Characterizing Lung Particulates Using Quantitative Microscopy in Coal Miners With Severe Pneumoconiosis

CONTEXT.—

Current approaches for characterizing retained lung dust using pathologists' qualitative assessment or scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) have limitations.

OBJECTIVE.—

To explore polarized light microscopy coupled with image-processing software, termed quantitative microscopy-particulate matter (QM-PM), as a tool to characterize in situ dust in lung tissue of US coal miners with progressive massive fibrosis.

DESIGN.—

We developed a standardized protocol using microscopy images to characterize the in situ burden of birefringent crystalline silica/silicate particles (mineral density) and carbonaceous particles (pigment fraction). Mineral density and pigment fraction were compared with pathologists' qualitative assessments and SEM/EDS analyses. Particle features were compared between historical (born before 1930) and contemporary coal miners, who likely had different exposures following changes in mining technology.

RESULTS.—

Lung tissue samples from 85 coal miners (62 historical and 23 contemporary) and 10 healthy controls were analyzed using QM-PM. Mineral density and pigment fraction measurements with QM-PM were comparable to consensus pathologists' scoring and SEM/EDS analyses. Contemporary miners had greater mineral density than historical miners (186 456 versus 63 727/mm3; P = .02) and controls (4542/mm3), consistent with higher amounts of silica/silicate dust. Contemporary and historical miners had similar particle sizes (median area, 1.00 versus 1.14 μm2; P = .46) and birefringence under polarized light (median grayscale brightness: 80.9 versus 87.6; P = .29).

CONCLUSIONS.—

QM-PM reliably characterizes in situ silica/silicate and carbonaceous particles in a reproducible, automated, accessible, and time/cost/labor-efficient manner, and shows promise as a tool for understanding occupational lung pathology and targeting exposure controls.

Clonal Somatic Mutations in Chronic Lung Diseases Are Associated with Reduced Lung Function

Rationale: Constantly exposed to the external environment and mutagens such as tobacco smoke, human lungs have one of the highest somatic mutation rates among all human organs. However, the relationship of these mutations to lung disease and function is not known. Objectives: To identify the prevalence and significance of clonal somatic mutations in chronic lung diseases. Methods: We analyzed the clonal somatic mutations from 1,251 samples of normal and diseased noncancerous lung tissue RNA sequencing with paired whole-genome sequencing from the Lung Tissue Research Consortium. We examined the associations of somatic mutations with lung function, disease status, and computationally deconvoluted cell types in two of the most common diseases represented in our dataset, chronic obstructive pulmonary disease (COPD; 29%) and idiopathic pulmonary fibrosis (IPF; 13%). Measurements and Main Results: Clonal somatic mutational burden was associated with reduced lung function in both COPD and IPF. We identified an increased prevalence of clonal somatic mutations in individuals with IPF compared with normal control subjects and individuals with COPD independent of age and smoking status. IPF clonal somatic mutations were enriched in disease-related and airway epithelial-expressed genes such as MUC5B in IPF. Patients who were MUC5B risk variant carriers had increased odds of developing somatic mutations of MUC5B that were explained by increased expression of MUC5B. Conclusions: Our identification of an increased prevalence of clonal somatic mutation in diseased lung that correlates with airway epithelial gene expression and disease severity highlights for the first time the role of somatic mutational processes in lung disease genetics.

Spatially distinct molecular patterns of gene expression in idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a heterogeneous disease that is pathologically characterized by areas of normal-appearing lung parenchyma, active fibrosis (transition zones including fibroblastic foci) and dense fibrosis. Defining transcriptional differences between these pathologically heterogeneous regions of the IPF lung is critical to understanding the distribution and extent of fibrotic lung disease and identifying potential therapeutic targets. Application of a spatial transcriptomics platform would provide more detailed spatial resolution of transcriptional signals compared to previous single cell or bulk RNA-Seq studies.

METHODS

We performed spatial transcriptomics using GeoMx Nanostring Digital Spatial Profiling on formalin-fixed paraffin-embedded (FFPE) tissue from 32 IPF and 12 control subjects and identified 231 regions of interest (ROIs). We compared normal-appearing lung parenchyma and airways between IPF and controls with histologically normal lung tissue, as well as histologically distinct regions within IPF (normal-appearing lung parenchyma, transition zones containing fibroblastic foci, areas of dense fibrosis, and honeycomb epithelium metaplasia).

RESULTS

We identified 254 differentially expressed genes (DEGs) between IPF and controls in histologically normal-appearing regions of lung parenchyma; pathway analysis identified disease processes such as EIF2 signaling (important for cap-dependent mRNA translation), epithelial adherens junction signaling, HIF1α signaling, and integrin signaling. Within IPF, we identified 173 DEGs between transition and normal-appearing lung parenchyma and 198 DEGs between dense fibrosis and normal lung parenchyma; pathways dysregulated in both transition and dense fibrotic areas include EIF2 signaling pathway activation (upstream of endoplasmic reticulum (ER) stress proteins ATF4 and CHOP) and wound healing signaling pathway deactivation. Through cell deconvolution of transcriptome data and immunofluorescence staining, we confirmed loss of alveolar parenchymal signals (AGER, SFTPB, SFTPC), gain of secretory cell markers (SCGB3A2, MUC5B) as well as dysregulation of the upstream regulator ATF4, in histologically normal-appearing tissue in IPF.

CONCLUSIONS

Our findings demonstrate that histologically normal-appearing regions from the IPF lung are transcriptionally distinct when compared to similar lung tissue from controls with histologically normal lung tissue, and that transition zones and areas of dense fibrosis within the IPF lung demonstrate activation of ER stress and deactivation of wound healing pathways.

Immunological and metabolic characterization of environmental Mycobacterium chimaera infection in a murine model

Mycobacterium chimaera causes pulmonary disease, but little is known of gradations in isolate virulence. Previously, 17 M. chimaera isolates were screened for survival in THP1 macrophages. "M. chimaera 1" was categorized as "more virulent" because it showed the greatest survival in macrophages, whereas "M. chimaera 2" was categorized as "less virulent" with reduced survival. Herein, we infected C3HeB/FeJ mice to compare the in vivo immune responses to M. chimaera 1 and 2. Unlike macrophages, significantly lower M. chimaera 1 counts were recovered from mouse lung tissue and BAL cells with less lung histopathologic changes compared to M. chimaera 2. Compared to M. chimaera 2, significantly more IL-1β, IL-6, and TNFα was produced early after M. chimaera 1 infection. LC-MS metabolomics analyses of BAL fluid revealed divergence in sphingolipid, phospholipid metabolism between M. chimaera 1 versus M. chimaera 2 mice. From pan-GWAS analyses, virulence and organizing DNA/molecular structure genes were associated with more virulent M. chimaera isolates. Vigorous lung-specific immune responses to M. chimaera 1 may influence effective bacterial control, but for a different isolate M. chimaera 2, subvert immune control. Continued studies of the gradations in virulence among the same NTM species will advance our understanding of NTM pathogenesis.

Pathologic Findings in Severe Coal Workers' Pneumoconiosis in Contemporary US Coal Miners

CONTEXT.—

The pathology of coal workers' pneumoconiosis (CWP) and its most severe form-progressive massive fibrosis (PMF)-in US coal miners has changed in recent years. Severe disease is occurring in younger miners and has been linked to an increase in silica dust exposure.

OBJECTIVE.—

To update the description of the pathologic features of CWP in contemporary miners compared to historical miners.

DESIGN.—

This study is a retrospective expert classification of lung tissue from 85 historical and contemporary coal miners with PMF. Significant pathologic features were scored by using a standardized instrument with consensus achieved for major findings, including newly defined categories of PMF as coal-type, mixed-type, and silica-type.

RESULTS.—

Pathologic features associated with silica dust exposure, including silica-type PMF, mineral dust alveolar proteinosis (MDAP), and immature (early stage) silicotic nodules were increased in contemporary miners. Detailed descriptions of the pathology of contemporary CWP with illustrative figures are provided.

CONCLUSIONS.—

Silica-related pathologies are more common in contemporary miners. Severe forms of CWP can be detected by subtyping PMF lesions (if present) or by identification of mature and immature silicotic nodules, coal mine dust-related alveolar proteinosis, and severe inflammation in coal miners' lungs. Silica-type PMF cases showed significantly higher levels of MDAP than either mixed- or coal-type PMF (P < .001). High profusion of birefringent silica/silicate particles was observed more frequently in cases with immature (early stage) silicotic nodules (P = .04). Severe inflammation was also significantly increased in contemporary miners (P = .03). Our findings underscore the urgent need to revise current exposure limits and monitoring of respirable crystalline silica in US coal mines.

Historical shift in pathological type of progressive massive fibrosis among coal miners in the USA

BACKGROUND

Pneumoconiosis among coal miners in the USA has been resurgent over the past two decades, despite modern dust controls and regulatory standards. Previously published studies have suggested that respirable crystalline silica (RCS) is a contributor to this disease resurgence. However, evidence has been primarily indirect, in the form of radiographic features.

METHODS

We obtained lung tissue specimens and data from the National Coal Workers' Autopsy Study. We evaluated specimens for the presence of progressive massive fibrosis (PMF) and used histopathological classifications to type these specimens into coal-type, mixed-type and silica-type PMF. Rates of each were compared by birth cohort. Logistic regression was used to assess demographic and mining characteristics associated with silica-type PMF.

RESULTS

Of 322 cases found to have PMF, study pathologists characterised 138 (43%) as coal-type, 129 (40%) as mixed-type and 55 (17%) as silica-type PMF. Among earlier birth cohorts, coal-type and mixed-type PMF were more common than silica-type PMF, but their rates declined in later birth cohorts. In contrast, the rate of silica-type PMF did not decline in cases from more recent birth cohorts. More recent year of birth was significantly associated with silica-type PMF.

CONCLUSIONS

Our findings demonstrate a shift in PMF types among US coal miners, from a predominance of coal- and mixed-type PMF to a more commonly encountered silica-type PMF. These results are further evidence of the prominent role of RCS in the pathogenesis of pneumoconiosis among contemporary US coal miners.

Lymphangioleiomyomatosis and Other Cystic Lung Diseases

Cysts and cavities in the lung are commonly encountered on chest imaging. It is necessary to distinguish thin-walled lung cysts (≤2 mm) from cavities and characterize their distribution as focal or multifocal versus diffuse. Focal cavitary lesions are often caused by inflammatory, infectious, or neoplastic processes in contrast to diffuse cystic lung diseases. An algorithmic approach to diffuse cystic lung disease can help narrow the differential diagnosis, and additional testing such as skin biopsy, serum biomarkers, and genetic testing can be confirmatory. An accurate diagnosis is essential for the management and disease surveillance of extrapulmonary complications.

Pathology and Mineralogy of the Pneumoconioses

Pneumoconioses represent the spectrum of lung diseases caused by inhalation of respirable particulate matter small enough (typically <5-µm diameter) to reach the terminal airways and alveoli. Pneumoconioses primarily occur in occupational settings where workers perform demanding and skilled manual labor including mining, construction, stone fabrication, farming, plumbing, electronics manufacturing, shipyards, and more. Most pneumoconioses develop after decades of exposure, though shorter latencies can occur from more intense particulate matter exposures. In this review, we summarize the industrial exposures, pathologic findings, and mineralogic features of various well-characterized pneumoconioses including silicosis, silicatosis, mixed-dust pneumoconiosis, coal workers' pneumoconiosis, asbestosis, chronic beryllium disease, aluminosis, hard metal pneumoconiosis, and some less severe pneumoconioses. We also review a general framework for the diagnostic work-up of pneumoconioses for pulmonologists including obtaining a detailed occupational and environmental exposure history. Many pneumoconioses are irreversible and develop due to excessive cumulative respirable dust inhalation. Accurate diagnosis permits interventions to minimize ongoing fibrogenic dust exposure. A consistent occupational exposure history coupled with typical chest imaging findings is usually sufficient to make a clinical diagnosis without the need for tissue sampling. Lung biopsy may be required when exposure history, imaging, and testing are inconsistent, there are unusual or new exposures, or there is a need to obtain tissue for another indication such as suspected malignancy. Close collaboration and information-sharing with the pathologist prior to biopsy is of great importance for diagnosis, as many occupational lung diseases are missed due to insufficient communication. The pathologist has a broad range of analytic techniques including bright-field microscopy, polarized light microscopy, and special histologic stains that may confirm the diagnosis. Advanced techniques for particle characterization such as scanning electron microscopy/energy dispersive spectroscopy may be available in some centers.

Dichotomous role of integrin-β5 in lung endothelial cells

Pulmonary arterial hypertension (PAH) is a progressive, devastating disease, and its main histological manifestation is an occlusive pulmonary arteriopathy. One important functional component of PAH is aberrant endothelial cell (EC) function including apoptosis-resistance, unchecked proliferation, and impaired migration. The mechanisms leading to and maintaining physiologic and aberrant EC function are not fully understood. Here, we tested the hypothesis that in PAH, ECs have increased expression of the transmembrane protein integrin-β5, which contributes to migration and survival under physiologic and pathological conditions, but also to endothelial-to-mesenchymal transition (EnMT). We found that elevated integrin-β5 expression in pulmonary artery lesions and lung tissue from PAH patients and rats with PH induced by chronic hypoxia and injection of CD117+ rat lung EC clones. These EC clones exhibited elevated expression of integrin-β5 and its heterodimerization partner integrin-αν and showed accelerated barrier formation. Inhibition of integrin-ανβ5 in vitro partially blocked transforming growth factor (TGF)-β1-induced EnMT gene expression in rat lung control ECs and less in rat lung EC clones and human lung microvascular ECs. Inhibition of integrin-ανβ5 promoted endothelial dysfunction as shown by reduced migration in a scratch assay and increased apoptosis in synergism with TGF-β1. In vivo, blocking of integrin-ανβ5 exaggerated PH induced by chronic hypoxia and CD117+ EC clones in rats. In summary, we found a role for integrin-ανβ5 in lung endothelial survival and migration, but also a partial contribution to TGF-β1-induced EnMT gene expression. Our results suggest that integrin-ανβ5 is required for physiologic function of ECs and lung vascular homeostasis.

Characterization of Immune Cells From the Lungs of Patients With Chronic Non-Tuberculous Mycobacteria or Pseudomonas aeruginosa Infection

Little is known of the lung cellular immunophenotypes in patients with non-tuberculous mycobacterial lung disease (NTM-LD). Flow-cytometric analyses for the major myeloid and lymphoid cell subsets were performed in less- and more-diseased areas of surgically resected lungs from six patients with NTM-LD and two with Pseudomonas aeruginosa lung disease (PsA-LD). Lymphocytes, comprised mainly of NK cells, CD4⁺ and CD8⁺ T cells, and B cells, accounted for ~60% of all leukocytes, with greater prevalence of T and B cells in more-diseased areas. In contrast, fewer neutrophils were found with decreased number in more-diseased areas. Compared to NTM-LD, lung tissues from patients with PsA-LD demonstrated relatively lower numbers of T and B lymphocytes but similar numbers of NK cells. While this study demonstrated a large influx of lymphocytes into the lungs of patients with chronic NTM-LD, further analyses of their phenotypes are necessary to determine the significance of these findings.

Histopathologic Analysis of Surgically Resected Lungs of Patients with Non-tuberculous Mycobacterial Lung Disease: a Retrospective and Hypothesis-generating Study

Non-tuberculous mycobacterial lung disease (NTM-LD) is most commonly due to species within the Mycobacterium avium complex (MAC) and Mycobacterium abscessus complex (MAbC). Surgical lung resection, typically a lobectomy or segmentectomy, is occasionally undertaken for individuals with recalcitrant but localized NTM-LD. Since the growth characteristics of MAC (slow growers) and MAbC (rapid growers) as well as their drug susceptibility patterns are significantly different, the objective of this study is to characterize and compare the histopathologic features of the resected lungs due to these two major NTM groups. From 1996 to 2017, 356 patients with NTM-LD due to MAC (n=270), MAbC (n=54), or both (n=32) underwent a total of 404 lobar resections (with the lingula counted as a separate lobe) at the University of Colorado Hospital. We analyzed by microscopy the existing surgical lung tissue sections for bronchiolitis, bronchiolectasis, bronchiectasis, non-necrotizing granuloma (airway, parenchymal, and total), necrotizing granuloma (airway, parenchymal, and total), peri-airway fibrosis, fibrous pleuritis, and lymphoid follicles. There were no significant differences in the presence or absence of most of the histopathologic features of surgically removed lungs due to MAC, MAbC, or both MAC + MAbC. However, there were significantly more necrotizing granulomas (airway, parenchymal, and total) and fibrous pleuritis in MAC compared to MAbC lung diseases. Since necrotizing granulomas may be a sign of inadequate control of the infection, we posit that their presence may be an indication of increased chronicity, increased virulence of MAC compared to MAbC, and/or impaired host immunity against the NTM. Futures studies to determine the root cause of such differences in histopathologic findings in MAC versus MAbC lung disease may spawn new leads on differential pathogenic mechanisms with different NTM, with the goal of aiming for more targeted therapy against both the NTM and the lung damage induced by them.

Histopathological Correlation of Acute on Chronic Eosinophilic Pneumonitis Caused by Vaporized Cannabis Oil Inhalation

Whether eosinophilic pneumonitis represents a true manifestation of e-cigarette, or vaping, product use-associated lung injury remains uncertain, and this ambiguity stems from a lack of histopathological data. We present a previously healthy young woman whose asthma-like symptoms and histopathologic finding of eosinophilic pneumonitis were caused by inhalation of vaporized cannabis hash oil concentrates. This report provides compelling evidence that eosinophilic pneumonitis can result from cannabis hash oil inhalation.

Chronic Hypersensitivity Pneumonitis, an Interstitial Lung Disease with Distinct Molecular Signatures

Rationale: Chronic hypersensitivity pneumonitis (CHP) is caused by an immune response to antigen inhalation and is characterized by variable histopathological and clinical features. A subset of subjects with CHP have usual interstitial pneumonia and appear to be clinically similar to subjects with idiopathic pulmonary fibrosis (IPF).Objectives: To determine the common and unique molecular features of CHP and IPF.Methods: Transcriptome analysis of lung samples from CHP (n = 82), IPF (n = 103), and unaffected controls (n = 103) was conducted. Differential gene expression was determined adjusting for sex, race, age, and smoking history and using false discovery rate to control for multiple comparisons.Measurements and Main Results: When compared with controls, we identified 413 upregulated and 317 downregulated genes in CHP and 861 upregulated and 322 downregulated genes in IPF. Concordantly upregulated or downregulated genes in CHP and IPF were related to collagen catabolic processes and epithelial development, whereas genes specific to CHP (differentially expressed in CHP when compared with control and not differentially expressed in IPF) were related to chemokine-mediated signaling and immune responsiveness. Using weighted gene coexpression network analysis, we found that among subjects with CHP, genes involved in adaptive immunity or epithelial cell development were associated with improved or reduced lung function, respectively, and that MUC5B expression was associated with epithelial cell development. MUC5B expression was also associated with lung fibrosis and honeycombing.Conclusions: Gene expression analysis of CHP and IPF identified signatures common to CHP and IPF, as well as genes uniquely expressed in CHP. Select modules of gene expression are characterized by distinct clinical and pathological features of CHP.

Rituximab and antimetabolite treatment of granulomatous and lymphocytic interstitial lung disease in common variable immunodeficiency

BACKGROUND

Granulomatous and lymphocytic interstitial lung disease (GLILD) is a life-threatening complication in patients with common variable immunodeficiency (CVID), but the optimal treatment is unknown.

OBJECTIVE

Our aim was to determine whether rituximab with azathioprine or mycophenolate mofetil improves the high-resolution computed tomography (HRCT) chest scans and/or pulmonary function test results in patients with CVID and GLILD.

METHODS

A retrospective chart review of clinical and laboratory data on 39 patients with CVID and GLILD who completed immunosuppressive therapy was performed. Chest HRCT scans, performed before therapy and after the conclusion of therapy, were blinded, randomized, and scored independently by 2 radiologists. Differences between pretreatment and posttreatment HRCT scan scores, pulmonary function test results, and lymphocyte subsets were analyzed. Whole exome sequencing was performed on all patients.

RESULTS

Immunosuppressive therapy improved patients' HRCT scan scores (P < .0001), forced vital capacity (P = .0017), FEV₁ (P = .037), and total lung capacity (P = .013) but not their lung carbon monoxide diffusion capacity (P = .12). Nine patients relapsed and 6 completed retreatment, with 5 of 6 of these patients (83%) having improved HRCT scan scores (P = .063). Relapse was associated with an increased number of B cells (P = .016) and activated CD4 T cells (P = .016). Four patients (10%) had pneumonia while undergoing active treatment, and 2 patients (5%) died after completion of therapy. Eight patients (21%) had a damaging mutation in a gene known to predispose (TNFRSF13B [n = 3]) or cause a CVID-like primary immunodeficiency (CTLA4 [n = 2], KMT2D [n = 2], or BIRC4 [n = 1]). Immunosuppression improved the HRCT scan scores in patients with (P = .0078) and without (P < .0001) a damaging mutation.

CONCLUSIONS

Immunosuppressive therapy improved the radiographic abnormalities and pulmonary function of patients with GLILD. A majority of patients had sustained remissions.

The hallmarks of severe pulmonary arterial hypertension: the cancer hypothesis-ten years later

Severe forms of pulmonary arterial hypertension (PAH) are most frequently the consequence of a lumen-obliterating angiopathy. One pathobiological model is that the initial pulmonary vascular endothelial cell injury and apoptosis is followed by the evolution of phenotypically altered, apoptosis-resistant, proliferating cells and an inflammatory vascular immune response. Although there may be a vasoconstrictive disease component, the increased pulmonary vascular shear stress in established PAH is caused largely by the vascular wall pathology. In this review, we revisit the "quasi-malignancy concept" of severe PAH and examine to what extent the hallmarks of PAH can be compared with the hallmarks of cancer. The cancer model of severe PAH, based on the growth of abnormal vascular and bone marrow-derived cells, may enable the emergence of novel cell-based PAH treatment strategies.

Endothelial cells are a source of Nestin expression in Pulmonary Arterial Hypertension

Uncontrolled proliferation of endothelial cells is essential to the pathogenesis of pulmonary arterial hypertension (PAH). Both proliferation and cytoskeleton reorganization are associated with upregulation of the intermediate filament protein Nestin. Recently, accumulation of Nestin-expressing cells was found in pulmonary vascular lesions of PAH patients. The goal of this study is to determine if Nestin expression contributes to endothelial proliferation in pulmonary arterial hypertension, using both lung tissues and endothelial cells. Here we found that endothelial cells from complex and plexiform lesions of PAH patients expressed Nestin. These Nestin+ cells further stained positive for the angiogenic factors CXC chemokine ligand 12 and Wnt1. Likewise, in the chronic hypoxia/SU5416 animal model of pulmonary hypertension, Nestin+ endothelial cells were found in occlusive pulmonary vascular lesions. In vitro, both growing rat and human lung endothelial cells expressed Nestin protein. When Nestin was overexpressed in endothelial cells (both rat and human), Nestin overexpression promoted proliferation and expression of CXC chemokine ligand 12. Nestin overexpression further increased angiogenic tube formation in vitro. Conclusions: We found increased Nestin expression from endothelial cells of occlusive lung vascular lesions in severe pulmonary hypertension. Elevated Nestin expression likely contributes to unchecked pulmonary vascular proliferation and angiogenesis, possibly via induction of CXC chemokine ligand 12. Additional studies are required to determine whether targeting Nestin would be beneficial to treat PAH.

Toll-like Receptor 3 Is a Therapeutic Target for Pulmonary Hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is characterized by vascular cell proliferation and endothelial cell apoptosis. TLR3 (Toll-like receptor 3) is a receptor for double-stranded RNA and has been recently implicated in vascular protection.

OBJECTIVES

To study the expression and role of TLR3 in PAH and to determine whether a TLR3 agonist reduces pulmonary hypertension in preclinical models.

METHODS

Lung tissue and endothelial cells from patients with PAH were investigated by polymerase chain reaction, immunofluorescence, and apoptosis assays. TLR3-/- and TLR3+/+ mice were exposed to chronic hypoxia and SU5416. Chronic hypoxia or chronic hypoxia/SU5416 rats were treated with the TLR3 agonist polyinosinic/polycytidylic acid (Poly[I:C]).

MEASUREMENTS AND MAIN RESULTS

TLR3 expression was reduced in PAH patient lung tissue and endothelial cells, and TLR3-/- mice exhibited more severe pulmonary hypertension following exposure to chronic hypoxia/SU5416. TLR3 knockdown promoted double-stranded RNA signaling via other intracellular RNA receptors in endothelial cells. This was associated with greater susceptibility to apoptosis, a known driver of pulmonary vascular remodeling. Poly(I:C) increased TLR3 expression via IL-10 in rat endothelial cells. In vivo, high-dose Poly(I:C) reduced pulmonary hypertension in both rat models in proof-of-principle experiments. In addition, Poly(I:C) also reduced right ventricular failure in established pulmonary hypertension.

CONCLUSIONS

Our work identifies a novel role for TLR3 in PAH based on the findings that reduced expression of TLR3 contributes to endothelial apoptosis and pulmonary vascular remodeling.

Protein Tyrosine Phosphatase-N13 Promotes Myofibroblast Resistance to Apoptosis in Idiopathic Pulmonary Fibrosis

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a progressive, fibrotic interstitial lung disease characterized by (myo)fibroblast accumulation and collagen deposition. Resistance to Fas-induced apoptosis is thought to facilitate (myo)fibroblast persistence in fibrotic lung tissues by poorly understood mechanisms.

OBJECTIVES

To test the hypothesis that PTPN13 (protein tyrosine phosphatase-N13) is expressed by IPF lung (myo)fibroblasts, promotes their resistance to Fas-induced apoptosis, and contributes to the development of pulmonary fibrosis.

METHODS

PTPN13 was localized in lung tissues from patients with IPF and control subjects by immunohistochemical staining. Inhibition of PTPN13 function in primary IPF and normal lung (myo)fibroblasts was accomplished by: 1) downregulation with TNF-α (tumor necrosis factor-α)/IFN-γ, 2) siRNA knockdown, or 3) a cell-permeable Fas/PTPN13 interaction inhibitory peptide. The role of PTPN13 in the development of pulmonary fibrosis was assessed in mice with genetic deficiency of PTP-BL, the murine ortholog of PTPN13.

MEASUREMENTS AND MAIN RESULTS

PTPN13 was constitutively expressed by (myo)fibroblasts in the fibroblastic foci of patients with IPF. Human lung (myo)fibroblasts, which are resistant to Fas-induced apoptosis, basally expressed PTPN13 in vitro. TNF-α/IFN-γ or siRNA-mediated PTPN13 downregulation and peptide-mediated inhibition of the Fas/PTPN13 interaction in human lung (myo)fibroblasts promoted Fas-induced apoptosis. Bleomycin-challenged PTP-BL-/- mice, while developing inflammatory lung injury, exhibited reduced pulmonary fibrosis compared with wild-type mice.

CONCLUSIONS

These findings suggest that PTPN13 mediates the resistance of human lung (myo)fibroblasts to Fas-induced apoptosis and promotes pulmonary fibrosis in mice. Our results suggest that strategies aimed at interfering with PTPN13 expression or function may represent a novel strategy to reduce fibrosis in IPF.

AIBP augments cholesterol efflux from alveolar macrophages to surfactant and reduces acute lung inflammation

Acute respiratory distress syndrome (ARDS) is characterized by an excessive pulmonary inflammatory response. Removal of excess cholesterol from the plasma membrane of inflammatory cells helps reduce their activation. The secreted apolipoprotein A-I binding protein (AIBP) has been shown to augment cholesterol efflux from endothelial cells to the plasma lipoprotein HDL. Here, we find that AIBP was expressed in inflammatory cells in the human lung and was secreted into the bronchoalveolar space in mice subjected to inhalation of LPS. AIBP bound surfactant protein B and increased cholesterol efflux from alveolar macrophages to calfactant, a therapeutic surfactant formulation. In vitro, AIBP in the presence of surfactant reduced LPS-induced p65, ERK1/2 and p38 phosphorylation, and IL-6 secretion by alveolar macrophages. In vivo, inhalation of AIBP significantly reduced LPS-induced airspace neutrophilia, alveolar capillary leak, and secretion of IL-6. These results suggest that, similar to HDL in plasma, surfactant serves as a cholesterol acceptor in the lung. Furthermore, lung injury increases pulmonary AIBP expression, which likely serves to promote cholesterol efflux to surfactant and reduce inflammation.

The relationship between complement C3 expression and the MUC5B genotype in pulmonary fibrosis

The common gain-of-function MUC5B promoter variant ( rs35705950 ) is the strongest risk factor for the development of idiopathic pulmonary fibrosis (IPF). While the role of complement in IPF is controversial, both MUC5B and the complement system play a role in lung host defense. The aim of this study was to evaluate the relationship between complement component 3 (C3) and MUC5B in patients with IPF and in bleomycin-induced lung injury in mice. To do this, we evaluated C3 gene expression in whole lung tissue from 300 subjects with IPF and 175 healthy controls. Expression of C3 was higher in IPF than healthy controls {1.40-fold increase [95% confidence interval (CI) 1.31-1.50]; P < 0.0001} and even greater among IPF subjects with the highest-risk IPF MUC5B promoter genotype [TT vs. GG = 1.59-fold (95% CI 1.15-2.20); P < 0.05; TT vs. GT = 1.66-fold (95% CI 1.20-2.30); P < 0.05]. Among subjects with IPF, C3 expression was significantly higher in the lung tissue without microscopic honeycombing than in the lung tissue with microscopic honeycombing [1.40-fold increase (95% CI 1.23- 1.59); P < 0.01]. In mice, while bleomycin exposure increased Muc5b protein expression, C3-deficient mice were protected from bleomycin-induced lung injury. In aggregate, our findings indicate that the MUC5B promoter variant is associated with higher C3 expression and suggest that the complement system may contribute to the pathogenesis of IPF.

Circulating endothelial cells in pulmonary hypertension

The pulmonary endothelium plays a significant role in the pathobiology of Primary Pulmonary Hypertension. A number of diseases, related by a history of vascular injury, are associated with increased numbers of circulating endothelial cells (CECs). We hypothesized that patients with pulmonary hypertension would also have an increased number of circulating endothelial cells due to the high pressures and increased shear stress present within the pulmonary vasculature. We isolated the CECs from 14 patients with pulmonary hypertension, (5 primary and 11 secondary) and compared them to the cells from 12 normal controls. There was a significant increase in the number of CECs in peripheral blood in patients with both PPH and secondary pulmonary hypertension (SPH) when compared to normal volunteers (33.1 +/- 1.9 {PPH} and 27.2 +/- 6.9 {SPH} vs. 3.5 +/- 1.3 {controls}, p < 0.001). The number of circulating endothelial cells in the patient’s peripheral blood correlated significantly with the systolic, diastolic and mean pulmonary artery pressures of the individual. Approximately 50% of the CECs from patients with pulmonary hypertension expressed CD36, a marker of microvascular origin and 25% expressed E-selectin, a marker of endothelial cell activation. Although the origin of the CECs in patients with PH requires further investigation, one possible source is the pulmonary vasculature, and in patients with plexogenic pulmonary hypertension, the plexiform lesions. CECs may provide a non-invasive mean of accessing cells important to the pathobiology of severe pulmonary hypertension.

RNA sequencing and pathway analysis identify tumor necrosis factor alpha driven small proline-rich protein dysregulation in chronic rhinosinusitis

BACKGROUND

Chronic rhinosinusitis (CRS) is a heterogeneous inflammatory disorder in which many pathways contribute to end-organ disease. Small proline-rich proteins (SPRR) are polypeptides that have recently been shown to contribute to epithelial biomechanical properties relevant in T-helper type 2 inflammation. There is evidence that genetic polymorphism in SPRR genes may predict the development of asthma in children with atopy and, correlatively, that expression of SPRRs is increased under allergic conditions, which leads to epithelial barrier dysfunction in atopic disease.

METHODS

RNAs from uncinate tissue specimens from patients with CRS and control subjects were compared by RNA sequencing by using Ingenuity Pathway Analysis (n = 4 each), and quantitative polymerase chain reaction (PCR) (n = 15). A separate cohort of archived sinus tissue was examined by immunohistochemistry (n = 19).

RESULTS

A statistically significant increase of SPRR expression in CRS sinus tissue was identified that was not a result of atopic presence. SPRR1 and SPRR2A expressions were markedly increased in patients with CRS (p < 0.01) on RNA sequencing, with confirmation by using real-time PCR. Immunohistochemistry of archived surgical samples demonstrated staining of SPRR proteins within squamous epithelium of both groups. Pathway analysis indicated tumor necrosis factor (TNF) alpha as a master regulator of the SPRR gene products.

CONCLUSION

Expression of SPRR1 and of SPRR2A is increased in mucosal samples from patients with CRS and appeared as a downstream result of TNF alpha modulation, which possibly resulted in epithelial barrier dysfunction.

p53 Signaling Pathway Polymorphisms Associated With Emphysematous Changes in Patients With COPD

BACKGROUND

The p53 signaling pathway may be important for the pathogenesis of emphysematous changes in the lungs of smokers. Polymorphism of p53 at codon 72 is known to affect apoptotic effector proteins, and the polymorphism of mouse double minute 2 homolog (MDM2) single nucleotide polymorphism (SNP)309 is known to increase MDM2 expression. The aim of this study was to assess polymorphisms of the p53 and MDM2 genes in smokers and confirm the role of SNPs in these genes in the pathogenesis of pulmonary emphysema.

METHODS

This study included 365 patients with a smoking history, and the polymorphisms of p53 and MDM2 genes were identified. The degree of pulmonary emphysema was determined by means of CT scanning. SNPs, MDM2 mRNA, and p53 protein levels were assessed in human lung tissues from smokers. Plasmids encoding p53 and MDM2 SNPs were used to transfect human lung fibroblasts (HLFs) with or without cigarette smoke extract (CSE), and the effects on cell proliferation and MDM2 promoter activity were measured.

RESULTS

The polymorphisms of the p53 and MDM2 genes were associated with emphysematous changes in the lung and were also associated with p53 protein and MDM2 mRNA expression in the lung tissue samples. Transfection with a p53 gene-coding plasmid regulated HLF proliferation, and the analysis of P2 promoter activity in MDM2 SNP309-coding HLFs showed the promoter activity was altered by CSE.

CONCLUSIONS

Our data demonstrated that p53 and MDM2 gene polymorphisms are associated with apoptotic signaling and smoking-related emphysematous changes in lungs from smokers.

K-homology splicing regulatory protein (KSRP) promotes post-transcriptional destabilization of Spry4 transcripts in non-small cell lung cancer

AU-rich element-binding proteins (ARE-BPs) offer post-transcriptional regulation of gene expression via physical interaction and recruitment of RNA decay machinery to the AU-rich elements within the 3′-UTR of the target transcripts. However, the role of ARE-BPs in lung cancer remains poorly understood. In this study, we have identified that K-homology splicing regulatory protein (KSRP), an ARE-BP, is robustly up-regulated in human lung cancer. Importantly, Kaplan-Meier survival analysis indicated that elevated KSRP expression was correlated with poor overall survival of lung cancer patients. Furthermore, cigarette smoke, a leading risk factor for lung cancer, was also identified to be an important contributor to increased KSRP expression. Remarkably, silencing of KSRP decreased cell proliferation, reversed anchorage-independent growth, and reduced migration/invasion, suggesting an oncogenic role for KSRP in lung cancer. Finally, we provide mechanistic evidence that KSRP promotes the down-regulation of Spry4 by a previously unidentified mechanism, i.e. post-transcriptional mRNA regulation.

CT scan findings of probable usual interstitial pneumonitis have a high predictive value for histologic usual interstitial pneumonitis

BACKGROUND

The current usual interstitial pneumonitis (UIP)/idiopathic pulmonary fibrosis CT scan classification system excludes probable UIP as a diagnostic category. We sought to determine the predictive effect of probable UIP on CT scan on histology and the effect of the promoter polymorphism in MUC5B (rs35705950) on histologic and CT scan UIP diagnosis.

METHODS

The cohort included 201 subjects with pulmonary fibrosis who had lung tissue samples obtained within 1 year of chest CT scan. UIP diagnosis on CT scan was categorized as inconsistent with, indeterminate, probable, or definite UIP by two to three pulmonary radiologists. Tissue slides were scored by two expert pulmonary pathologists. All subjects with available DNA (N = 200) were genotyped for rs35705950.

RESULTS

The proportion of CT scan diagnoses were as follows: inconsistent with (69 of 201, 34.3%), indeterminate (72 of 201, 35.8%), probable (34 of 201, 16.9%), and definite (26 of 201, 12.9%) UIP. Subjects with probable UIP on CT scan were more likely to have histologic probable/definite UIP than subjects with indeterminate UIP on CT scan (82.4% [28 of 34] vs 54.2% [39 of 72]; P = .01). CT scan and microscopic honeycombing were not associated with each other (P = .76). The minor (T) allele of the MUC5B polymorphism was associated with concordant CT scan and histologic UIP diagnosis (P = .03).

CONCLUSIONS

Probable UIP on CT scan is associated with a higher rate of histologic UIP than indeterminate UIP on CT scan suggesting that they are distinct groups and should not be combined into a single CT scan category as currently recommended by guidelines. CT scan and microscopic honeycombing may be dissimilar entities. The T allele at rs35705950 predicts a UIP diagnosis by both chest CT scan and histology.

Nuclear factor κB inhibition reduces lung vascular lumen obliteration in severe pulmonary hypertension in rats

NF-κB and IL-6, a NF-κB downstream mediator, play a central role in the inflammatory response of tissues. We aimed to determine the role of the classical NF-κB pathway in severe pulmonary arterial hypertension (PAH) induced by SU5416 and chronic hypoxia (SuHx) in rats. Tissue samples from patients with idiopathic PAH (iPAH) and control subjects were investigated. SuHx rats were treated from Days 1 to 3, 1 to 21, and 29 to 42 with the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC) and/or from Days 1 to 21 with anti-IL-6 antibody. Nuclear staining for NF-κB, an indicator of the activation of the classical NF-κB pathway, was detected in pulmonary arterial lesions of patients with iPAH and SuHx rats. NF-κB inhibition with PDTC prevented and reduced pulmonary arterial obliteration without reducing muscularization. However, the elevated lung levels of IL-6 were not reduced in PDTC-treated SuHx animals. PDTC treatment prevented or reduced apoptosis of pulmonary artery wall cells and pulmonary arterial obliteration. IL-6 inhibition had only a partial effect on apoptosis and obliteration. Pulmonary arterial media wall thickness was not affected by any of these treatments. Preventive and therapeutic PDTC treatment promoted immune regulation by increasing the number of perivascular CD4(+) T cells, in particular regulatory T cells (early treatment), and by reducing the number of perivascular CD8(+) T lymphocytes and CD45RA(+) B lymphocytes. Therapeutic PDTC treatment further preserved right ventricular function in SuHx animals. Inhibition of NF-κB may represent a therapeutic option for pulmonary arterial obliteration via reduced vessel wall cell apoptosis and improved regulation of the immune system.

Glutaredoxin-1 attenuates S-glutathionylation of the death receptor fas and decreases resolution of Pseudomonas aeruginosa pneumonia

RATIONALE

The death receptor Fas is critical for bacterial clearance and survival of mice after Pseudomonas aeruginosa infection.

OBJECTIVES

Fas ligand (FasL)-induced apoptosis is augmented by S-glutathionylation of Fas (Fas-SSG), which can be reversed by glutaredoxin-1 (Grx1). Therefore, the objective of this study was to investigate the interplay between Grx1 and Fas in regulating the clearance of P. aeruginosa infection.

METHODS

Lung samples from patients with bronchopneumonia were analyzed by immunofluorescence. Primary tracheal epithelial cells, mice lacking the gene for Grx1 (Glrx1(-/-)), Glrx1(-/-) mice treated with caspase inhibitor, or transgenic mice overexpressing Grx1 in the airway epithelium were analyzed after infection with P. aeruginosa.

MEASUREMENTS AND MAIN RESULTS

Patient lung samples positive for P. aeruginosa infection demonstrated increased Fas-SSG compared with normal lung samples. Compared with wild-type primary lung epithelial cells, infection of Glrx1(-/-) cells with P. aeruginosa showed enhanced caspase 8 and 3 activities and cell death in association with increases in Fas-SSG. Infection of Glrx1(-/-) mice with P. aeruginosa resulted in enhanced caspase activity and increased Fas-SSG as compared with wild-type littermates. Absence of Glrx1 significantly enhanced bacterial clearance, and decreased mortality postinfection with P. aeruginosa. Inhibition of caspases significantly decreased bacterial clearance postinfection with P. aeruginosa, in association with decreased Fas-SSG. In contrast, transgenic mice that overexpress Grx1 in lung epithelial cells had significantly higher lung bacterial loads, enhanced mortality, decreased caspase activation, and Fas-SSG in the lung after infection with P. aeruginosa, compared with wild-type control animals.

CONCLUSIONS

These results suggest that S-glutathionylation of Fas within the lung epithelium enhances epithelial apoptosis and promotes clearance of P. aeruginosa and that glutaredoxin-1 impairs bacterial clearance and increases the severity of pneumonia in association with deglutathionylation of Fas.

CXCR4 inhibition ameliorates severe obliterative pulmonary hypertension and accumulation of C-kit⁺ cells in rats

Successful curative treatment of severe pulmonary arterial hypertension with luminal obliteration will require a thorough understanding of the mechanism underlying the development and progression of pulmonary vascular lesions. But the cells that obliterate the pulmonary arterial lumen in severe pulmonary arterial hypertension are incompletely characterized. The goal of our study was to evaluate whether inhibition of CXC chemokine receptor 4 will prevent the accumulation of c-kit⁺ cells and severe pulmonary arterial hypertension. We detected c-kit⁺⁻ cells expressing endothelial (von Willebrand Factor) or smooth muscle cell/myofibroblast (α-smooth muscle actin) markers in pulmonary arterial lesions of SU5416/chronic hypoxia rats. We found increased expression of CXC chemokine ligand 12 in the lung tissue of SU5416/chronic hypoxia rats. In our prevention study, AMD3100, an inhibitor of the CXC chemokine ligand 12 receptor, CXC chemokine receptor 4, only moderately decreased pulmonary arterial obliteration and pulmonary hypertension in SU5416/chronic hypoxia animals. AMD3100 treatment reduced the number of proliferating c-kit⁺ α-smooth muscle actin⁺ cells and pulmonary arterial muscularization and did not affect c-kit⁺ von Willebrand Factor⁺ cell numbers. Both c-kit⁺ cell types expressed CXC chemokine receptor 4. In conclusion, our data demonstrate that in the SU5416/chronic hypoxia model of severe pulmonary hypertension, the CXC chemokine receptor 4-expressing c-kit⁺ α-smooth muscle actin⁺ cells contribute to pulmonary arterial muscularization. In contrast, vascular lumen obliteration by c-kit⁺ von Willebrand Factor⁺ cells is largely independent of CXC chemokine receptor 4.

IL-32 promotes angiogenesis

IL-32 is a multifaceted cytokine with a role in infections, autoimmune diseases, and cancer, and it exerts diverse functions, including aggravation of inflammation and inhibition of virus propagation. We previously identified IL-32 as a critical regulator of endothelial cell (EC) functions, and we now reveal that IL-32 also possesses angiogenic properties. The hyperproliferative ECs of human pulmonary arterial hypertension and glioblastoma multiforme exhibited a markedly increased abundance of IL-32, and, significantly, the cytokine colocalized with integrin αVβ3. Vascular endothelial growth factor (VEGF) receptor blockade, which resulted in EC hyperproliferation, increased IL-32 three-fold. Small interfering RNA-mediated silencing of IL-32 negated the 58% proliferation of ECs that occurred within 24 h in scrambled-transfected controls. Reduction of IL-32 neither affected apoptosis (insignificant changes in Bak-1, Bcl-2, Bcl-xL, lactate dehydrogenase, annexin V, and propidium iodide) nor VEGF or TGF-β levels, but siIL-32-transfected adult and neonatal ECs produced up to 61% less NO, IL-8, and matrix metalloproteinase-9, and up to 3-fold more activin A and endostatin. In coculture-based angiogenesis assays, IL-32γ dose-dependently increased tube formation up to 3-fold; an αVβ3 inhibitor prevented this activity and reduced IL-32γ-induced IL-8 by 85%. In matrigel plugs loaded with IL-32γ, VEGF, or vehicle and injected into live mice, we observed the anticipated VEGF-induced increase in neocapillarization (8-fold versus vehicle), but unexpectedly, IL-32γ was equally angiogenic. A second signal such as IFN-γ was required to render cells responsive to exogenous IL-32γ; importantly, this was confirmed using a completely synthetic preparation of IL-32γ. In summary, we add angiogenic properties that are mediated by integrin αVβ3 but VEGF-independent to the portfolio of IL-32, implicating a role for this versatile cytokine in pulmonary arterial hypertension and neoplastic diseases.

Fibrosing interstitial pneumonia predicts survival in patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD)

BACKGROUND

Rheumatoid arthritis (RA) is a systemic autoimmune disorder with a variety of extra-articular manifestations. The lung is a common target and diffuse parenchymal lung disease can appear as any of the patterns found with idiopathic interstitial pneumonia. Controversy exists as to the prognostic significance of these patterns among patients with RA-ILD.

METHODS

We retrospectively identified 48 patients with a diagnosis of RA-ILD confirmed by surgical lung biopsy. The pathology was reviewed by four expert pulmonary pathologists. We examined survival after stratifying on the presence or absence of fibrotic ILD, and contrasted it with a matched idiopathic pulmonary fibrosis (IPF) population. The Cox proportional hazards model was used to identify independent predictors of survival.

RESULTS

The majority of subjects were male smokers with physiologic restriction. A usual interstitial pneumonia (UIP)-pattern was identified in 31% of subjects. Median survival time for the entire cohort was 1360 days. Subjects with fibrotic ILD had worse survival than subjects with non-fibrotic ILD (log rank p = 0.02). There was no difference in survival between UIP-pattern RA-ILD subjects and IPF controls (log rank p = 0.94). Multivariable analysis revealed that age (hazard ratio [HR] = 1.04, p = 0.01) and fibrosis (HR = 2.1, p = 0.02) were independent predictors of mortality.

CONCLUSIONS

Both cellular and fibrosing ILD patterns are common among RA-ILD patients who undergo surgical lung biopsy. These patients have a shortened survival when compared to the general population and all-comers with RA. Age and the presence of a fibrosing interstitial pneumonia predict shortened survival in these patients. Survival in UIP is similar to matched IPF patients.

Selective inactivation of PTEN in smooth muscle cells synergizes with hypoxia to induce severe pulmonary hypertension

Background

Pulmonary vascular remodeling in pulmonary hypertension (PH) is characterized by increased vascular smooth muscle cell (SMC) and adventitial fibroblast proliferation, small vessel occlusion, and inflammatory cell accumulation. The underlying molecular mechanisms driving progression remain poorly defined. We have focused on loss of the phosphatase PTEN in SMCs as a major driver of pathological vascular remodeling. Our goal was to define the role of PTEN in human PH and in hypoxia‐induced PH using a mouse model with inducible deletion of PTEN in SMCs.

Methods and Results

Staining of human biopsies demonstrated enhanced inactive PTEN selectively in the media from hypertensive patients compared to controls. Mice with induced deletion of PTEN in SMCs were exposed to normoxia or hypoxia for up to 4 weeks. Under normoxia, SMC PTEN depletion was sufficient to induce features of PH similar to those observed in wild‐type mice exposed to chronic hypoxia. Under hypoxia, PTEN depletion promoted an irreversible progression of PH characterized by increased pressure, extensive pulmonary vascular remodeling, formation of complex vascular lesions, and increased macrophage accumulation associated with synergistic increases in proinflammatory cytokines and proliferation of both SMCs and nonSMCs.

Conclusions

Chronic inactivation of PTEN selectively in SMC represents a critical mediator of PH progression, leading to cell autonomous events and increased production of factors correlated to proliferation and recruitment of adventitial and inflammatory cells, resulting in irreversible progression of the disease.

Increased lymphatic vessel length is associated with the fibroblast reticulum and disease severity in usual interstitial pneumonia and nonspecific interstitial pneumonia

BACKGROUND

Lymphangiogenesis responds to tissue injury as a key component of normal wound healing. The development of fibrosis in the idiopathic interstitial pneumonias may result from abnormal wound healing in response to injury. We hypothesize that increased lymphatic vessel (LV) length, a marker of lymphangiogenesis, is associated with parenchymal components of the fibroblast reticulum (organizing collagen, fibrotic collagen, and fibroblast foci), and its extent correlates with disease severity.

METHODS

We assessed stereologically the parenchymal structure of fibrotic lungs and its associated lymphatic network, which was highlighted immunohistochemically in age-matched samples of usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP) with FVC &lt; 80%, COPD with a Global Initiative for Obstructive Lung Disease stage 0, and normal control lungs.

RESULTS

LV length density, as opposed to vessel volume density, was found to be associated with organizing and fibrotic collagen density (P &lt; .0001). Length density of LVs and the volume density of organizing and fibrotic collagen were significantly associated with severity of both % FVC (P &lt; .001) and diffusing capacity of the lung for carbon monoxide (P &lt; .001).

CONCLUSIONS

Severity of disease in UIP and NSIP is associated with increased LV length and is strongly associated with components of the fibroblast reticulum, namely organizing and fibrotic collagen, which supports a pathogenic role of LVs in these two diseases. Furthermore, the absence of definable differences between UIP and NSIP suggests that LVs are a unifying mechanism for the development of fibrosis in these fibrotic lung diseases.

MicroRNA-199a-5p is associated with hypoxia-inducible factor-1α expression in lungs from patients with COPD

BACKGROUND

MicroRNAs (miRNAs) are small noncoding RNAs that silence target gene expression posttranscriptionally, and their impact on gene expression has been reported in various diseases. It has been reported that the expression of the hypoxia-inducible factor-1α (HIF-1α) is reduced and that of p53 is increased in lungs from patients with COPD. However, the role of miRNAs associated with these genes in lungs from patients with COPD is unknown.

METHODS

Lung tissue samples from 55 patients were included in this study. Total RNA, miRNA, and protein were extracted from lung tissues and used for reverse transcriptase polymerase chain reaction and Western blot analysis. Cell culture experiments were performed using cultured human pulmonary microvascular endothelial cells (HPMVECs).

RESULTS

miR-34a and miR-199a-5p expressions were increased, and the phosphorylation of AKT was decreased in the lung tissue samples of patients with COPD. The miR-199a-5p expression was correlated with HIF-1α protein expression in the lungs of patients with COPD. Transfection of HPMVECs with the miR-199a-5p precursor gene decreased HIF-1α protein expression, and transfection with the miR-34a precursor gene increased miR-199a-5p expression.

CONCLUSIONS

These data suggest that miR-34a and miR-199a-5p contribute to the pathogenesis of COPD, and these miRNAs may also affect the HIF-1α-dependent lung structure maintenance program.

Familial Idiopathic Interstitial Pneumonia: Histopathology and Survival in 30 Patients

Context.—Familial idiopathic interstitial pneumonia (F-IIP) describes the unexplained occurrence of diffuse parenchymal lung disease in related individuals. Prevailing wisdom suggests that the histopathology of F-IIP is indistinguishable from that of idiopathic pulmonary fibrosis, namely, usual interstitial pneumonia (UIP).

Objective.—To define the histopathology of F-IIP in lung tissue samples.

Design.—Tissue sections from 30 patients with F-IIP, enrolled in a national research program, were evaluated by 3 pulmonary pathologists using 15 predefined histopathologic features. Each feature was recorded independently before a final diagnosis was chosen from a limited list dichotomized between UIP or “not UIP.” These 2 groups were then compared to survival.

Results.—The consensus diagnosis for the F-IIP cohort was an unclassifiable parenchymal fibrosis (60%), with a high incidence of histopathologic honeycombing, fibroblast foci, and smooth muscle in fibrosis. Usual interstitial pneumonia, strictly defined, was identified in less than half of the F-IIP cases (range, 23%–50%). Interobserver agreement was fair (κ  =  0.37) for 2 observers for the overall diagnosis of UIP. Findings unexpected in UIP were prevalent. The survival for the entire F-IIP cohort was poor, with an estimated mortality of 93% and a median age at death of 60.9 years. Subjects with UIP had a shorter survival and younger age at death.

Conclusions.—Pulmonary fibrosis was the dominant histopathology identified in our patients, but diagnostic features of UIP were seen in less than 50% of the samples. Overall survival was poor, with mortality accelerated apparently by the presence of a UIP pattern of disease.

Severe pulmonary arterial hypertension induced by SU5416 and ovalbumin immunization

The combination of chronic hypoxia and treatment of rats with the vascular endothelial growth factor (VEGF) receptor blocker, SU5416, induces pulmonary angio-obliteration, resulting in severe pulmonary arterial hypertension (PAH). Inflammation is thought to contribute to the pathology of PAH. Allergic inflammation caused by ovalbumin (OVA) immunization causes muscularization of pulmonary arteries, but not severe PAH. Whether disturbance of the immune system and allergic inflammation in the setting of lung endothelial cell apoptosis causes PAH is unknown. We investigated the effects of OVA-allergic inflammation on the development of PAH initiated by VEGF blockade-induced lung endothelial cell apoptosis. OVA-immunized rats were treated with SU5416 to induce pulmonary vascular endothelial cell apoptosis. The combination of OVA and SU5416 treatment resulted in severe angio-obilterative PAH, accompanied by increased IL-6 expression in the lungs. c-Kit(+) and Sca-1(+) cells were found in and around the lung vascular lesions. Pan-caspase inhibiton, dexamethasone treatment, and depletion of B-lymphocytes using an anti-CD20 antibody suppressed this remodeling. OVA immunization also increased lung tissue hypoxia-induced factor-1α and VEGF expression. Our results also suggest that the increased expression of hypoxia-induced factor-1α and IL-6 induced by the allergic lung inflammation may be a component of the pathogenesis of PAH.

Modern age pathology of pulmonary arterial hypertension

RATIONALE

The impact of modern treatments of pulmonary arterial hypertension (PAH) on pulmonary vascular pathology remains unknown.

OBJECTIVES

To assess the spectrum of pulmonary vascular remodeling in the modern era of PAH medication.

METHODS

Assessment of pulmonary vascular remodeling and inflammation in 62 PAH and 28 control explanted lungs systematically sampled.

MEASUREMENTS AND MAIN RESULTS

Intima and intima plus media fractional thicknesses of pulmonary arteries were increased in the PAH group versus the control lungs and correlated with pulmonary hemodynamic measurements. Despite a high variability of morphological measurements within a given PAH lung and among all PAH lungs, distinct pathological subphenotypes were detected in cohorts of PAH lungs. These included a subset of lungs lacking intima or, most prominently, media remodeling, which had similar numbers of profiles of plexiform lesions as those in lungs with more pronounced remodeling. Marked perivascular inflammation was present in a high number of PAH lungs and correlated with intima plus media remodeling. The number of profiles of plexiform lesions was significantly lower in lungs of male patients and those never treated with prostacyclin or its analogs.

CONCLUSIONS

Our results indicate that multiple features of pulmonary vascular remodeling are present in patients treated with modern PAH therapies. Perivascular inflammation may have an important role in the processes of vascular remodeling, all of which may ultimately lead to increased pulmonary artery pressure. Moreover, our study provides a framework to interpret and design translational studies in PAH.

Decreased neprilysin and pulmonary vascular remodeling in chronic obstructive pulmonary disease

RATIONALE

Studies with genetically engineered mice showed that decreased expression of the transmembrane peptidase neprilysin (NEP) increases susceptibility to hypoxic pulmonary vascular remodeling and hypertension; in hypoxic wild-type mice, expression is decreased early in distal pulmonary arteries, where prominent vascular remodeling occurs. Therefore, in humans with smoke- and hypoxia-induced vascular remodeling, as in chronic obstructive pulmonary disease (COPD), pulmonary activity/expression of NEP may likewise be decreased.

OBJECTIVES

To test whether NEP activity and expression are reduced in COPD lungs and pulmonary arterial smooth muscle cells (SMCs) exposed to cigarette smoke extract or hypoxia and begin to investigate mechanisms involved.

METHODS

Control and advanced COPD lung lysates (n = 13-14) were analyzed for NEP activity and protein and mRNA expression. As a control, dipeptidyl peptidase IV activity was analyzed. Lung sections were assessed for vascular remodeling and oxidant damage. Human pulmonary arterial SMCs were exposed to cigarette smoke extract, hypoxia, or H₂O₂, and incubated with antioxidants or lysosomal/proteasomal inhibitors.

MEASUREMENTS AND MAIN RESULTS

COPD lungs demonstrated areas of vascular rarification, distal muscularization, and variable intimal and prominent medial/adventitial thickening. NEP activity was reduced by 76%; NEP protein expression was decreased in alveolar walls and distal vessels; mRNA expression was also decreased. In SMCs exposed to cigarette smoke extract, hypoxia, and H₂O₂, NEP activity and expression were also reduced. Reactive oxygen species inactivated NEP activity; NEP protein degradation appeared to be substantially induced.

CONCLUSIONS

Mechanisms responsible for reduced NEP activity and protein expression include oxidative reactions and protein degradation. Maintaining or increasing lung NEP may protect against pulmonary vascular remodeling in response to chronic smoke and hypoxia.

Hypoxia inducible factor-1α in human emphysema lung tissue

The pathobiology of chronic obstructive pulmonary disease (COPD) is not completely understood. The aim of this study was to assess the expression of hypoxia inducible factor (HIF)-1α in lung tissue from patients with COPD/emphysema. Lung tissue samples from 26 patients were included in this study. Seven samples were obtained from patients with normal lung function, the remainder of the samples were taken from patients with moderate COPD (n = 6; stage I and II Global Initiative for Chronic Obstructive Lung Disease classification) and severe COPD (n = 13; stage III and IV). We analysed mRNA and protein expression in the lung tissue samples and found that: 1) HIF-1α and histone deacetylase 2 proteins were significantly decreased and were correlated; 2) HIF-1α and vascular endothelial growth factor (VEGF) proteins, and forced expiratory volume in 1 s % predicted were correlated in all patients; 3) the changes in VEGF and HIF-1α protein levels in all patients were not age-related and not related to the pack-yr smoking history; and 4) the reduced HIF-1α protein expression was seen in lung endothelial cells and alveolar septal cells by immunohistochemistry. In conclusion, reduced expression of HIF-1α protein in severe COPD is consistent with the concept of a lung structure maintenance programme which is impaired on a molecular level.

Formation of plexiform lesions in experimental severe pulmonary arterial hypertension

BACKGROUND

The plexiform lesion is the hallmark of severe pulmonary arterial hypertension. However, its genesis and hemodynamic effects are largely unknown because of the limited availability of lung tissue samples from patients with pulmonary arterial hypertension and the lack of appropriate animal models. This study investigated whether rats with severe progressive pulmonary hypertension developed plexiform lesions.

METHODS AND RESULTS

After a single subcutaneous injection of the vascular endothelial growth factor receptor blocker Sugen 5416, rats were exposed to hypoxia for 3 weeks. They were then returned to normoxia for an additional 10 to 11 weeks. Hemodynamic and histological examinations were performed at 13 to 14 weeks after the Sugen 5416 injection. All rats developed pulmonary hypertension (right ventricular systolic pressure approximately 100 mm Hg) and severe pulmonary arteriopathy, including concentric neointimal and complex plexiform-like lesions. There were 2 patterns of complex lesion formation: a lesion forming within the vessel lumen (stalk-like) and another that projected outside the vessel (aneurysm-like). Immunohistochemical analyses showed that these structures had cellular and molecular features closely resembling human plexiform lesions.

CONCLUSIONS

Severe, sustained pulmonary hypertension in a very late stage of the Sugen 5416/hypoxia/normoxia-exposed rat is accompanied by the formation of lesions that are indistinguishable from the pulmonary arteriopathy of human pulmonary arterial hypertension. This unique model provides a new and rigorous approach for investigating the genesis, hemodynamic effects, and reversibility of plexiform and other occlusive lesions in pulmonary arterial hypertension.

Murine gammaherpesvirus 68 infection of IFNgamma unresponsive mice: a small animal model for gammaherpesvirus-associated B-cell lymphoproliferative disease

Gammaherpesviruses are tightly controlled by the host immune response, with gammaherpesvirus-associated malignancies prevalent in immune-suppressed individuals. Previously, infection of IFNgamma-unresponsive mice with gammaherpesvirus 68 (gammaHV68) showed that IFNgamma controlled chronic infection, limiting chronic diseases including arteritis and pulmonary fibrosis. Here, we show that gammaHV68-infected IFNgamma receptor-deficient (IFNgammaR(-/-)) mice uniformly develop angiocentric inflammatory lesions in the lung. Prolonged infection revealed a range of outcomes, from spontaneous regression to pulmonary lymphoma. By 12 months of infection, 80% of mice had lymphoid hyperplasia or pulmonary lymphoma; 45% of infected mice developed frank tumors between 5 and 12 months postinfection, with some mice showing systemic involvement. Lymphomas were composed of B lymphocytes and contained latently infected cells. Although IFNgammaR(-/-) mice control chronic gammaHV68 infection poorly, both early and late pathologies were indistinguishable between wild-type and reactivation-defective virus infection, indicating that, in contrast with other previously described gammaHV68-associated pathologies, these chronic diseases were not dependent on the reactivation of latent infection. This distinct combination of latent infection and defined host defect led to a specific and consistent lymphoproliferative disease. Significantly, this mouse model of virus-associated pulmonary B-cell lymphoma closely mimics the full spectrum of human lymphomatoid granulomatosis, an EBV-associated malignancy with no effective treatment.