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

Serum biomarker for diagnostic evaluation of pulmonary arterial hypertension in systemic sclerosis

Background

Systemic sclerosis-associated pulmonary arterial hypertension (SSc-PAH) is one of the leading causes of death in SSc. Identification of a serum-based proteomic diagnostic biomarker for SSc-PAH would allow for rapid non-invasive screening and could positively impact patient survival. Identification and validation of novel proteins could potentially facilitate the identification of SSc-PAH, and might also point to important protein mediators in pathogenesis.

Methods

Thirteen treatment-naïve SSc-PAH patients had serum collected at time of diagnosis and were used as the discovery cohort for the protein-expression biomarker. Two proteins, Midkine and Follistatin-like 3 (FSTL3) were then validated by enzyme-linked immunosorbent assays. Midkine and FSTL3 were tested in combination to identify SSc-PAH and were validated in two independent cohorts of SSc-PAH (n = 23, n = 11).

Results

Eighty-two proteins were found to be differentially regulated in SSc-PAH sera. Two proteins (Midkine and FSTL3) were also shown to be elevated in publicly available data and their expression was evaluated in independent cohorts. In the validation cohorts, the combination of Midkine and FSTL3 had an area under the receiver operating characteristic curve (AUC) of 0.85 and 0.92 with respective corresponding measures of sensitivity of 76% and 91%, and specificity measures of 76% and 80%.

Conclusions

These findings indicate that there is a clear delineation between overall protein expression in sera from SSc patients and those with SSc-PAH. The combination of Midkine and FSTL3 can serve as an SSc-PAH biomarker and are potential drug targets for this rare disease population.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1679-8) contains supplementary material, which is available to authorized users.

Biomarkers for Pulmonary Vascular Remodeling in Systemic Sclerosis: A Pathophysiological Approach

Pulmonary arterial hypertension (PAH) is a severe complication of systemic sclerosis (SSc) associated with high morbidity and mortality. There are several biomarkers of SSc-PAH, reflecting endothelial physiology, inflammation, immune activation, extracellular matrix, metabolic changes, or cardiac involvement. Biomarkers associated with diagnosis, disease severity and progression have been identified, however, very few have been tested in a prospective setting. Some antinuclear antibodies such as nucleosome antibodies (NUC), anti-centromere antibodies (CENP-A/B) and anti-U3-ribonucleoprotein (anti-U3-RNP) are associated with PAH while anti-U1-ribonucleoprotein (anti-U1-RNP) is associated with a reduced PAH risk. Anti-endothelin receptor and angiotensin-1 receptor antibodies might be good markers of SSc-PAH and progression of pulmonary vasculopathy. Regarding the markers reflecting immune activation and inflammation, there are many inconsistent results. CXCL-4 was associated with SSc progression including PAH and lung fibrosis. Growth differentiation factor (GDF)-15 was associated with PAH and mortality but is not specific for SSc. Among the metabolites, kynurenine was identified as diagnostic marker for PAH, however, its pathologic role in the disease is unclear. Endostatin, an angiostatic factor, was associated with heart failure and poor prognosis. Established heart related markers, such as N-terminal fragment of A-type natriuretic peptide/brain natriuretic peptide (NT-proANP, NT-proBNP) or troponin I/T are elevated in SSc-PAH but are not specific for the right ventricle and may be increased to the same extent in left heart disease. Taken together, there is no universal specific biomarker for SSc-PAH, however, there is a pattern of markers that is strongly associated with a risk of vascular complications in SSc patients. Further comprehensive, multicenter and prospective studies are warranted to develop reliable algorithms for detection and prognosis of SSc-PAH.

Diesel exhaust inhalation exposure induces pulmonary arterial hypertension in mice

Diesel exhaust (DE) is one of the main sources of urban air pollution. An increasing number of evidence showed the association of air pollution with cardiovascular diseases. Pulmonary arterial hypertension (PAH) is one of the most disastrous vascular diseases, which results in right ventricular failure and death. However, the relationship of DE inhalation exposure with PAH is still unknown. In this study, male adult mice were exposed by inhalation to filtered ambient air (negative control), 10% O₂ hypoxia (PAH-phenotype positive control), 350 μg/m³ particulate matter whole DE, or the combination of DE and hypoxic condition. DE inhalation induced PAH-phenotype accompanied with increased right ventricular systolic pressure (RVSP), right ventricle hypertrophy and pulmonary arterial thickening in a mouse model. DE exposure induced the proliferation of vascular smooth muscle cells (VSMCs) and apoptosis of endothelial cells in pulmonary artery. DE inhalation exposure induced an accumulation of CD45⁺ lymphocytes and CD68⁺ macrophages surrounding and infiltrating pulmonary arteriole. The levels of pro-inflammatory cytokines tumor necrosis factor (TNF-α), interleukin-6 (IL-6) and IL-13 produced by T helper 17 (Th17) and Th2 cells were markedly elevated in lung tissues of mice after DE inhalation exposure. Our findings suggest DE exposure induces PAH by activating Th17-skewed and Th2-droved responses, stimulating VSMCs proliferation and inducing endothelial cell apoptosis by the production of multifunctional pro-inflammatory cytokines, especially IL-6 and TNF-α. Considering the adverse impact of air pollution on health care, it is imperative to understand air pollution-induced susceptibility of progressive cardiopulmonary disease, such as PAH, and also elucidate critical mechanistic pathways which mediate pulmonary artery vascular remodeling and may serve as targets for preventive measures.

Patients with systemic sclerosis-associated pulmonary arterial hypertension express a genomic signature distinct from patients with interstitial lung disease

Objective

Pulmonary arterial hypertension (PAH) and interstitial lung disease (ILD) are major causes of mortality in systemic sclerosis (SSc). We used a previously identified microarray biomarker to determine if SSc-PAH and SSc-ILD patients demonstrate distinct gene expression profiles.

Methods

PBMCs were collected from healthy controls (n=10), SSc (SSc) patients without pulmonary hypertension [SSc-noPAH, n=39], and SSc-PAH patients (n=21; mPAP≥25, PCWP≤15, PVR≥3WU) diagnosed by right heart catheterization (RHC). SSc-ILD patients were defined as those with evidence of fibrosis on chest CT and significant restriction (FVC<70% predicted, n = 11). SSc-PAH biomarker included 69 genes selected by unbiased statistical screening of 3 publicly available microarray studies. RNA levels were measured by Nanostring. Gene expression levels that were significantly correlated with PAH (multiple statistical measures) were chosen as inputs into a forward selection logistic regression model.

Results

When ILD patients were included (n=64), 4 genes (S100P, CD8B1, CCL2, TIMP1) and male sex predicted PAH with a high level of accuracy (AUC = 0.83). Without ILD patients (n=53), 2 genes (THBS1, CD8B1) and male sex predicted PAH with a high level of accuracy (AUC = 0.80). When examining SSc patients with borderline elevated pulmonary pressures (mPAP = 21-24 mmHg), gene expression changes closely resembled the SSc-PAH group, except for THBS1.

Conclusion

SSc-PAH and SSc-ILD have similar, but distinct, gene expression profiles. Many gene expression changes occur early in the disease course, potentially allowing for early detection. THBS1 appears to be an important mediator in the development of PAH-predominant phenotype. Further prospective investigation is warranted.

Distinct Properties of Human M-CSF and GM-CSF Monocyte-Derived Macrophages to Simulate Pathological Lung Conditions In Vitro: Application to Systemic and Inflammatory Disorders with Pulmonary Involvement

Macrophages play a central role in the pathogenesis of inflammatory and fibrotic lung diseases. However, alveolar macrophages (AM) are poorly available in humans to perform in vitro studies due to a limited access to broncho-alveolar lavage (BAL). In this study, to identify the best alternative in vitro model for human AM, we compared the phenotype of AM obtained from BAL of patients suffering from three lung diseases (lung cancers, sarcoidosis and Systemic Sclerosis (SSc)-associated interstitial lung disease) to human blood monocyte-derived macrophages (MDMs) differentiated with M-CSF or GM-CSF. The expression of eight membrane markers was evaluated by flow cytometry. Globally, AM phenotype was closer to GM-CSF MDMs. However, the expression levels of CD163, CD169, CD204, CD64 and CD36 were significantly higher in SSc-ILD than in lung cancers. Considering the expression of CD204 and CD36, the phenotype of SSc-AM was closer to MDMs, from healthy donors or SSc patients, differentiated by M-CSF rather than GM-CSF. The comparative secretion of IL-6 by SSc-MDMs and SSc-AM is concordant with these phenotypic considerations. Altogether, these results support the M-CSF MDM model as a relevant in vitro alternative to simulate AM in fibrotic disorders such as SSc.

JAK2 mediates lung fibrosis, pulmonary vascular remodelling and hypertension in idiopathic pulmonary fibrosis: an experimental study

BACKGROUND

Pulmonary hypertension (PH) is a common disorder in patients with idiopathic pulmonary fibrosis (IPF) and portends a poor prognosis. Recent studies using vasodilators approved for PH have failed in improving IPF mainly due to ventilation (V)/perfusion (Q) mismatching and oxygen desaturation. Janus kinase type 2 (JAK2) is a non-receptor tyrosine kinase activated by a broad spectrum of profibrotic and vasoactive mediators, but its role in PH associated to PH is unknown.

OBJECTIVE

The study of JAK2 as potential target to treat PH in IPF.

METHODS AND RESULTS

JAK2 expression was increased in pulmonary arteries (PAs) from IPF (n=10; 1.93-fold; P=0.0011) and IPF+PH (n=9; 2.65-fold; P<0.0001) compared with PA from control subjects (n=10). PA remodelling was evaluated in human pulmonary artery endothelial cells (HPAECs) and human pulmonary artery smooth muscle cells (HPASMCs) from patients with IPF in vitro treated with the JAK2 inhibitor JSI-124 or siRNA-JAK2 and stimulated with transforming growth factor beta. Both JSI-124 and siRNA-JAK2 inhibited the HPAEC to mesenchymal transition and the HPASMCs to myofibroblast transition and proliferation. JAK2 inhibition induced small PA relaxation in precision-cut lung slice experiments. PA relaxation was dependent of the large conductance calcium-activated potassium channel (BK_Ca). JAK2 inhibition activated BK_Ca channels and reduced intracellular Ca²⁺. JSI-124 1 mg/kg/day, reduced bleomycin-induced lung fibrosis, PA remodelling, right ventricular hypertrophy, PA hypertension and V/Q mismatching in rats. The animal studies followed the ARRIVE guidelines.

CONCLUSIONS

JAK2 participates in PA remodelling and tension and may be an attractive target to treat IPF associated to PH.

Mycophenolate Mofetil Treatment of Systemic Sclerosis Reduces Myeloid Cell Numbers and Attenuates the Inflammatory Gene Signature in Skin

Fewer than half of patients with systemic sclerosis demonstrate modified Rodnan skin score improvement during mycophenolate mofetil (MMF) treatment. To understand the molecular basis for this observation, we extended our prior studies and characterized molecular and cellular changes in skin biopsies from subjects with systemic sclerosis treated with MMF. Eleven subjects completed ≥24 months of MMF therapy. Two distinct skin gene expression trajectories were observed across six of these subjects. Three of the six subjects showed attenuation of the inflammatory signature by 24 months, paralleling reductions in CCL2 mRNA expression in skin and reduced numbers of macrophages and myeloid dendritic cells in skin biopsies. MMF cessation at 24 months resulted in an increased inflammatory score, increased CCL2 mRNA and protein levels, modified Rodnan skin score rebound, and increased numbers of skin myeloid cells in these subjects. In contrast, three other subjects remained on MMF >24 months and showed a persistent decrease in inflammatory score, decreasing or stable modified Rodnan skin score, CCL2 mRNA reductions, sera CCL2 protein levels trending downward, reduction in monocyte migration, and no increase in skin myeloid cell numbers. These data summarize molecular changes during MMF therapy that suggest reduction of innate immune cell numbers, possibly by attenuating expression of chemokines, including CCL2.

Sialic Acid-Binding Immunoglobulin-Like Lectin1 as a Novel Predictive Biomarker for Relapse in Graves' Disease: A Multicenter Study

BACKGROUND

There are currently no reliable biomarkers to predict relapse in Graves' disease (GD). In the present study, we investigated novel diagnostic biomarkers to predict the long-term remission of or relapse in GD.

METHODS

A DNA microarray analysis was performed to examine gene expression in the peripheral leukocytes of a frequently relapsing patient with GD and a patient in long-term remission after the discontinuation of antithyroid drugs (ATDs). Based on the DNA microarray analysis, we focused on Sialic acid-binding immunoglobulin-like lectin1 (SIGLEC1) as a candidate novel biomarker to predict GD relapse. Three hundred and fifty-eight patients with GD in the thyroid clinics of four different hospitals in Japan were included in a cross-sectional study to establish whether SIGLEC1 mRNA levels distinguish GD relapse experience from long-term remission. An additional 55 patients with GD were enrolled in a prospective study to clarify whether SIGLEC1 mRNA levels at ATD discontinuation predict GD relapse.

RESULTS

SIGLEC1 mRNA levels were significantly higher in patients with GD relapse experience than in those in long-term remission. Based on the receiver operating characteristic analysis, we found that high SIGLEC1 mRNA levels (≥258.9 copies) significantly distinguished GD relapse experience from long-term remission (p < 0.0001; sensitivity 66.7%, specificity 70.1%). In the prospective study, when the optimal cutoff value from the receiver operating characteristic curve analysis was applied to SIGLEC1 mRNA positivity at ATD discontinuation, SIGLEC1-positive patients (≥258.9 copies) showed a significantly higher cumulative risk of relapse than SIGLEC1-negative patients (<258.9 copies) (p = 0.022, the log-rank test).

CONCLUSIONS

SIGLEC1 mRNA levels have potential as a novel predictive biomarker for GD relapse.

Immune cells and autoantibodies in pulmonary arterial hypertension

Analyses of immunity in pulmonary arterial hypertension (PAH) support the notion that maladaptation of the immune response exists. Altered immunity is an increasingly recognized feature of PAH. Indeed, a delicate balance between immunity and tolerance exists and any disturbance may result in chronic inflammation or autoimmunity. This is suggested by infiltration of various immune cells (e.g. macrophages, T and B lymphocytes) in remodeled pulmonary vessels. In addition, several types of autoantibodies directed against antinuclear antigens, endothelial cells (ECs) and fibroblasts have been found in idiopathic and systemic sclerosis-associated PAH. These autoantibodies may play an important role in EC apoptosis and in the expression of cell adhesion molecules. This review article provides an overview of immunity pathways highlighting their potential roles in pulmonary vascular remodeling in PAH and the possibility of future targeted therapy.

Dendritic cells in systemic sclerosis: Advances from human and mice studies

Systemic sclerosis (SSc) is a complex heterogeneous fibrotic autoimmune disease with an unknown exact etiology, and characterized by three hallmarks: fibrosis, vasculopathy, and immune dysfunction. Dendritic cells (DCs) are specialized cells in pathogen sensing with high potency of antigen presentation and capable of releasing mediators to shape the immune response. Altered DCs distributions and their impaired functions may account for their role in breaking the immune tolerance and driving inflammation in SSc, and the direct contribution of DCs in promoting endothelial dysfunction and fibrotic process has only begun to be understood. Plasmacytoid dendritic cells in particular have been implicated due to their high production of type I interferon as well as other cytokines and chemokines, including the pro-inflammatory and anti-angiogenic CXCL4. Furthermore, a deeper understanding of human and mouse DC biology has clarified their identification and function in different tissues, and novel DC subsets have only recently been discovered. In this review, we highlight key findings and recent advances exploring DC role in the pathogenesis of SSc and other related autoimmune diseases, and consideration of their potential use as targeted therapy in SSc.

Endogenous ligands of TLR4 promote unresolving tissue fibrosis: Implications for systemic sclerosis and its targeted therapy

Fibrosis, the hallmark of scleroderma or systemic sclerosis (SSc), is a complex, dynamic and generally irreversible pathophysiological process that leads to tissue disruption, and lacks effective therapy. While early-stage fibrosis resembles normal wound healing, in SSc fibrosis fails to resolve. Innate immune signaling via toll-like receptors (TLRs) has recently emerged as a key driver of persistent fibrotic response in SSc. Recurrent injury in genetically predisposed individual causes generation of "damage-associated molecular patterns" (DAMPs) such as fibronectin-EDA and tenascin-C. Sensing of these danger signals by TLR4 on resident cells elicits potent stimulatory effects on fibrotic gene expression and myofibroblast differentiation, and appears to sensitize fibroblasts to the profibrotic stimulatory effect of TGF-β. Thus, DAMPs induce TLR4-mediated innate immune signaling on resident mesenchymal cells which drives the emergence and persistence of fibrotic cells in tissues, and underlies the switch from a self-limited repair response to non-resolving pathological fibrosis characteristic of SSc. In this review, we present current views of the DAMP-TLR4 axis in driving sustained fibroblasts activation and its pathogenic roles in fibrosis progression in SSc, and potential anti-fibrotic approaches for selective therapeutic targeting of TLR4 signaling.

Synergistic Role of Endothelial ERG and FLI1 in Mediating Pulmonary Vascular Homeostasis

Endothelial cell (EC) activation underlies many vascular diseases, including pulmonary arterial hypertension (PAH). Several members of the E-twenty six (ETS) family of transcription factors are important regulators of the gene network governing endothelial homeostasis, and their aberrant expression is associated with pathological angiogenesis. The goal of this study was to determine whether deficiencies of the ETS family member, Friend leukemia integration 1 transcription factor (FLI1), and its closest homolog, ETS-related gene (ERG), are associated with PAH. We found that endothelial ERG was significantly reduced in the lung samples from patients with PAH, as well as in chronically hypoxic mice. Functional studies revealed that depletion of ERG or FLI1 in human pulmonary ECs led to increased expression of inflammatory genes, including IFN genes, whereas genes regulating endothelial homeostasis and cell-cell adhesion were down-regulated. Simultaneous knockdown of both ERG and FLI1 had synergistic or additive effects on the expression of these genes, suggesting that ERG and FLI1 coregulate at least a subset of their target genes. Functionally, knockdown of ERG and FLI1 induced cell monolayer permeability with a potency similar to that of vascular endothelial growth factor. Notably, stimulation of ECs with Toll-like receptor 3 ligand poly(I:C) suppressed ERG expression and induced ERG dissociation from the IFNB1 promoter, while promoting signal transducers and activators of transcription 1 (STAT1) recruitment. Consistent with the up-regulation of inflammatory genes seen in vitro, Erg and Fli1 double-heterozygote mice showed increased immune cell infiltration and expression of cytokines in the lung. In conclusion, loss of ERG and FLI1 might contribute to the pathogenesis of vascular lung complications through the induction of inflammation.

A Time- and Compartment-Specific Activation of Lung Macrophages in Hypoxic Pulmonary Hypertension

Studies in various animal models suggest an important role for pulmonary macrophages in the pathogenesis of pulmonary hypertension (PH). Yet, the molecular mechanisms characterizing the functional macrophage phenotype relative to time and pulmonary localization and compartmentalization remain largely unknown. In this study, we used a hypoxic murine model of PH in combination with FACS to quantify and isolate lung macrophages from two compartments over time and characterize their programing via RNA sequencing approaches. In response to hypoxia, we found an early increase in macrophage number that was restricted to the interstitial/perivascular compartment, without recruitment of macrophages to the alveolar compartment or changes in the number of resident alveolar macrophages. Principal component analysis demonstrated significant differences in overall gene expression between alveolar and interstitial macrophages (IMs) at baseline and after 4 and 14 d hypoxic exposure. Alveolar macrophages at both day 4 and 14 and IMs at day 4 shared a conserved hypoxia program characterized by mitochondrial dysfunction, proinflammatory gene activation, and mTORC1 signaling, whereas IMs at day 14 demonstrated a unique anti-inflammatory/proreparative programming state. We conclude that the pathogenesis of vascular remodeling in hypoxic PH involves an early compartment-independent activation of lung macrophages toward a conserved hypoxia program, with the development of compartment-specific programs later in the course of the disease. Thus, harnessing time- and compartment-specific differences in lung macrophage polarization needs to be considered in the therapeutic targeting of macrophages in hypoxic PH and potentially other inflammatory lung diseases.

A novel multi-network approach reveals tissue-specific cellular modulators of fibrosis in systemic sclerosis

Background

Systemic sclerosis (SSc) is a multi-organ autoimmune disease characterized by skin fibrosis. Internal organ involvement is heterogeneous. It is unknown whether disease mechanisms are common across all involved affected tissues or if each manifestation has a distinct underlying pathology.

Methods

We used consensus clustering to compare gene expression profiles of biopsies from four SSc-affected tissues (skin, lung, esophagus, and peripheral blood) from patients with SSc, and the related conditions pulmonary fibrosis (PF) and pulmonary arterial hypertension, and derived a consensus disease-associate signature across all tissues. We used this signature to query tissue-specific functional genomic networks. We performed novel network analyses to contrast the skin and lung microenvironments and to assess the functional role of the inflammatory and fibrotic genes in each organ. Lastly, we tested the expression of macrophage activation state-associated gene sets for enrichment in skin and lung using a Wilcoxon rank sum test.

Results

We identified a common pathogenic gene expression signature—an immune–fibrotic axis—indicative of pro-fibrotic macrophages (MØs) in multiple tissues (skin, lung, esophagus, and peripheral blood mononuclear cells) affected by SSc. While the co-expression of these genes is common to all tissues, the functional consequences of this upregulation differ by organ. We used this disease-associated signature to query tissue-specific functional genomic networks to identify common and tissue-specific pathologies of SSc and related conditions. In contrast to skin, in the lung-specific functional network we identify a distinct lung-resident MØ signature associated with lipid stimulation and alternative activation. In keeping with our network results, we find distinct MØ alternative activation transcriptional programs in SSc-associated PF lung and in the skin of patients with an “inflammatory” SSc gene expression signature.

Conclusions

Our results suggest that the innate immune system is central to SSc disease processes but that subtle distinctions exist between tissues. Our approach provides a framework for examining molecular signatures of disease in fibrosis and autoimmune diseases and for leveraging publicly available data to understand common and tissue-specific disease processes in complex human diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-017-0417-1) contains supplementary material, which is available to authorized users.

Pulmonary extra-medullary hematopoiesis and pulmonary hypertension from underlying polycythemia vera: a case series

Myeloproliferative neoplasia (MPN)-associated pulmonary hypertension (PH) is included in group five of the most recent clinical classification of PH.¹ The MPNs are a heterogeneous group of disorders that includes disorders with primary expression of a myeloid phenotype and disorders characterized by expression of the Janus Kinase 2 (JAK2) mutation, p.V617F. The latter includes essential thrombocytosis, polycythemia vera, and idiopathic myelofibrosis.² Pulmonary extra-medullary hematopoiesis (EMH) refers to the presence of hematopoietic precursor cells in the lung. It is a rare complication associated with myelofibrosis. Here we present a case series highlighting the clinical–pathological–radiological features of pulmonary EMH and PH from underlying polycythemia vera.

Epstein-Barr virus lytic infection promotes activation of Toll-like receptor 8 innate immune response in systemic sclerosis monocytes

Background

Monocytes/macrophages are activated in several autoimmune diseases, including systemic sclerosis (scleroderma; SSc), with increased expression of interferon (IFN)-regulatory genes and inflammatory cytokines, suggesting dysregulation of the innate immune response in autoimmunity. In this study, we investigated whether the lytic form of Epstein-Barr virus (EBV) infection (infectious EBV) is present in scleroderma monocytes and contributes to their activation in SSc.

Methods

Monocytes were isolated from peripheral blood mononuclear cells (PBMCs) depleted of the CD19+ cell fraction, using CD14/CD16 negative-depletion. Circulating monocytes from SSc and healthy donors (HDs) were infected with EBV. Gene expression of innate immune mediators were evaluated in EBV-infected monocytes from SSc and HDs. Involvement of Toll-like receptor (TLR)8 in viral-mediated TLR8 response was investigated by comparing the TLR8 expression induced by infectious EBV to the expression stimulated by CL075/TLR8/agonist-ligand in the presence of TLR8 inhibitor in THP-1 cells.

Results

Infectious EBV strongly induced TLR8 expression in infected SSc and HD monocytes in vitro. Markers of activated monocytes, such as IFN-regulated genes and chemokines, were upregulated in SSc- and HD-EBV-infected monocytes. Inhibiting TLR8 expression reduced virally induced TLR8 in THP-1 infected cells, demonstrating that innate immune activation by infectious EBV is partially dependent on TLR8. Viral mRNA and proteins were detected in freshly isolated SSc monocytes. Microarray analysis substantiated the evidence of an increased IFN signature and altered level of TLR8 expression in SSc monocytes carrying infectious EBV compared to HD monocytes.

Conclusion

This study provides the first evidence of infectious EBV in monocytes from patients with SSc and links EBV to the activation of TLR8 and IFN innate immune response in freshly isolated SSc monocytes. This study provides the first evidence of EBV replication activating the TLR8 molecular pathway in primary monocytes. Immunogenicity of infectious EBV suggests a novel mechanism mediating monocyte inflammation in SSc, by which EBV triggers the innate immune response in infected cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1237-9) contains supplementary material, which is available to authorized users.

Alternatively Activated (M2) Macrophage Phenotype Is Inducible by Endothelin-1 in Cultured Human Macrophages

Background

Alternatively activated (M2) macrophages are phenotypically characterized by the expression of specific markers, mainly macrophage scavenger receptors (CD204 and CD163) and mannose receptor-1 (CD206), and participate in the fibrotic process by over-producing pro-fibrotic molecules, such as transforming growth factor-beta1 (TGFbeta1) and metalloproteinase (MMP)-9. Endothelin-1 (ET-1) is implicated in the fibrotic process, exerting its pro-fibrotic effects through the interaction with its receptors (ET_A and ET_B). The study investigated the possible role of ET-1 in inducing the transition from cultured human macrophages into M2 cells.

Methods

Cultured human monocytes (THP-1 cell line) were activated into macrophages (M0 macrophages) with phorbol myristate acetate and subsequently maintained in growth medium (M0-controls) or treated with either ET-1 (100nM) or interleukin-4 (IL-4, 10ng/mL, M2 inducer) for 72 hours. Similarly, primary cultures of human peripheral blood monocyte (PBM)-derived macrophages obtained from healthy subjects, were maintained in growth medium (untreated cells) or treated with ET-1 or IL-4 for 6 days. Both M0 and PBM-derived macrophages were pre-treated with ET receptor antagonist (ET_A/BRA, bosentan 10^-5M) for 1 hour before ET-1 stimulation. Protein and gene expression of CD204, CD206, CD163, TGFbeta1 were analysed by immunocytochemistry, Western blotting and quantitative real time polymerase chain reaction (qRT-PCR). Gene expression of interleukin(IL)-10 and macrophage derived chemokine (CCL-22) was evaluated by qRT-PCR. MMP-9 production was investigated by gel zymography.

Results

ET-1 significantly increased the expression of M2 phenotype markers CD204, CD206, CD163, IL-10 and CCL-22, and the production of MMP-9 in both cultures of M0 and PBM-derived macrophages compared to M0-controls and untreated cells. In cultured PBM-derived macrophages, ET-1 increased TGFbeta1 protein and gene expression compared to untreated cells. The ET-1-mediated effects were contrasted by ET_A/BRA treatment in both cultured cell types.

Conclusion

ET-1 seems to induce the M2 phenotype in cultured human macrophages, a process apparently contrasted by the action of the ET_A/BRA, suggesting possible clinical implications in those fibrotic diseases characterized by increased ET-1 concentrations, such as systemic sclerosis but also type 2 diabetes.

Dendritic cells maintain dermal adipose-derived stromal cells in skin fibrosis

Scleroderma is a group of skin-fibrosing diseases for which there are no effective treatments. A feature of the skin fibrosis typical of scleroderma is atrophy of the dermal white adipose tissue (DWAT). Adipose tissue contains adipose-derived mesenchymal stromal cells (ADSCs) that have regenerative and reparative functions; however, whether DWAT atrophy in fibrosis is accompanied by ADSC loss is poorly understood, as are the mechanisms that might maintain ADSC survival in fibrotic skin. Here, we have shown that DWAT ADSC numbers were reduced, likely because of cell death, in 2 murine models of scleroderma skin fibrosis. The remaining ADSCs showed a partial dependence on dendritic cells (DCs) for survival. Lymphotoxin β (LTβ) expression in DCs maintained ADSC survival in fibrotic skin by activating an LTβ receptor/β1 integrin (LTβR/β1 integrin) pathway on ADSCs. Stimulation of LTβR augmented the engraftment of therapeutically injected ADSCs, which was associated with reductions in skin fibrosis and improved skin function. These findings provide insight into the effects of skin fibrosis on DWAT ADSCs, identify a DC-ADSC survival axis in fibrotic skin, and suggest an approach for improving mesenchymal stromal cell therapy in scleroderma and other diseases.

Fresh Insights into Disease Etiology and the Role of Microbial Pathogens

Pathogens have been implicated in the initiation and/or promotion of systemic sclerosis (scleroderma, SSc); however, no evidence was found to substantiate the direct contribution to this disease in past years. Recently, significant advances have been made in understanding the role of the innate immune system in SSc pathogenesis, supporting the idea that pathogens might interact with host innate immune-regulatory responses in SSc. In light of these findings, we review the studies that identified the presence of pathogens in SSc, along with studies on pathogens implicated in driving the innate immune dysregulation in SSc. The goal of this review is to illustrate how these pathogens, specifically viruses, may play important role both as triggers of the innate immune system, and critical players in the development of SSc disease.

Aberrant immune response with consequent vascular and connective tissue remodeling - causal to scleroderma and associated syndromes such as Raynaud phenomenon and other fibrosing syndromes?

PURPOSE OF REVIEW

Scleroderma and other autoimmune-induced connective tissue diseases are characterized by dysfunctions in the immune system, connective tissue and the vasculature. We are focusing on systemic sclerosis (SSc)-associated pulmonary hypertension, which remains a leading cause of death with only a 50-60% of 2-year survival rate.

RECENT FINDINGS

Much research and translational efforts have been directed at understanding the immune response that causes SSc and the networked interactions with the connective tissue and the vasculature. One of the unexpected findings was that in some cases the pathogenic immune response in SSc resembles the immune response to helminth parasites. During coevolution, means of communication were developed which protect the host from over-colonization with parasites and which protect the parasite from excessive host responses. One explanation for the geographically clustered occurrence of SSc is that environmental exposures combined with genetic predisposition turn on triggers of molecular and cellular modules that were once initiated by parasites.

SUMMARY

Future research is needed to further understand the parasite-derived signals that dampen the host response. Therapeutic helminth infection or treatment with parasite-derived response modifiers could be promising new management tools for autoimmune connective tissue diseases.

miR-155 in the progression of lung fibrosis in systemic sclerosis

BACKGROUND

MicroRNA (miRNA) control key elements of mRNA stability and likely contribute to the dysregulated lung gene expression observed in systemic sclerosis associated interstitial lung disease (SSc-ILD). We analyzed the miRNA gene expression of tissue and cells from patients with SSc-ILD. A chronic lung fibrotic murine model was used.

METHODS

RNA was isolated from lung tissue of 12 patients with SSc-ILD and 5 controls. High-resolution computed tomography (HRCT) was performed at baseline and 2-3 years after treatment. Lung fibroblasts and peripheral blood mononuclear cells (PBMC) were isolated from healthy controls and patients with SSc-ILD. miRNA and mRNA were analyzed by microarray, quantitative polymerase chain reaction, and/or Nanostring; pathway analysis was performed by DNA Intelligent Analysis (DIANA)-miRPath v2.0 software. Wild-type and miR-155 deficient (miR-155ko) mice were exposed to bleomycin.

RESULTS

Lung miRNA microarray data distinguished patients with SSc-ILD from healthy controls with 185 miRNA differentially expressed (q < 0.25). DIANA-miRPath revealed 57 Kyoto Encyclopedia of Genes and Genomes pathways related to the most dysregulated miRNA. miR-155 and miR-143 were strongly correlated with progression of the HRCT score. Lung fibroblasts only mildly expressed miR-155/miR-21 after several stimuli. miR-155 PBMC expression strongly correlated with lung function tests in SSc-ILD. miR-155ko mice developed milder lung fibrosis, survived longer, and weaker lung induction of several genes after bleomycin exposure compared to wild-type mice.

CONCLUSIONS

miRNA are dysregulated in the lungs and PBMC of patients with SSc-ILD. Based on mRNA-miRNA interaction analysis and pathway tools, miRNA may play a role in the progression of the disease. Our findings suggest that targeting miR-155 might provide a novel therapeutic strategy for SSc-ILD.

Challenges and Current Efforts in the Development of Biomarkers for Chronic Inflammatory and Remodeling Conditions of the Lungs

This review discusses biomarkers that are being researched for their usefulness to phenotype chronic inflammatory lung diseases that cause remodeling of the lung's architecture. The review focuses on asthma, chronic obstructive pulmonary disease (COPD), and pulmonary hypertension. Bio-markers of environmental exposure and specific classes of biomarkers (noncoding RNA, metabolism, vitamin, coagulation, and microbiome related) are also discussed. Examples of biomarkers that are in clinical use, biomarkers that are under development, and biomarkers that are still in the research phase are discussed. We chose to present examples of the research in biomarker development by diseases, because asthma, COPD, and pulmonary hypertension are distinct entities, although they clearly share processes of inflammation and remodeling.

Dissecting the heterogeneity of skin gene expression patterns in systemic sclerosis

OBJECTIVE

To examine the heterogeneity of global transcriptome patterns in systemic sclerosis (SSc) skin in a large sample of patients with SSc and control subjects.

METHODS

Skin biopsy specimens obtained from 61 patients enrolled in the Genetics versus Environment in Scleroderma Outcome Study (GENISOS) cohort and 36 unaffected control subjects with a similar demographic background were examined by Illumina HumanHT-12 bead arrays. Followup experiments using quantitative polymerase chain reaction and immunohistochemical analysis were also performed.

RESULTS

We identified 2,754 differentially expressed transcripts in SSc patients compared with controls. Clustering analysis revealed 2 prominent transcriptomes in SSc patients: the keratin and fibroinflammatory signatures. Higher keratin transcript scores were associated with shorter disease duration and interstitial lung disease, while higher fibroinflammatory scores were associated with diffuse cutaneous involvement, a higher skin score at the biopsy site, and a higher modified Rodnan skin thickness score. A subgroup of patients with significantly longer disease duration had a normal-like transcript pattern. Analysis of cell type-specific signature scores revealed remarkable heterogeneity across patients. Significantly higher scores were calculated for fibroblasts (72% of patients), microvascular cells (61%), macrophages (54%), and dendritic cells (DCs) (49%). The majority of samples with significantly higher fibroblast scores (35 of 44 [80%]) had significantly increased macrophage and/or DC scores. Further analysis and immunohistochemical staining indicated that the keratin signature was not a general marker of keratinocyte activation but was in fact associated with an activation pattern in hair and adnexal structures.

CONCLUSION

Prominent fibroinflammatory and keratin signatures are present in SSc skin. Expression profiles of SSc skin show significant heterogeneity, and this finding might be useful for stratifying patients for targeted therapies or predicting the response to immunosuppression.

The HLA-B*35 allele modulates ER stress, inflammation and proliferation in PBMCs from Limited Cutaneous Systemic Sclerosis patients

Introduction

HLA-B*35 is associated with increased risk of developing pulmonary hypertension in SSc patients. We previously reported that HLA-B*35 induces endothelial cell dysfunction via activation of ER stress/UPR and upregulation of the inflammatory response. Because PBMCs from lcSSc-PAH patients are also characterized by activation of ER stress/UPR and inflammation, the goal of this study was to assess whether the presence of HLA-B*35 contributes to those characteristics.

Methods

PBMCs were purified from healthy controls (n = 49 HC) and lcSSc patients, (n = 44 with PAH, n = 53 without PAH). PBMCs from each group were stratified for the presence of HLA-B*35. Global changes in gene expression in response to HLA-B*35, HLA-B*8 or empty lentivirus were investigated by microarray analysis in HC PBMCs. Total RNA was extracted and qPCR was performed to measure gene expression.

Results

ER stress markers, in particular the chaperones BiP and DNAJB1 were significantly elevated in PBMC samples carrying the HLA-B*35 allele. IL-6 expression was also significantly increased in HLA-B*35 lcSSc PBMCs and positively correlated with ER stress markers. Likewise, HMGB1 was increased in HLA-B*35-positive lcSSc PBMCs. Global gene expression analysis was used to further probe the role of HLA-B*35. Among genes downregulated by HLA-B*35 lentivirus were genes related to complement (C1QB, C1QC), cell cycle (CDNK1A) and apoptosis (Bax, Gadd45). Interestingly, complement genes (C1QC and C1QB) showed elevated expression in lcSSc without PAH, but were expressed at the low levels in lcSSc-PAH. The presence of HLA-B*35 correlated with the decreased expression of the complement genes. Furthermore, HLA-B*35 correlated with decreased expression of cyclin inhibitors (p21, p57) and pro-apoptotic genes (Bax, Gadd45) in lcSSc B35 subjects. FYN, a tyrosine kinase involved in proliferation of immune cells, was among the genes that were positively regulated by HLA-B*35. HLA-B*35 correlated with increased levels of FYN in lcSSc PBMCs.

Conclusions

Our study demonstrates that HLA-B*35 contributes to the dysregulated expression of selected ER stress, inflammation and proliferation related genes in lcSSc patient PBMCs, as well as healthy individuals, thus supporting a pathogenic role of HLA-B*35 in the development of PAH in SSc patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0881-1) contains supplementary material, which is available to authorized users.

Update on macrophages and innate immunity in scleroderma

PURPOSE OF REVIEW

In this review of the literature from 2014 through mid-2015, we examine new data that shed light on how macrophages and other innate immune cells and signals contribute to inflammation, vascular dysfunction, and fibrosis in scleroderma.

RECENT FINDINGS

Recent human studies have focused on changes early in scleroderma, and linked macrophages to inflammation in skin and progression of lung disease. Plasmacytoid dendritic cells have been implicated in vascular dysfunction. In mice, several factors have been identified that influence macrophage activation and experimental fibrosis. However, emerging data also suggest that myeloid cells can have differential effects in fibrosis. Sustained signaling through different toll-like receptors can lead to inflammation or fibrosis, and these signals can influence both immune and nonimmune cells.

SUMMARY

There are many types of innate immune cells that can potentially contribute to scleroderma and will be worth exploring in detail. Experimentally dissecting the roles of macrophages based on ontogeny and activation state, and the innate signaling pathways in the tissue microenvironment, may also lead to better understanding of scleroderma pathogenesis.

Gene expression profiling offers insights into the role of innate immune signaling in SSc

Systemic sclerosis (SSc) is characterized by inflammation, vascular dysfunction, and ultimately fibrosis. Progress in understanding disease pathogenesis and developing effective disease treatments has been hampered by an incomplete understanding of SSc heterogeneity. To clarify this, we have used genomic approaches to identify distinct patient subsets based on gene expression patterns in SSc skin and other end-target organs. Here, we review what is known about the gene expression-based subsets in SSc, currently defined as the inflammatory, fibroproliferative, limited, and normal-like subsets. The inflammatory subset of patients is characterized by infiltrating immune cells that include T cells, macrophages, and possibly dendritic cells, although little is known about the mediators these cells secrete and the pathways that govern cell activation. Prior studies have suggested a role for pathogens as a trigger of immune responses in SSc, and recent data have identified viral and mycobiome components as potential environmental triggers. We present a model based on analyses of gene expression data and a review of the literature, which suggests that the gene expression subsets observed in patients possibly represent distinct, interconnected molecular states of disease, to which an innate immune response is central that results in the generation of clinical disease.

Novel serum biomarkers in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) remains a difficult-to-treat condition with high mortality. Biomarkers are utilized to aid with diagnosis, prognostication and response to treatment. A clinically useful and PAH-specific single biomarker that is easy to measure remains elusive. This is in part due to the heterogeneity of PAH and its complex etiology. Brain natriuretic peptide and its N-terminal fragment are currently the most widely used serum markers; however, several novel serum biomarkers have been investigated recently. Taken individually, the evidence for each of these seems provisionally promising though currently weak overall. It is likely that a multibiomarker panel will be recommended in the future, with the optimal combination yet to be determined.

Enhanced chemokine-receptor expression, function, and signaling in healthy African American and scleroderma-patient monocytes are regulated by caveolin-1

Background

A major health disparity suffered by African Americans (AA) is a predisposition toward fibrotic diseases of the skin, lung, and other organs. We previously showed that healthy AA and scleroderma (systemic sclerosis (SSc)) patient monocytes share biochemical and functional differences from control Caucasian (C) monocytes that may predispose AA to SSc. The central difference is a decrease in caveolin-1. Low caveolin-1 levels promote monocyte migration, their differentiation into fibrocytes, and fibrocyte recruitment into fibrotic tissues. Here we have greatly expanded our studies on the mechanism of action in fibrosis of caveolin-1 in AA and SSc monocytes.

Results

Expression of chemokine receptors (CCR1, CCR2, CCR3) is enhanced in healthy AA monocytes compared to healthy C monocytes and further increased in SSc monocytes. A parallel increase in function occurs assessed by migration toward chemokines MCP-1 and MCP-3. Chemokine-receptor expression and function are inhibited by the caveolin-1 scaffolding domain peptide (CSD) via its action as a surrogate for caveolin-1. Cells bearing chemokine receptors accumulate to high levels in fibrotic lung and skin tissue from SSc patients and from mice treated with bleomycin. This accumulation is almost completely blocked in mice treated with CSD. In signaling studies, Src activation is enhanced in AA monocytes compared to C monocytes and further increased in SSc monocytes. Lyn is also highly activated in SSc monocytes. Src and Lyn activation are inhibited by CSD. Src and Lyn’s roles in monocyte migration were demonstrated using specific inhibitors.

Conclusions

To the best of our knowledge, this is the first report that the expression and function of CCR1, CCR2, and CCR3 are upregulated in monocytes from healthy AA and from SSc patients via molecular mechanisms involving caveolin-1, Src/Lyn, and MEK/ERK. The results suggest that the migration/recruitment of monocytes and fibrocytes into fibrotic tissues, mediated at least in part by CCR1, CCR2, and CCR3, plays a major role in the progression of lung and skin fibrosis and in the predisposition of AA to fibrotic diseases. Our findings further suggest that chemokine receptors and signaling molecules, particularly caveolin-1, that control their expression/function are promising targets for treating fibrotic diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13069-015-0028-7) contains supplementary material, which is available to authorized users.

Pathogenesis of Systemic Sclerosis

Systemic scleroderma (SSc) is one of the most complex systemic autoimmune diseases. It targets the vasculature, connective tissue-producing cells (namely fibroblasts/myofibroblasts), and components of the innate and adaptive immune systems. Clinical and pathologic manifestations of SSc are the result of: (1) innate/adaptive immune system abnormalities leading to production of autoantibodies and cell-mediated autoimmunity, (2) microvascular endothelial cell/small vessel fibroproliferative vasculopathy, and (3) fibroblast dysfunction generating excessive accumulation of collagen and other matrix components in skin and internal organs. All three of these processes interact and affect each other. The disease is heterogeneous in its clinical presentation that likely reflects different genetic or triggering factor (i.e., infection or environmental toxin) influences on the immune system, vasculature, and connective tissue cells. The roles played by other ubiquitous molecular entities (such as lysophospholipids, endocannabinoids, and their diverse receptors and vitamin D) in influencing the immune system, vasculature, and connective tissue cells are just beginning to be realized and studied and may provide insights into new therapeutic approaches to treat SSc.

Role of anti-inflammatory cytokines IL-4 and IL-13 in systemic sclerosis

OBJECTIVE

The aim of this paper is to review the anti-inflammatory cytokines IL-4 and IL-13 and their receptor signals; we discuss new insight into their possible roles in systemic sclerosis (SSc) and their overlapping function in SSc.

INTRODUCTION

SSc is a connective tissue disease characterized by fibrosis. The exact etiology of SSc is unknown, and no therapy has been proved effective in modifying its course. Recently the roles of IL-4 and IL-13 in the development of SSc have been extensively considered. The possible roles of IL-4 and IL-13, especially their overlapping function, in SSc are not well documented.

METHODS

A literature survey was performed using a PubMed database search to gather complete information regarding IL-4 and IL-13 and their role in inflammation.

RESULTS AND CONCLUSIONS

The participation of complex pathways of IL-4 and IL-13 in the process of inflammation and fibrosis action in SSc is still not very clear, and some pathogenesis of regulation found in vitro needs to be further proved. There is still more work which could be done to achieve useful developments with therapeutic benefit in SSc.

Interleukin 13- and interleukin 17A-induced pulmonary hypertension phenotype due to inhalation of antigen and fine particles from air pollution

Pulmonary hypertension has a marked detrimental effect on quality of life and life expectancy. In a mouse model of antigen-induced pulmonary arterial remodeling, we have recently shown that coexposure to urban ambient particulate matter (PM) significantly increased the thickening of the pulmonary arteries and also resulted in significantly increased right ventricular systolic pressures. Here we interrogate the mechanism and show that combined neutralization of interleukin 13 (IL-13) and IL-17A significantly ameliorated the increase in right ventricular systolic pressure, the circumferential muscularization of pulmonary arteries, and the molecular change in the right ventricle. Surprisingly, our data revealed a protective role of IL-17A for the antigen- and PM-induced severe thickening of pulmonary arteries. This protection was due to the inhibition of the effects of IL-13, which drove this response, and the expression of metalloelastase and resistin-like molecule α. However, the latter was redundant for the arterial thickening response. Anti-IL-13 exacerbated airway neutrophilia, which was due to a resulting excess effect of IL-17A, confirming concurrent cross inhibition of IL-13- and IL-17A-dependent responses in the lungs of animals exposed to antigen and PM. Our experiments also identified IL-13/IL-17A-independent molecular reprogramming in the lungs induced by exposure to antigen and PM, which indicates a risk for arterial remodeling and protection from arterial constriction. Our study points to IL-13- and IL-17A-coinduced inflammation as a new template for biomarkers and therapeutic targeting for the management of immune response-induced pulmonary hypertension.

Inflammation and immunity in the pathogenesis of pulmonary arterial hypertension

This review summarizes an expanding body of knowledge indicating that failure to resolve inflammation and altered immune processes underlie the development of pulmonary arterial hypertension. The chemokines and cytokines implicated in pulmonary arterial hypertension that could form a biomarker platform are discussed. Pre-clinical studies that provide the basis for dysregulated immunity in animal models of the disease are reviewed. In addition, we present therapies that target inflammatory/immune mechanisms that are currently enrolling patients, and discuss others in development. We show how genetic and metabolic abnormalities are inextricably linked to dysregulated immunity and adverse remodeling in the pulmonary arteries.

STAT3 signaling in pulmonary arterial hypertension

Pulmonary artery hypertension (PAH) is a proliferative disorder associated with enhanced pulmonary artery smooth muscle cell proliferation and suppressed apoptosis. The sustainability of this phenotype requires the activation of pro-survival transcription factor like the signal transducers and activators of transcription-3 (STAT3). Using multidisciplinary and translational approaches, we and others have demonstrated that STAT3 activation in both human and experimental models of PAH accounts for the modulation of the expression of several proteins already known as implicated in PAH pathogenesis, as well as for signal transduction to other transcription factors. Furthermore, recent data demonstrated that STAT3 could be therapeutically targeted in different animal models and some molecules are actually in clinical trials for cancer or PAH treatment.

Adventitial fibroblasts induce a distinct proinflammatory/profibrotic macrophage phenotype in pulmonary hypertension

Macrophage accumulation is not only a characteristic hallmark but is also a critical component of pulmonary artery remodeling associated with pulmonary hypertension (PH). However, the cellular and molecular mechanisms that drive vascular macrophage activation and their functional phenotype remain poorly defined. Using multiple levels of in vivo (bovine and rat models of hypoxia-induced PH, together with human tissue samples) and in vitro (primary mouse, rat, and bovine macrophages, human monocytes, and primary human and bovine fibroblasts) approaches, we observed that adventitial fibroblasts derived from hypertensive pulmonary arteries (bovine and human) regulate macrophage activation. These fibroblasts activate macrophages through paracrine IL-6 and STAT3, HIF1, and C/EBPβ signaling to drive expression of genes previously implicated in chronic inflammation, tissue remodeling, and PH. This distinct fibroblast-activated macrophage phenotype was independent of IL-4/IL-13-STAT6 and TLR-MyD88 signaling. We found that genetic STAT3 haplodeficiency in macrophages attenuated macrophage activation, complete STAT3 deficiency increased macrophage activation through compensatory upregulation of STAT1 signaling, and deficiency in C/EBPβ or HIF1 attenuated fibroblast-driven macrophage activation. These findings challenge the current paradigm of IL-4/IL-13-STAT6-mediated alternative macrophage activation as the sole driver of vascular remodeling in PH, and uncover a cross-talk between adventitial fibroblasts and macrophages in which paracrine IL-6-activated STAT3, HIF1α, and C/EBPβ signaling are critical for macrophage activation and polarization. Thus, targeting IL-6 signaling in macrophages by completely inhibiting C/EBPβ or HIF1α or by partially inhibiting STAT3 may hold therapeutic value for treatment of PH and other inflammatory conditions characterized by increased IL-6 and absent IL-4/IL-13 signaling.

Association of Interferon- and transforming growth factor β-regulated genes and macrophage activation with systemic sclerosis-related progressive lung fibrosis

OBJECTIVE

Systemic sclerosis (SSc)-related interstitial lung disease (ILD) is one of the leading causes of mortality. We undertook this study to analyze the gene expression of lung tissue in a prospective cohort of patients with SSc-related ILD and to compare it with that in control lungs and with 2 prospective clinical parameters in order to understand the molecular pathways implicated in progressive lung disease.

METHODS

Lung tissue was obtained by open lung biopsy in 28 consecutive patients with SSc-related ILD and in 4 controls. High-resolution computed tomography (HRCT) and pulmonary function testing (PFT) were performed at baseline and 2-3 years after treatment based on lung histologic classification. Microarray analysis was performed, and the results were correlated with changes in the HRCT score (FibMax) and PFT values. Quantitative polymerase chain reaction (qPCR) and immunohistochemistry were used to confirm differential levels of messenger RNA and protein.

RESULTS

Lung microarray data distinguished patients with SSc-related ILD from healthy controls. In the lungs of patients with SSc-related ILD who had nonspecific interstitial pneumonia (NSIP), expressed genes included macrophage markers, chemokines, collagen, and transforming growth factor β (TGFβ)- and interferon (IFN)-regulated genes. Expression of these genes correlated with progressive lung fibrosis defined by the change in FibMax. Immunohistochemistry confirmed increased markers of collagen (COL1A1), IFN (OAS1 and IFI44), and macrophages (CCL18 and CD163), and the positive correlation with the change in FibMax was confirmed by qPCR in a larger group of SSc patients with NSIP. Several genes correlated with both the change in FibMax (r > 0.4) and the change in % predicted forced vital capacity (r < -0.1), including IFN and macrophage markers, chemokines, and heat-shock proteins.

CONCLUSION

These results highlight major pathogenic pathways relevant to progressive pulmonary fibrosis in SSc-related ILD: macrophage emigration and activation, and up-regulated expression of TGFβ- and IFN-regulated genes.

What does global gene expression profiling tell us about the pathogenesis of systemic sclerosis?

PURPOSE OF REVIEW

The purpose of this study is to review recent hypothesis-driven studies that utilize global gene expression data for elucidating the molecular basis of systemic sclerosis (SSc) and its various clinical manifestations.

RECENT FINDINGS

The longitudinal skin gene expression studies indicate that the previously identified molecular subsets are stable over time and might identify inherent subgroups of SSc patients. Skin transcript follow-up studies indicate that the Wnt/β-catenin pathway plays an important role in promotion of fibrogenesis in fibroblasts and preadipocytes. Furthermore, the transcript profile of sclerodermatous graft-versus-host disease (sclGVHD) mice resembles the skin transcriptomes of a subgroup of SSc patientswith IL13/IL4-inducible skin signature wherein the profibrotic chemokine CCL2 plays a key role. The comparison of skin biopsies from SSc patients to skin lesions of patients with cutaneous lupus and dermatomyositis has provided valuable information about the interferon (IFN) signature in these autoimmune diseases. Furthermore, plasma IFN-inducible chemokines correlate with the IFN gene expression score in SSc patients, enabling researchers to examine this molecular signature in large SSc cohorts with serum or plasma collection.

SUMMARY

Global gene expression profiling in skin and peripheral blood can contribute to a better understanding of SSc pathogenesis and identify novel biomarkers and therapeutic targets.

CD4+ T cells and IFN-γ are required for the development of Pneumocystis-associated pulmonary hypertension

Pulmonary hypertension (PH) is a disease of diverse etiology. Although primary PH can develop in the absence of prior disease, PH more commonly develops in conjunction with other pulmonary pathologies. We previously reported a mouse model in which PH occurs as a sequela of Pneumocystis infection in the context of transient CD4 depletion. Here, we report that instead of the expected Th2 pathways, the Th1 cytokine IFN-γ is essential for the development of PH, as wild-type mice developed PH but IFN-γ knockout mice did not. Because gene expression analysis showed few strain differences that were not immune-function related, we focused on those responses as potential pathologic mechanisms. In addition to dependence on IFN-γ, we found that when CD4 cells were continuously depleted, but infection was limited by antibiotic treatment, PH did not occur, confirming that CD4 T cells are required for PH development. Also, although CD8 T-cells are implicated in the pathology of Pneumocystis pneumonia, they did not have a role in the onset of PH. Finally, we found differences in immune cell phenotypes that correlated with PH, including elevated CD204 expression in lung CD11c(+) cells, but their role remains unclear. Overall, we demonstrate that a transient, localized, immune response requiring IFN-γ and CD4-T cells can disrupt pulmonary vascular function and promote lingering PH.

Evidence for the involvement of type I interferon in pulmonary arterial hypertension

RATIONALE

Evidence is increasing of a link between interferon (IFN) and pulmonary arterial hypertension (PAH). Conditions with chronically elevated endogenous IFNs such as systemic sclerosis are strongly associated with PAH. Furthermore, therapeutic use of type I IFN is associated with PAH. This was recognized at the 2013 World Symposium on Pulmonary Hypertension where the urgent need for research into this was highlighted.

OBJECTIVE

To explore the role of type I IFN in PAH.

METHODS AND RESULTS

Cells were cultured using standard approaches. Cytokines were measured by ELISA. Gene and protein expression were measured using reverse transcriptase polymerase chain reaction, Western blotting, and immunohistochemistry. The role of type I IFN in PAH in vivo was determined using type I IFN receptor knockout (IFNAR1(-/-)) mice. Human lung cells responded to types I and II but not III IFN correlating with relevant receptor expression. Type I, II, and III IFN levels were elevated in serum of patients with systemic sclerosis associated PAH. Serum interferon γ inducible protein 10 (IP10; CXCL10) and endothelin 1 were raised and strongly correlated together. IP10 correlated positively with pulmonary hemodynamics and serum brain natriuretic peptide and negatively with 6-minute walk test and cardiac index. Endothelial cells grown out of the blood of PAH patients were more sensitive to the effects of type I IFN than cells from healthy donors. PAH lung demonstrated increased IFNAR1 protein levels. IFNAR1(-/-) mice were protected from the effects of hypoxia on the right heart, vascular remodeling, and raised serum endothelin 1 levels.

CONCLUSIONS

These data indicate that type I IFN, via an action of IFNAR1, mediates PAH.

The effects of Eculizumab on the pathology of malignant atrophic papulosis

Background

Degos disease is a frequently fatal and incurable occlusive vasculopathy most commonly affecting the skin, gastrointestinal tract and brain. Vascular C5b-9 deposition and a type I interferon (IFN) rich microenvironment are held to be pathogenetically important in the evolution of the vascular changes. We recently discovered the use of eculizumab as a salvage drug in the treatment of near fatal Malignant atrophic papulosis (MAP). The effects of eculizumab on the pathology of MAP are explored.

Methods

Archival skin and gastrointestinal biopsy material was procured over a 2.5-year period before and after eculizumab therapy in our index case. Routine light microscopy and immunohistochemical assessment for C3d, C4d, C5b-9, MxA and caspase 3 were examined. Direct immunofluorescent studies were also conducted on select biopsy material.

Results

The patient had received eculizumab as a emergent life saving measure and following rapid improvement he continued with biweekly infusions for 4 years. Although improved he continues to have signs and symptoms of persistent abdominal disease. Pre-Eculizumab biopsies showed an active thrombotic microangiopathy associated with a high type I interferon signature and extensive vascular deposits of C5b-9 in skin and gastrointestinal biopsies. Endothelial cell apoptosis as revealed by Caspase 3 expression was noted. Inflammation comprising lymphocytes and macrophages along with mesenchymal mucin was observed as well. Post-eculizumab biopsies did not show active luminal thrombosis but only chronic sequelae of prior episodes of vascular injury. There was no discernible caspase 3 expression. After 12 months of therapy, C5b-9 was no longer detectable in tissue. The high type I IFN signature and inflammation along with mucin deposition was not altered by the drug. In addition, there was little effect of the drug on the occlusive fibrointimal arteriopathy which appears to be one characterized by extensive myofibroblastic expansion of the intima potentially as revealed by staining for smooth muscle actin without immunoreactivity for desmin and myogenin.

Conclusions

Complement activation and enhanced endothelial cell apoptosis play an important role in the thrombotic complications of MAP. However, the larger vessel proliferative intimal changes appear to be independent of complement activation and may be on the basis of other upstream mechanisms. Monitoring C5b-9 deposition in tissue is likely not of great value in assessing treatment response to eculizumab given the persistence of C5b-9 in tissue for several months despite clinically effective C5 blocking therapy. A more integrated approach addressing upstream and downstream pathways in addition to those attributable to complement activation are critical for the successful treatment of MAP. Eculizumab may be used as salvage therapy in critically ill patients with thrombotic microangiopathy.

Thymic stromal lymphopoietin is up-regulated in the skin of patients with systemic sclerosis and induces profibrotic genes and intracellular signaling that overlap with those induced by interleukin-13 and transforming growth factor β

OBJECTIVE

To explore the expression of thymic stromal lymphopoietin (TSLP) in patients with diffuse cutaneous systemic sclerosis (dcSSc) and compare its effects in vivo and in vitro with those of interleukin-13 (IL-13) and transforming growth factor β (TGFβ).

METHODS

Skin biopsy specimens from patients with dcSSc (n = 14) and healthy controls (n = 13) were analyzed by immunohistochemistry and immunofluorescence for TSLP, TSLP receptor, CD4, CD8, CD31, and CD163 markers. Wild-type, IL-4Rα1-, and TSLP-deficient mice were treated with TGFβ, IL-13, poly(I-C), or TSLP by osmotic pump. Human fibroblasts and peripheral blood mononuclear cells (PBMCs) were stimulated with TGFβ, IL-13, poly(I-C), or TSLP. Microarray analysis and quantitative polymerase chain reaction were performed to determine gene expression, and protein levels of phospho-Smad2 and macrophage marker CD163 were tested.

RESULTS

TSLP was highly expressed in the skin of dcSSc patients, more strongly in perivascular areas and in immune cells, and was produced mainly by CD163+ cells. The skin of TSLP-treated mice showed up-regulated clusters of gene expression that overlapped strongly with those in IL-13- and TGFβ-treated mice. TSLP up-regulated specific genes, including CXCL9, proteasome, and interferon (IFN)-regulated genes. TSLP treatment in IL-4Rα1-deficient mice promoted similar cutaneous inflammation as in wild-type mice, though TSLP-induced arginase 1, CCL2, and matrix metalloproteinase 12 messenger RNA levels were blocked. In PBMCs, TSLP up-regulated tumor necrosis factor α, Mx-1, IFNγ, CXCL9, and mannose receptor 1 gene expression. TSLP-deficient mice treated with TGFβ showed less fibrosis and blocked expression of plasminogen activator inhibitor 1 and osteopontin 1. Poly(I-C)-treated mice showed high levels of cutaneous TSLP.

CONCLUSION

TSLP is highly expressed in the skin of dcSSc patients and interacts in a complex manner with 2 other profibrotic cytokines, TGFβ and IL-13, strongly suggesting that it might promote SSc fibrosis directly or indirectly by synergistically stimulating profibrotic genes, or production of these cytokines.

Increased expression of endoplasmic reticulum stress and unfolded protein response genes in peripheral blood mononuclear cells from patients with limited cutaneous systemic sclerosis and pulmonary arterial hypertension

OBJECTIVE

Pulmonary arterial hypertension (PAH), a common complication of limited cutaneous systemic sclerosis (lcSSc), is associated with alterations of markers of inflammation and vascular damage in peripheral blood mononuclear cells (PBMCs). Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) have been implicated in autoimmune and inflammatory diseases. The goal of this study was to assess whether markers of ER stress and the UPR are present in PBMCs from lcSSc patients with PAH.

METHODS

PBMCs were purified from 36 healthy controls, 32 lcSSc patients with PAH, and 34 lcSSc patients without PAH. Gene expression in healthy control PBMCs stimulated with thapsigargin was analyzed by DNA microarray. Genes were validated by quantitative real-time reverse transcription-polymerase chain reaction in PBMCs from healthy controls and lcSSc patients.

RESULTS

Several ER stress/UPR genes, including BiP, activating transcription factor 4 (ATF-4), ATF-6, and a spliced form of X-box binding protein 1, were up-regulated in PBMCs from lcSSc patients, with the highest levels in patients with PAH. Thapsigargin up-regulated heat-shock proteins (HSPs) and interferon (IFN)-regulated genes in PBMCs from healthy controls. Selected HSP genes (particularly DnaJB1) and IFN-related genes were also found at significantly elevated levels in PBMCs from lcSSc patients, while IFN regulatory factor 4 expression was significantly decreased. There was a positive correlation between DnaJB1 and severity of PAH (measured by pulmonary artery pressure) (r = 0.56, P < 0.05) and between ER stress markers and interleukin-6 levels (r = 0.53, P < 0.0001) in PBMCs from lcSSc patients.

CONCLUSION

This study demonstrates an association between select ER stress/UPR markers and lcSSc with PAH, suggesting that ER stress and the UPR may contribute to the altered function of circulating immune cells in lcSSc.

Scleroderma - new aspects in pathogenesis and treatment

Systemic sclerosis (SSc) is a multisystem disease with a variable clinical course and a poor prognosis corresponding to extent of microangiopathy and skin and internal organ fibrosis. Microvascular damage provokes immune cells to produce autoantibodies, pro-inflammatory and pro-fibrotic cytokines and chemokines. The hallmark of SSc is excessive collagen production by activated fibroblasts and myofibroblasts, and its accumulation in skin and internal organs. Better understanding of SSc pathogenesis resulted in the development of drugs, such as prostanoids, endothelin-1 and phosphodiesterase inhibitors, for treatment of pulmonary arterial hypertension and digital ulcers. The use of biological therapies and anti-fibrotic agents is under investigation. Stem cell transplantation seems to be promising in restarting the immune system to diminish fibrosis and restore microvasculature. Future research will be directed at genetic factors, diagnostic and prognostic markers for fibrosis and microangiopathy, and development of drugs directed to pathogenic key cells and mediators.

The immune pathogenesis of scleroderma: context is everything

The fundamental mechanisms that drive the pathogenesis of systemic sclerosis (SSc) remain elusive, despite over 50 years of investigation. Here, we review recent progress in the understanding of the immunopathogenesis of SSc. In particular, we consider interleukin-13 (IL13), and its upstream and downstream pathways, as an example of an immune system-derived mediator involved in fibrotic and vascular pathology. Emerging results linking pattern-recognition receptors and interferon pathways to SSc are also stressed. We discuss genetic data linking the immune system to SSc risk and efforts to apply animal models to subsets of patients recently resolved by gene expression profiling. These developments will help build a context for better understanding of previous observations and design of the next generation of studies that may eventually lead to effective treatment.

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.