatory conditions and to investigate further possible control mechanisms of ET-1 production by HPASM. Although HPMVE cells produced more ET-1 than HPASM when cultured with fetal calf serum (FCS) alone and after treatment with cytokines; HPASM produced significant amounts of ET-1 after stimulation with cytokines. Cytokine-stimulated increase in ET-1 production by HPASM was inhibited by cicaprost, a prostacyclin analogue, and other agents that are known to increase intracellular cyclic AMP. Cicaprost also inhibited proliferation of HPASM in response to FCS lending support to the theory that part of the clinical benefit seen in long-term treatment with prostacyclin in pulmonary hypertension may be a result of inhibition of ET-1 production in these cells.

The role of the endothelium in modulating vascular control in sepsis and related conditions.

The majority of deaths amongst critically ill patients requiring intensive care are attributable to sepsis and its sequelae: septic shock, the systemic inflammatory response syndrome (SIRS) and the acute respiratory distress syndrome (ARDS). Patients within the ICU who develop these conditions and fail to survive succumb to multiple organ dysfunction syndrome (MODS). ARDS is considered to be the pulmonary component of MODS and is characterized by pulmonary hypertension, often in the setting of systemic hypotension. Endothelial cells, normally responsible for modulating vascular tone, becomes dysfunctional in sepsis. Pro-thrombotic, pro-inflammatory and vasoactive mediators are released including nitric oxide (NO), endothelins (ETs) and products of cyclo-oxygenase metabolism. It is probably the disordered production of these mediators in vascular beds that results in MODS. This review highlights recent research in this area with particular emphasis on possible therapeutic options.