Genetic predisposition to respiratory diseases: infiltrative lung diseases

Destructive fibrotic teamwork: how both microenvironment stiffness and profibrotic interleukin 13 impair alveolar macrophage phenotype and function

The pulmonary fibrotic microenvironment is characterized by increased stiffness of lung tissue and enhanced secretion of profibrotic soluble cues contributing to a feedback loop that leads to dysregulated wound healing and lung failure. Pinpointing the individual and tandem effects of profibrotic stimuli in impairing immune cell response remains difficult and is needed for improved therapeutic strategies. We utilized a statistical design of experiment (DOE) to investigate how microenvironment stiffness and interleukin 13 (IL13), a profibrotic soluble factor linked with disease severity, contribute to the impaired macrophage response commonly observed in pulmonary fibrosis. We used engineered bioinspired hydrogels of different stiffness, ranging from healthy to fibrotic lung tissue, and cultured murine alveolar macrophages (MH-S cells) with or without IL13 to quantify cell response and analyze independent and synergistic effects. We found that, while both stiffness and IL13 independently influence macrophage morphology, phenotype, phagocytosis and efferocytosis, these factors work synergistically to exacerbate impaired macrophage phenotype and efferocytosis. These unique findings provide insights into how macrophages in fibrotic conditions are not as effective in clearing debris, contributing to fibrosis initiation/progression, and more broadly inform how underlying drivers of fibrosis modulate immune cell response to facilitate therapeutic strategies.

Correlating SFTPC gene variants to interstitial lung disease in Egyptian children

Background

Interstitial lung disease (ILD) is a broad heterogeneous group of lung disorders that is characterized by inflammation of the lungs. Surfactant dysfunction disorders are a rare form of ILD diseases that result from mutations in surfactant protein C gene (SFTPC) with prevalence of approximately 1/1.7 million births. SFTPC patients are presented with clinical manifestations of ILD ranging from fatal respiratory failure of newborn to chronic respiratory problems in children. In the current study, we aimed to investigate the spectrum of SFTPC genetic variants as well as the correlation of the SFTPC gene mutations with ILD disease in twenty unrelated Egyptian children with diffuse lung disease and suspected surfactant dysfunction using Sanger sequencing.

Results

Sequencing of SFTPC gene revealed five variants: c.42+35G>A (IVS1+35G>A) (rs8192340) and c.43-21T>C (IVS1-21T>C) (rs13248346) in intron 1, c.436-8C>G (IVS4-8C>G) (rs2070687) in intron 4, c.413C>A p.T138N (rs4715) in exon 4, and c.557G>Ap.S186N (rs1124) in exon 5.

Conclusion

The present study confirms the association of detecting variants of SFTPC with surfactant dysfunction disorders.

Molecular pathways and role of epigenetics in the idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease with unknown etiological factors that can progress to other dangerous diseases like lung cancer. Environmental and genetic predisposition are the two major etiological or risk factors involved in the pathology of the IPF. Among the environmental risk factors, smoking is one of the major causes for the development of IPF. Epigenetic pathways like nucleosomes remodeling, DNA methylation, histone modifications and miRNA mediated genes play a crucial role in development of IPF. Mutations in the genes make the epigenetic factors as important drug targets in IPF. Transcriptional changes due to environmental factors are also involved in the progression of IPF. The mutations in human telomerase reverse transcriptase (hTERT) have shown decreased life expectancy in IPF patients. The TERT-gene is highly expressed in chronic smokers and makes the role of epigenetics evident. Drug like nintedanib acts through vascular endothelial growth factor receptors (VEGFR), while drug pirfenidone acts through transforming growth factor (TGF), which is useful in IPF. Gefitinib, a tyrosine kinase inhibitor of EGFR, is useful as an anti-fibrosis agent in preclinical models. Newer drugs such as Celgene-CC90001 and FibroGen-FG-3019 are currently under investigations acts through the modulating epigenetic mechanisms. Thus, the study on epigenetics opens a wide window for the discovery of newer drugs. This study provides an elementary analysis of multiple regulators of epigenetics and their roles associated with the pathology of IPF. Further, this review also includes epigenetic drugs under development in preclinical and clinical stages.

Structural alteration of lung parenchyma in patients with NF1: a phenotyping study using multidetector computed tomography (MDCT)

BACKGROUND

Diffuse interstitial lung disease have been described in Neurofibromatosis type 1 (NF1), but its diversity and prevalence remain unknown. The aim of this study was to assess the prevalence and characteristics of (NF1)-associated lung manifestations in a large single-center study using multidetector computed tomography (MDCT) and to evaluate the smoking history, patients' age, genetics, and the presence of malignant peripheral nerve sheath tumors (MPNST) as potential influencing factors for lung pathologies.

METHODS

In this retrospective study, 71 patients with NF1 were evaluated for the presence of distinctive lung manifestations like reticulations, consolidations, type of emphysema, pulmonary nodules and cysts. All patients underwent F-18-FDG PET/CT scans, which were reviewed by two experienced radiologists in consensus. Patients' subgroups were formed based on their smoking history (current smokers/previous smokers/never smokers), age (< 12 years, 12-18 years, > 18 years), and presence of MPNST (MPNST/no MPNST). In 57 patients (80%), genetic analysis of sequences coding for the neurofibromin on chromosome 17 was performed, which was correlated with different lung pathologies.

RESULTS

Among all NF1 patients (33 ± 14 years, 56% females), 17 patients (24%) were current smokers and 62 patients (87%) were > 18 years old. Pulmonary cysts, nodules, and paraseptal emphysema were the most common pulmonary findings (35%, 32%, 30%). The presence of pulmonary metastases, MPNST and centrilobular emphysema was associated with smoking. Cysts were observed only in adults, whereas no significant correlation between age and all other pulmonary findings was found (p > 0.05). Presence of MPNST was accompanied by higher rates of intrapulmonary nodules and pulmonary metastasis. Neither the presence nor absence of any of the specific gene mutations was associated with any particular lung pathology (p > 0.05).

CONCLUSIONS

All pulmonary findings in NF1 patients occurred independently from specific mutation subtypes, suggesting that many NF1 mutations can cause various pulmonary pathologies. The presence of pulmonary metastases, MPNST and centrilobular emphysema was associated with smoking, indicating the value of smoking secession or the advice not to start smoking in NF1 patients as preventive strategy for clinicians. For screening of pulmonary manifestations in NF1 patients, an MDCT besides medical history and physical examination is mandatory in clinical routine.

Ocular Sarcoidosis

Sarcoidosis is one of the leading causes of inflammatory eye disease. Any part of the eye and its adnexal tissues can be involved. Uveitis and optic neuropathy are the main manifestations, which may require systemic treatment. Two groups of patients with sarcoid uveitis can be distinguished: one of either sex and any ethnicity in which ophthalmological findings are various and another group of elderly Caucasian women with mostly chronic posterior uveitis. Clinically isolated uveitis revealing sarcoidosis remains a strictly ocular condition in a large majority of cases. Although it can be a serious condition involving functional prognosis, early recognition in addition to a growing therapeutic arsenal (including intravitreal implant) has improved the visual prognosis of the disease in recent years. Systemic corticosteroids are indicated when uveitis does not respond to topical corticosteroids or when there is bilateral posterior involvement, especially macular edema. In up to 30% of the cases that require an unacceptable dosage of corticosteroids to maintain remission, additional immunosuppression is used, especially methotrexate. As with other forms of severe noninfectious uveitis, monoclonal antibodies against tumor necrosis factor-α have been used. However, only very rarely does sarcoid uveitis fail to respond to combined corticosteroids and methotrexate therapy, a situation that should suggest either poor adherence or another granulomatous disease. Optic neuropathy often affects women of African and Caribbean origins. Some authors recommend that patients should be treated with high-dose of corticosteroids and concurrent immunosuppression from the onset of this manifestation, which is associated with a poorer outcome.

Epidermal growth factor receptor (EGFR) pathway genes and interstitial lung disease: an association study

The etiology and pathogenesis of idiopathic interstitial lung disease (ILD) remain incompletely understood. Genetic susceptibility to ILD has been demonstrated in previous studies. It is well known that EGFR inhibitors can induce ILD in human lung cancer patient with ethnic differences, which prompted us to hypothesize that genetic variation in EGFR pathway genes confer susceptibility to ILD. We aimed in this study to investigate whether functional polymorphisms of EGFR and its ligands genes (EGF and TGFA) were associated with ILD. Three EGFR [-216G/T (rs712830), -191A/C (rs712829), 497R > K(A/G) (rs2227983)], one EGF [61A/G, (rs4444903)] and one TGFA (rs3821262C/T) polymorphisms previously demonstrated to alter gene functions were genotyped in 229 sporadic idiopathic ILD patients and 693 normal healthy individuals. Allelic and genotypic association tests between these polymorphisms and ILD were performed. The EGF 61A/G polymorphism was significantly associated with elevated risk of ILD, with the frequency of G allele significantly increased in the ILD patient population (OR = 1.33, 95%CI = 1.07-1.66, P = 0.0099). None of the other polymorphisms were associated with risk of ILD. Our study suggested that the EGF 61A/G polymorphism may be associated with sporadic ILD. While a false positive finding cannot be excluded, independent studies are warranted to further validate this result.

Genetic testing in diffuse parenchymal lung disease

Diffuse parenchymal lung diseases (DPLD) represent a diverse group of disorders affecting the distal lung parenchyma, specifically the tissue and spaces surrounding the alveoli, which may be filled with inflammatory cells, proliferating fibroblasts or established fibrosis, often leading to architectural distortion and impaired gas exchange. While the underlying pathogenetic mechanisms are known or inferred for some DPLD (such as sarcoidosis, silicosis, drug reactions and collagen vascular diseases), the pathogenesis of the majority of these entities - particularly those characterized by progressive fibrosis - is poorly understood.

Several lines of evidence indicate that the development of pulmonary fibrosis is genetically determined. They include: 1. familial clustering; 2. the occurrence of pulmonary fibrosis in the context of rare inherited disorders; 3. substantial variability in the development of pulmonary fibrosis amongst individuals exposed to organic or inorganic dusts; 4. difference in susceptibility to fibrogenic stimuli amongst inbred strains of mice.

This review focuses on idiopathic pulmonary fibrosis (IPF) and sarcoidosis, the two most common DPLD and the two entities for which there is stronger evidence of a genetic predisposition, although how aberrant genes interact with each other and with environmental factors, such as smoking in IPF and infectious agents in sarcoidosis, in determining disease susceptibility and clinical phenotypes is largely unknown. Finally, we discuss practical issues and implications for both patients and physicians of recent advances in the genetics of sarcoidosis and IPF.

Idiopathic pulmonary fibrosis may be a disease of recurrent, tractional injury to the periphery of the aging lung: a unifying hypothesis regarding etiology and pathogenesis

CONTEXT

Idiopathic pulmonary fibrosis is a progressive, fatal lung disease occurring in older individuals. Despite 50 years of accrued data about the disease, little progress has been made in slowing functional loss or in decreasing patient mortality.

OBJECTIVE

To present a novel hypothesis on the etiology and pathogenesis of idiopathic pulmonary fibrosis.

DESIGN

Published data are reviewed regarding the epidemiology, clinical presentation, natural history, radiologic findings, and pathologic findings in patients with idiopathic pulmonary fibrosis.

RESULTS

Patients with idiopathic pulmonary fibrosis may be predisposed genetically to tractional injury to the peripheral lung. The result is recurrent damage to the epithelial-mesenchymal interface, preferentially at the outer edges of the basilar lung lobules where tractional stress is high during inspiration, compliance is relatively low, and there is a greater tendency for alveolar collapse at end-expiration. A distinctive "reticular network of injury" (the fibroblast focus) forms, attended by a prolonged phase of wound repair (tear and slow repair). Discrete areas of alveolar collapse are observed in scar at the periphery of the lung lobules. The cycle repeats over many years resulting in progressive fibrous remodeling and replacement of the alveoli in a lobule by bronchiolar cysts surrounded by scar (honeycomb lung). Abnormalities in surfactant function are proposed as a potential mechanism of initial lung damage. Age of onset may be a function of a required threshold of environmental exposures (eg, cigarette smoking) or other comorbid injury to the aging lung.

CONCLUSIONS

Evidence supporting this hypothesis is presented and potential mechanisms are discussed. A potential role for contributing cofactors is presented.

Familial pulmonary fibrosis is the strongest risk factor for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disorder of unknown etiology. The disease is likely the result of complex interactions between genetic and environmental factors. Evidence suggests that certain environmental factors, such as cigarette smoking and metal dust exposures, or comorbidities like gastroesophageal reflux, and type 2 diabetes mellitus (DM2) may increase risk to develop IPF. Substantial uncertainty remains, however, regarding these and other putative risk factors for IPF. In this study we performed a case-control analysis including 100 patients with IPF and 263 controls matched for age sex and place of residence. We used a structured questionnaire to identify potential risk factors for IPF, including environmental and occupational exposures as well as the relevance of family history of pulmonary fibrosis. The multivariate analysis revealed that family history of pulmonary fibrosis [OR = 6.1, CI95% 2.3-15.9; p < 0.0001] was strongly associated with increased risk of IPF. Actually, 20% of the cases reported a parent or sibling with pulmonary fibrosis. Gastroesophageal reflux [OR = 2.9, CI: 1.3-6.6; p = 0.007], former cigarette smoking [OR = 2.5, CI: 1.4-4.6, p = 0.003], and past or current occupational exposure to dusts, smokes, gases or chemicals [OR = 2.8, CI: 1.5-5.5; p = 0.002] were also associated with the disease. Despite being a significant risk factor on univariate analysis DM2 was not significant in multivariate analysis. These findings indicate that family history of pulmonary fibrosis is a strong risk factor for IPF. Also, we confirmed that occupational exposures, gastroesophageal reflux and former smoking increase the risk for this disease.

Chronic obstructive pulmonary disease-specific gene expression signatures of alveolar macrophages as well as peripheral blood monocytes overlap and correlate with lung function

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease characterized by progressive airflow limitation and significant extrapulmonary (systemic) effects that lead to co-morbid conditions, though the pathomechanism of COPD is largely undetermined. Alveolar macrophages (AM) derived from peripheral monocytes (MO) appear to play a key role in initiating and/or sustaining disease progression.

OBJECTIVES

To identify disease- and cell type-specific gene expression profiles and potential overlaps in those in order to diagnose COPD, characterize its progression and determine the effect of drug treatment.

METHOD

Global gene expression analysis was used for primary screening in order to obtain expression signatures of AMs and circulating MOs of COPD patients and healthy controls. The results of microarray analyses of AMs (20 controls and 26 COPD patients) and MOs (16 controls and 22 COPD patients) were confirmed and validated by real-time quantitative polymerase chain reaction.

RESULTS

We have identified gene sets specifically associated with COPD in AMs and MOs. There were overlapping genes between the two cell types. Our data also show that COPD-specific gene expression signatures in AMs and MOs correlate with percent of predicted FEV(1).

CONCLUSION

Disease-specific and overlapping gene expression signatures can be defined in lung-derived macrophages and also in circulating monocytes. Some of the validated expression changes in both cell types correlate with lung function and therefore could serve as biomarkers of disease progression.

Copy number variation of FCGR3B is associated with susceptibility to idiopathic pulmonary fibrosis

BACKGROUND

Several genes exhibit copy number variation (CNV), including FCGR3B which encodes the IgG receptor FcγRIIIb. Engagement of Fcγ receptors by IgG complexes may contribute to the pathogenesis of idiopathic pulmonary fibrosis (IPF).

OBJECTIVES

To investigate whether FCGR3B CNV is associated with susceptibility to IPF.

METHODS

In a case-control study we compared FCGR3B copy number in 142 patients with IPF and in 221 controls by real-time quantitative PCR using CD36 as gene copy control.

RESULTS

Significantly increased FCGR3B:CD36 ratio was evident in the IPF cohort compared to controls (p = 0.009). Association of FCGR3B copy number with IPF susceptibility was further confirmed by a likelihood ratio statistical approach (p = 0.003). FCGR3B copy number assignment based on FCGR3B:CD36 ratios revealed significant skewing in the distribution of FCGR3B copy number between IPF patients and controls. In the IPF cohort, there was increased frequency of >2 FCGR3B copies compared to controls (0.30 vs. 0.19; χ(2) = 9.27; d.f. 2; p = 0.0097). The presence of >2 FCGR3B copies was associated with higher risk of IPF (p = 0.01, OR: 1.914, 95% CI: 1.17-3.12).

CONCLUSIONS

These findings support an association of FCGR3B copy number with susceptibility to IPF and propose a novel role for Fcγ receptors in IPF disease pathogenesis.

Metallic elements in exhaled breath condensate of patients with interstitial lung diseases

Epidemiological data support the hypothesis that environmental and occupational agents play an important role in the development of interstitial lung diseases such as idiopathic interstitial pneumonia (IIPs) and sarcoidosis. The aim of this study was to assess the elemental composition of exhaled breath condensate (EBC) in patients with interstitial lung diseases (ILDs) of unknown etiology and healthy subjects as an indirect evaluation of tissue burden, which could improve our understanding of the role of metals in the pathogenesis of ILDs. EBC was obtained from 33 healthy subjects, 22 patients with sarcoidosis, 15 patients with non-specific interstitial pneumonia (NSIP) and 19 with IIPs. Trace elements and toxic metals in the samples were measured by means of inductively coupled plasma-mass spectrometry. There are only small overall differences in the EBC levels of a number of metallic elements among patients with idiopathic pulmonary fibrosis (IPF), NSIP or sarcoidosis, and no pattern is capable of distinguishing them with a high degree of sensitivity and specificity. However, a pattern of pneumotoxic (Si, Ni) and essential elements (Zn, Se and Cu) with the addition of Co distinguished the patients with ILDs from healthy non-smokers with relatively high degrees of sensitivity (96.4%) and specificity (90.9%). Assessing the elemental composition of EBC in patients with different ILDs seems to provide useful information. The non-invasiveness of the EBC method makes it suitable for patients with pulmonary diseases, although further studies are required to confirm the usefulness of this approach and to better understand the underlying pathophysiological processes.

TLR4 is essential in acute lung injury induced by unresuscitated hemorrhagic shock

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome in patients with hemorrhagic shock (HS) or resuscitation is associated with the expression of TLR4. However, the role of TLR4 in ALI induced by unresuscitated HS remains obscure.

METHODS

The lung pathologic change was observed by hematoxylin and eosin staining. Interleukin-1beta and tumor necrosis factor-alpha were analyzed by enzyme-linked immunosorbent assay. Polymorphonuclear leukocyte sequestration and lung leak were analyzed by pulmonary myeloperoxidase activity and Evans blue dye. The expressions of TLR4 mRNA and protein were analyzed by reverse transcription-polymerase chain reaction and Western blot, respectively. TLR4 distribution was analyzed by immunohistochemistry.

RESULTS

Lung neutrophil accumulation and microvascular permeability were significantly increased after unresuscitated HS, meanwhile, lung interleukin-1beta and tumor necrosis factor-alpha were gradually augmented. TLR4 mRNA, TLR4 distribution and TLR4 protein were also significantly increased in TLR4 wt mice, however, no above-mentioned changes appeared in TLR4 mutant mice.

CONCLUSIONS

TLR4 is strongly associated with the pathogenesis of ALI induced by unresuscitated HS, which may serve as a useful therapeutic target.

Therapies for interstitial lung disease: past, present and future

As our understanding of the pathobiology and natural history of the various forms of interstitial lung disease (ILD) has evolved, so have our approaches to treating this heterogeneous group of lung disorders. The earliest pharmacologic agents used to treat various forms of ILD were corticosteroids, and corticosteroids are currently the mainstay of therapy for many forms of ILD. However, it has become clear that corticosteroids and other anti-inflammatory agents lack efficacy for many forms of ILD, such as idiopathic pulmonary fibrosis (IPF), and newer therapies that are in clinical trials target the fibrogenic process and/or secondary pulmonary hypertension (PH) that is present in various forms of fibrotic lung disease. Novel therapies, such as the use of biologic agents (antibodies and cell cycle inhibitors) or stem cell therapies will undoubtedly evolve as new research is performed and clinical trials are undertaken. Lung transplantation remains an option for advanced lung disease that is progressive and unresponsive to non-surgical therapies.