Interferon and alternative activation of monocyte/macrophages in systemic sclerosis-associated pulmonary arterial hypertension

IL-13 receptor α2-arginase 2 pathway mediates IL-13-induced pulmonary hypertension

Although previous literature suggests that interleukin (IL)-13, a T-helper type 2 cell effector cytokine, might be involved in the pathogenesis of pulmonary hypertension (PH), direct proof is lacking. Furthermore, a potential mechanism underlying IL-13-induced PH has never been explored. This study's goal was to investigate the role and mechanism of IL-13 in the pathogenesis of PH. Lung-specific IL-13-overexpressing transgenic (Tg) mice were examined for hemodynamic changes and pulmonary vascular remodeling. IL-13 Tg mice spontaneously developed PH phenotype by the age of 2 mo with increased expression and activity of arginase 2 (Arg2). The role of Arg2 in the development of IL-13-stimulated PH was further investigated using Arg2 and IL-13 receptor α2 (Rα2) null mutant mice and the small-interfering RNA (siRNA)-silencing approach in vivo and in vitro, respectively. IL-13-stimulated medial thickening of pulmonary arteries and right ventricle systolic pressure were significantly decreased in the IL-13 Tg mice with Arg2 null mutation. On the other hand, the production of nitric oxide was further increased in the lungs of these mice. In our in vitro evaluations, the recombinant IL-13 treatment significantly enhanced the proliferation of human pulmonary artery smooth muscle cells in an Arg2-dependent manner. The IL-13-stimulated cellular proliferation and the expression of Arg2 in hpaSMC were markedly decreased with IL-13Rα2 siRNA silencing. Our studies demonstrate that IL-13 contributes to the development of PH via an IL-13Rα2-Arg2-dependent pathway. The intervention of this pathway could be a potential therapeutic target in pulmonary arterial hypertension.

Human pentraxin 3 (PTX3) as a novel biomarker for the diagnosis of pulmonary arterial hypertension

Background

Although inflammation is an important feature of pulmonary arterial hypertension (PAH), the usefulness of local inflammatory markers as biomarkers for PAH is unknown. In this study, we tested whether plasma concentrations of human pentraxin 3 (PTX3), a local inflammatory marker, would be a useful biomarker for detecting PAH.

Methods

Plasma PTX3 concentrations were evaluated in 50 PAH patients (27 with idiopathic PAH, 17 with PAH associated with connective tissue disease (CTD-PAH), and six with congenital heart disease), 100 age and sex-matched healthy controls, and 34 disease-matched CTD patients without PAH. Plasma concentrations of B-type natriuretic peptide (BNP) and C-reactive protein (CRP) were also determined.

Results

Mean PTX3 levels were significantly higher in all PAH patients than in the healthy controls (4.40±0.37 vs. 1.94±0.09 ng/mL, respectively; P<0.001). Using a threshold level of 2.84 ng/mL, PTX3 yielded a sensitivity of 74.0% and a specificity of 84.0% for the detection of PAH. In CTD-PAH patients, mean PTX3 concentrations were significantly higher than in CTD patients without PAH (5.02±0.69 vs. 2.40±0.14 ng/mL, respectively; P<0.001). There was no significant correlation between plasma levels of PTX3 and BNP or CRP. Receiver operating characteristic (ROC) curves for screening PAH in patients with CTD revealed that PTX3 (area under the ROC curve 0.866) is superior to BNP. Using a PTX3 threshold of 2.85 ng/mL maximized true-positive and false-negative results (sensitivity 94.1%, specificity 73.5%).

Conclusion

Plasma concentrations of PTX3 may be a better biomarker of PAH than BNP, especially in patients with CTD.

Diabetes-impaired wound healing and altered macrophage activation: a possible pathophysiologic correlation

Macrophages play a critical role in wound healing and can be activated to two distinctive phenotypes in vitro: classical macrophage activation (caM) and alternative macrophage activation (aaM). This study investigated whether the impaired cutaneous repair observed in streptozotocin-induced diabetic rats was associated with altered macrophage activation. Our results show that macrophage activation phenotypes could be observed in wound healing through double immunostaining. The caM macrophages appeared in the initial stage of wound healing, followed by aaM macrophages, which predominated in normal wounds. However, through examining markers associated with activation by immunoblotting and real-time polymerase chain reaction (PCR), diabetic wounds demonstrated insufficient caM in the early stage but excessive aaM in the later proliferative phase. Moreover, the macrophage activation markers were correlated with the instructive T helper cell type 1 (Th1)/Th2 cytokines in both groups. It was indicated that changed macrophage activation might contribute to impaired healing in diabetes wounds, and that strategies for reverting this abnormal activation could be useful for enhancing the wound healing process.

Erythroid-specific transcriptional changes in PBMCs from pulmonary hypertension patients

Background

Gene expression profiling of peripheral blood mononuclear cells (PBMCs) is a powerful tool for the identification of surrogate markers involved in disease processes. The hypothesis tested in this study was that chronic exposure of PBMCs to a hypertensive environment in remodeled pulmonary vessels would be reflected by specific transcriptional changes in these cells.

Methodology/Principal Findings

The transcript profiles of PBMCs from 30 idiopathic pulmonary arterial hypertension patients (IPAH), 19 patients with systemic sclerosis without pulmonary hypertension (SSc), 42 scleroderma-associated pulmonary arterial hypertensio patients (SSc-PAH), and 8 patients with SSc complicated by interstitial lung disease and pulmonary hypertension (SSc-PH-ILD) were compared to the gene expression profiles of PBMCs from 41 healthy individuals. Multiple gene expression signatures were identified which could distinguish various disease groups from controls. One of these signatures, specific for erythrocyte maturation, is enriched specifically in patients with PH. This association was validated in multiple published datasets. The erythropoiesis signature was strongly correlated with hemodynamic measures of increasing disease severity in IPAH patients. No significant correlation of the same type was noted for SSc-PAH patients, this despite a clear signature enrichment within this group overall. These findings suggest an association of the erythropoiesis signature in PBMCs from patients with PH with a variable presentation among different subtypes of disease.

Conclusions/Significance

In PH, the expansion of immature red blood cell precursors may constitute a response to the increasingly hypoxic conditions prevalent in this syndrome. A correlation of this erythrocyte signature with more severe hypertension cases may provide an important biomarker of disease progression.

An update on an immune system that goes awry in systemic sclerosis

PURPOSE OF REVIEW

This review aims to provide an overview of the recent data that emerged, further substantiating the critical role of innate immunity in systemic sclerosis (SSc).

RECENT FINDINGS

Driven by the evidence that newly identified SSc susceptibility genes are predominantly involved in immune regulation, we discuss the aberrant antigen presenting cell (APC) activation observed in the course of disease. In particular, we report the alternate activation of 'M1' and 'M2' macrophages reflecting different clinical phenotypes and the aberrant Toll-like receptor (TLR) response, whose effect on cytokine production is mostly evident in the early phases of disease; we especially highlight the increasing importance attributed to TLR3-mediated fibrosis. We next discuss the potential role for interferon (IFN) - producing plasmacytoid dendritic cells (pDCs) in triggering or perpetuating the inflammatory loop caused by TLR hyperactivation, possibly resulting in inflammasome-derived IL-1β-mediated fibrosis and IL-17 producing T helper cells (Th17) skewing.

SUMMARY

We propose to approach SSc as a multistep immune-mediated disease that is in need of a therapeutic strategy designed to interfere with one or more of these aberrant molecular pathways. Targeting of DCs could be such a target by which dampening the immune system could modify the course of SSc.

Pulmonary hypertension: screening and evaluation in scleroderma

PURPOSE OF REVIEW

The review provides an update of the epidemiology, pathogenesis, risk factors, screening and treatment of pulmonary arterial hypertension in systemic sclerosis.

RECENT FINDINGS

Several recent studies have investigated the utility of several noninvasive screening methods and the propagation of new treatments promise the clinician better outcomes than the current median survival time of 1 year for patients with scleroderma-related pulmonary arterial hypertension.

SUMMARY

Pulmonary hypertension is a frequent cause of morbidity and mortality in patients with systemic sclerosis. This review discusses the recent changes in the classification of pulmonary hypertension, especially the significance for the rheumatologist. A high clinical suspicion should be maintained, even in early scleroderma. Despite progress in echocardiography and biomarkers, right heart catheterization remains the only test that can diagnose pulmonary hypertension and differentiate pulmonary veno-occlusive disease from pulmonary arterial hypertension. The differentiation of these causes of pulmonary hypertension in the scleroderma patient is essential because the initiation of pulmonary vasodilators in veno-occlusive disease often leads to increased mortality. The role of screening with serum biomarkers and noninvasive testing remains controversial, and in this review we discuss the controversies and new recommendations in detail.

Basal Activation of Type I Interferons (Alpha2 and Beta) and 2'5'OAS Genes: Insights into Differential Expression Profiles of Interferon System Components in Systemic Sclerosis

Objective. Systemic sclerosis (SSc) is a complex autoimmune disease in which interferons (IFNs) may play an essential role. We hypothesized that type I and III IFNs may be found in increased levels in patients and be responsible for SSc autoimmune status. Methods. Type I and III IFN and ISG basal expression profiles were measured by qPCR using RNA from PBMCs of patients and controls . Results. Type I IFNs are increased in SSc patients, while no induction of type III IFNs was detected. This induction cannot be related to IRF7, since no upregulation of this gene was seen on patients. Of the ISGs tested, 2′5′OAS levels were increased in patients, while 6–16 and MxA levels were not. Conclusions. While there is no indication of type III IFN induction, increased levels of type I IFNs may lead to abnormal regulation of ISGs that can be responsible for immune system alterations described for SSc.