Future research directions in idiopathic pulmonary fibrosis: summary of a National Heart, Lung, and Blood Institute working group

Single Cell Transcriptome Signatures of Sarcoidosis in Lung Immune Cell Populations

Rationale

To identify cell specific molecular changes associated with sarcoidosis risk and progression, we aimed to characterize the cellular composition, gene expression patterns, and cell-cell interactions in BAL cells from patients with sarcoidosis (both progressive and non-progressive) and healthy controls.

Methods

Single cell RNA-seq data were collected on 12 sarcoidosis and 4 control participants. We combined scRNA-seq data from these participants with our previously collected data on 4 sarcoidosis and 10 control participants for a final sample size of 16 sarcoidosis cases (8 progressive and 8 non-progressive) and 14 controls. Following initial preprocessing in CellRanger, data were quality controlled, combined, and clustered in Seurat. We tested differences in cell proportions by disease group using F-tests on cell proportions and differences in gene expression using pseudobulk analysis. Cell to cell communication and pathway analysis were performed using CellChat.

Results

We identified five macrophage populations: resident, high metallothionein (MT) resident, recruited, profibrotic recruited, and proliferating macrophages. Each subpopulation displayed unique gene expression profiles, with notable differential expression of genes and pathways linked to sarcoidosis in resident macrophages, recruited macrophages, and proliferating macrophages. We also observed changes in gene expression associated with disease progression in resident and recruited macrophages. In non-macrophages cells, we observed a significant reduction in the number of B cells in sarcoidosis patients compared to controls. Among T cell populations, we identified specific transcriptional alterations at gene and pathway level. Additionally, we observed distinct differences in cell-to-cell interactions of macrophages and T cells between sarcoidosis patients and healthy controls.

Conclusions

These findings underscore the complexity of immune cell involvement in sarcoidosis and highlight potential cellular and molecular targets for further investigation.

Phytochemical Compounds as Promising Therapeutics for Intestinal Fibrosis in Inflammatory Bowel Disease: A Critical Review

BACKGROUND/OBJECTIVE

Intestinal fibrosis, a prominent consequence of inflammatory bowel disease (IBD), presents considerable difficulty owing to the absence of licensed antifibrotic therapies. This review assesses the therapeutic potential of phytochemicals as alternate methods for controlling intestinal fibrosis. Phytochemicals, bioactive molecules originating from plants, exhibit potential antifibrotic, anti-inflammatory, and antioxidant activities, targeting pathways associated with inflammation and fibrosis. Compounds such as Asperuloside, Berberine, and olive phenols have demonstrated potential in preclinical models by regulating critical signaling pathways, including TGF-β/Smad and NFκB, which are integral to advancing fibrosis.

RESULTS

The main findings suggest that these phytochemicals significantly reduce fibrotic markers, collagen deposition, and inflammation in various experimental models of IBD. These phytochemicals may function as supplementary medicines to standard treatments, perhaps enhancing patient outcomes while mitigating the adverse effects of prolonged immunosuppressive usage. Nonetheless, additional clinical trials are necessary to validate their safety, effectiveness, and bioavailability in human subjects.

CONCLUSIONS

Therefore, investigating phytochemicals may lead to crucial advances in the formulation of innovative treatment approaches for fibrosis associated with IBD, offering a promising avenue for future therapeutic development.

Suppression of OGN in lung myofibroblasts attenuates pulmonary fibrosis by inhibiting integrin αv-mediated TGF-β/Smad pathway activation

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) represents a severe and progressive manifestation of idiopathic interstitial pneumonia marked by an uncertain etiology along with an unfavorable prognosis. Osteoglycin (OGN), belonging to the small leucine-rich proteoglycans family, assumes pivotal functions in both tissue formation and damage response. However, the roles and potential mechanisms of OGN in the context of lung fibrosis remain unexplored.

METHODS

The assessment of OGN expression levels in fibrotic lungs was conducted across various experimental lung fibrosis mouse models. To elucidate the effects of OGN on the differentiation of lung myofibroblasts, both OGN knockdown and OGN overexpression were employed in vitro. The expression of integrin αv, along with its colocalization with lysosomes and latency-associated peptide (LAP), was monitored in OGN-knockdown lung myofibroblasts. Furthermore, the role of OGN in lung fibrosis was investigated through OGN knockdown utilizing adeno-related virus serotype 6 (AAV6)-mediated delivery.

RESULTS

OGN exhibited upregulation in both lungs and myofibroblasts across diverse lung fibrosis mouse models. And laboratory experiments in vitro demonstrated that OGN knockdown inhibited the TGF-β/Smad signaling pathway in lung myofibroblasts. Conversely, OGN overexpression promoted TGF-β/Smad pathway in these cells. Mechanistic insights revealed that OGN knockdown facilitated lysosome-mediated degradation of integrin αv while inhibiting its binding to latency-associated peptide (LAP). Remarkably, AAV6-targeted OGN knockdown ameliorated the extent of lung fibrosis in experimental mouse models.

CONCLUSION

Our results indicate that inhibiting OGN signaling could serve as a promising therapeutic way for lung fibrosis.

Insights into Disease Progression of Translational Preclinical Rat Model of Interstitial Pulmonary Fibrosis through Endpoint Analysis

Idiopathic pulmonary fibrosis (IPF) is a devastating interstitial lung disease characterized by the relentless deposition of extracellular matrix (ECM), causing lung distortions and dysfunction. Animal models of human IPF can provide great insight into the mechanistic pathways underlying disease progression and a means for evaluating novel therapeutic approaches. In this study, we describe the effect of bleomycin concentration on disease progression in the classical rat bleomycin model. In a dose-response study (1.5, 2, 2.5 U/kg i.t), we characterized lung fibrosis at day 14 after bleomycin challenge using endpoints including clinical signs, inflammatory cell infiltration, collagen content, and bronchoalveolar lavage fluid-soluble profibrotic mediators. Furthermore, we investigated fibrotic disease progression after 2 U/kg i.t. bleomycin administration at days 3, 7, and 14 by quantifying the expression of clinically relevant signaling molecules and pathways, epithelial mesenchymal transition (EMT) biomarkers, ECM components, and histopathology of the lung. A single bleomycin challenge resulted in a progressive fibrotic response in rat lung tissue over 14 days based on lung collagen content, histopathological changes, and modified Ashcroft score. The early fibrogenesis phase (days 3 to 7) is associated with an increase in profibrotic mediators including TGFβ1, IL6, TNFα, IL1β, CINC1, WISP1, VEGF, and TIMP1. In the mid and late fibrotic stages, the TGFβ/Smad and PDGF/AKT signaling pathways are involved, and clinically relevant proteins targeting galectin-3, LPA1, transglutaminase-2, and lysyl oxidase 2 are upregulated on days 7 and 14. Between days 7 and 14, the expressions of vimentin and α-SMA proteins increase, which is a sign of EMT activation. We confirmed ECM formation by increased expressions of procollagen-1Aα, procollagen-3Aα, fibronectin, and CTGF in the lung on days 7 and 14. Our data provide insights on a complex network of several soluble mediators, clinically relevant signaling pathways, and target proteins that contribute to drive the progressive fibrotic phenotype from the early to late phase (active) in the rat bleomycin model. The framework of endpoints of our study highlights the translational value for pharmacological interventions and mechanistic studies using this model.

Targeting ATP12A, a Nongastric Proton Pump α Subunit, for Idiopathic Pulmonary Fibrosis Treatment

Idiopathic pulmonary fibrosis (IPF) is a pathological condition of unknown etiology that results from injury to the lung and an ensuing fibrotic response that leads to the thickening of the alveolar walls and obliteration of the alveolar space. The pathogenesis is not clear, and there are currently no effective therapies for IPF. Small airway disease and mucus accumulation are prominent features in IPF lungs, similar to cystic fibrosis lung disease. The ATP12A gene encodes the α-subunit of the nongastric H+, K+-ATPase, which functions to acidify the airway surface fluid and impairs mucociliary transport function in patients with cystic fibrosis. It is hypothesized that the ATP12A protein may play a role in the pathogenesis of IPF. The authors' studies demonstrate that ATP12A protein is overexpressed in distal small airways from the lungs of patients with IPF compared with normal human lungs. In addition, overexpression of the ATP12A protein in mouse lungs worsened bleomycin induced experimental pulmonary fibrosis. This was prevented by a potassium competitive proton pump blocker, vonoprazan. These data support the concept that the ATP12A protein plays an important role in the pathogenesis of lung fibrosis. Inhibition of the ATP12A protein has potential as a novel therapeutic strategy in IPF treatment.

Persistent changes in expression of genes involved in inflammation and fibrosis in the lungs of rats exposed to airborne lunar dust

NASA is currently planning return missions to the Moon for further exploration and research. The Moon is covered by a layer of potentially reactive fine dust, which could pose a toxicological risk of exposure to explorers. To assess this risk, we exposed rats to lunar dust (LD) that was collected during the Apollo14 mission. Rats were exposed to respirable sizes of LD at concentrations of 0, 2.1, 6.8, 20.8, or 60.6 mg/m³ for 4 weeks. One day, and one, four, and thirteen  weeks after exposure, we assessed 44,000 gene transcripts and found the expression of 614 genes with known functions were significantly altered in the rats exposed to the 2 higher concentrations of LD, whereas few changes in gene expression were detected in the group exposed to the lowest concentration of LD. Many of the significant changes in gene expression involved genes known to be associated with inflammation or fibrosis. Four genes encoding pro-inflammatory chemokines were analyzed further using real-time polymerase chain reaction. The expression of these genes was altered in a dose- and time-dependent manner and persistently changed in the lungs of the rats exposed to the two higher concentrations of LD. Their expressions are consistent with changes we detected in pulmonary toxicity biomarkers and pathology in these animals during a previous study. Because Apollo-14 LD contains common mineral oxides similar to an Arizona volcanic ash, besides revealing the toxicity of LD, our findings could help elucidate the genomic and molecular mechanisms involved in pulmonary toxicity induced by terrestrial mineral dusts.

Bone morphogenetic protein 4 inhibits pulmonary fibrosis by modulating cellular senescence and mitophagy in lung fibroblasts

BACKGROUND

Accumulation of myofibroblasts is critical to fibrogenesis in idiopathic pulmonary fibrosis (IPF). Senescence and insufficient mitophagy in fibroblasts contribute to their differentiation into myofibroblasts, thereby promoting the development of lung fibrosis. Bone morphogenetic protein 4 (BMP4), a multifunctional growth factor, is essential for the early stage of lung development; however, the role of BMP4 in modulating lung fibrosis remains unknown.

METHODS

The aim of this study was to evaluate the role of BMP4 in lung fibrosis using BMP4-haplodeleted mice, BMP4-overexpressed mice, primary lung fibroblasts and lung samples from patients with IPF.

RESULTS

BMP4 expression was downregulated in IPF lungs and fibroblasts compared to control individuals, negatively correlated with fibrotic genes, and BMP4 decreased with transforming growth factor (TGF)-β1 stimulation in lung fibroblasts in a time- and dose-dependent manner. In mice challenged with bleomycin, BMP4 haploinsufficiency perpetuated activation of lung myofibroblasts and caused accelerated lung function decline, severe fibrosis and mortality. BMP4 overexpression using adeno-associated virus 9 vectors showed preventative and therapeutic efficacy against lung fibrosis. In vitro, BMP4 attenuated TGF-β1-induced fibroblast-to-myofibroblast differentiation and extracellular matrix (ECM) production by reducing impaired mitophagy and cellular senescence in lung fibroblasts. Pink1 silencing by short-hairpin RNA transfection abolished the ability of BMP4 to reverse the TGF-β1-induced myofibroblast differentiation and ECM production, indicating dependence on Pink1-mediated mitophagy. Moreover, the inhibitory effect of BMP4 on fibroblast activation and differentiation was accompanied with an activation of Smad1/5/9 signalling and suppression of TGF-β1-mediated Smad2/3 signalling in vivo and in vitro.

CONCLUSION

Strategies for enhancing BMP4 signalling may represent an effective treatment for pulmonary fibrosis.

MicroSPECT Imaging-Guided Treatment of Idiopathic Pulmonary Fibrosis in Mice with a Vimentin-Targeting 99mTc-Labeled N-Acetylglucosamine-Polyethyleneimine

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic disease with poor prognosis. Evidence has shown that vimentin is a key regulator of lung fibrogenesis. ^99mTc-labeled N-acetylglucosamine-polyethyleneimine (NAG-PEI), a vimentin-targeting radiotracer, was used for the early diagnosis of IPF, and NAG-PEI was also used as a therapeutic small interfering RNA (siRNA) delivery vector for the treatment of IPF in this study. Single-photon emission-computed tomography (SPECT) imaging of bleomycin (BM)- and silica-induced IPF mice with ^99mTc-labeled NAG-PEI was performed to visualize pulmonary fibrosis and monitor the treatment efficiency of siRNA-loaded NAG-PEI, lipopolysaccharide (LPS, a tolerogenic adjuvant), or zymosan (ZYM, an immunostimulant). The lung uptakes of ^99mTc-NAG-PEI in the BM- and silica-induced IPF mice were clearly and directly correlated with IPF progression. The lung uptake of ^99mTc-NAG-PEI in the NAG-PEI/TGF-β1-siRNA treatment group or LPS treatment group was evidently lower than that in the control group, while the lung uptake of ^99mTc-NAG-PEI was significantly higher in the ZYM treatment group compared to that in the control group. These results demonstrate that NAG-PEI is a potent MicroSPECT imaging-guided theranostic platform for IPF diagnosis and therapy.

Andrographolide alleviates bleomycin-induced NLRP3 inflammasome activation and epithelial-mesenchymal transition in lung epithelial cells by suppressing AKT/mTOR signaling pathway

Background

Andrographolide (Andro), a diterpenoid extracted from Andrographis paniculata, has been shown to attenuate pulmonary fibrosis in rodents; however, the potential mechanisms remain largely unclear. This study investigated whether and how Andro alleviates bleomycin (BLM)-induced NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activation and epithelial-mesenchymal transition (EMT) in the lung epithelial cells.

Methods

The in vivo effects of Andro were evaluated in a rat model of BLM-induced pulmonary fibrosis. The roles of Andro in BLM-induced NLRP3 inflammasome activation, EMT and AKT/mTOR signaling were investigated using human alveolar epithelial A549 cells.

Results

We found that Andro significantly alleviated pulmonary edema and histopathological changes, decreased weight loss, and reduced collagen deposition. Andro downregulated the levels of NLRP3, the adaptor molecule apoptosis-associated speck-like protein containing a CARD (ASC), and Caspase-1 in the lungs of BLM-treated rats, suggesting the inhibitory effect of Andro on NLRP3 inflammasome activation in vivo. Additionally, the symptoms of BLM-mediated EMT phenotype in the lung were also attenuated after Andro administration. In vitro, Andro also markedly inhibited BLM-induced NLRP3 inflammasome activation and EMT in A549 cells. Moreover, Andro inhibited BLM-induced phosphorylation of AKT and mTOR in A549 cells, suggesting that AKT/mTOR inactivation mediates Andro-induced effects on BLM-induced NLRP3 inflammasome activation and EMT.

Conclusions

These data indicate that Andro can reduce BLM-induced pulmonary fibrosis through suppressing NLRP3 inflammasome activation and EMT in lung epithelial cells via AKT/mTOR signaling pathway.

Pulmonary fibrosis: Therapeutic and mechanistic insights into the role of phytochemicals

Pulmonary fibrosis (PF) is the devastating consequence of various inflammatory diseases of the lung. PF leads to a reduction of lung function, respiratory failure, and death. Several molecular pathways are involved in PF, such as inflammatory cytokines including tumor necrosis factor α (TNFα), tumor necrosis factor β1 (TNFβ1), interleukin 6 (IL-6), and interleukin 4 (IL-4), reactive oxygen species, matrix metalloproteases, and transforming growth factor-beta (TGF-β). Targeting these processes involved in the progression of PF is essential for the treatment of this disease. Natural products, including plant extracts and active compound that directly target the processes involved in PF, could be suitable therapeutic options with less adverse effects. In the present study, we reviewed the protective effects and the therapeutic role of various bioactive compounds from plants in PF management.

CREB-dependent LPA-induced signaling initiates a pro-fibrotic feedback loop between small airway basal cells and fibroblasts

Background

Lysophosphatidic acid (LPA), generated extracellularly by the action of autotaxin and phospholipase A2, functions through LPA receptors (LPARs) or sphingosine-1-phosphate receptors (S1PRs) to induce pro-fibrotic signaling in the lower respiratory tract of patients with idiopathic pulmonary fibrosis (IPF). We hypothesized that LPA induces changes in small airway epithelial (SAE) basal cells (BC) that create cross-talk between the BC and normal human lung fibroblasts (NHLF), enhancing myofibroblast formation.

Methods

To assess LPA-induced signaling, BC were treated with LPA for 2.5 min and cell lysates were analyzed by phosphokinase array and Western blot. To assess transcriptional changes, BC were treated with LPA for 3 h and harvested for collection and analysis of RNA by quantitative polymerase chain reaction (qPCR). To assess signaling protein production and function, BC were washed thoroughly after LPA treatment and incubated for 24 h before collection for protein analysis by ELISA or functional analysis by transfer of conditioned medium to NHLF cultures. Transcription, protein production, and proliferation of NHLF were assessed.

Results

LPA treatment induced signaling by cAMP response element-binding protein (CREB), extracellular signal-related kinases 1 and 2 (Erk1/2), and epithelial growth factor receptor (EGFR) resulting in elevated expression of connective tissue growth factor (CTGF), endothelin-1 (EDN1/ET-1 protein), and platelet derived growth factor B (PDGFB) at the mRNA and protein levels. The conditioned medium from LPA-treated BC induced NHLF proliferation and increased NHLF expression of collagen I (COL1A1), smooth muscle actin (ACTA2), and autotaxin (ENPP2) at the mRNA and protein levels. Increased autotaxin secretion from NHLF correlated with increased LPA in the NHLF culture medium. Inhibition of CREB signaling blocked LPA-induced changes in BC transcription and translation as well as the pro-fibrotic effects of the conditioned medium on NHLF.

Conclusion

Inhibition of CREB signaling may represent a novel target for alleviating the LPA-induced pro-fibrotic feedback loop between SAE BC and NHLF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01677-0.

Changing Expression Profiles of Messenger RNA, MicroRNA, Long Non-coding RNA, and Circular RNA Reveal the Key Regulators and Interaction Networks of Competing Endogenous RNA in Pulmonary Fibrosis

Pulmonary fibrosis is a kind of interstitial lung disease with architectural remodeling of tissues and excessive matrix deposition. Apart from messenger RNA (mRNA), microRNA (miRNA), long non-coding RNA (lncRNA), and circular RNA (circRNA) could also play important roles in the regulatory processes of occurrence and progression of pulmonary fibrosis. In the present study, the pulmonary fibrosis model was administered with bleomycin. Whole transcriptome sequencing analysis was applied to investigate the expression profiles of mRNAs, lncRNAs, circRNAs, and miRNAs. After comparing bleomycin-induced pulmonary fibrosis model lung samples and controls, 286 lncRNAs, 192 mRNAs, 605 circRNAs, and 32 miRNAs were found to be differentially expressed. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to investigate the potential functions of these differentially expressed (DE) mRNAs and non-coding RNAs (ncRNAs). The terms related to inflammatory response and tumor necrosis factor (TNF) signaling pathway were enriched, implying potential roles in regulatory process. In addition, two co-expression networks were also constructed to understand the internal regulating relationships of these mRNAs and ncRNAs. Our study provides a systematic perspective on the potential functions of these DE mRNAs and ncRNAs during PF process and could help pave the way for effective therapeutics for this devastating and complex disease.

Kathon Induces Fibrotic Inflammation in Lungs: The First Animal Study Revealing a Causal Relationship between Humidifier Disinfectant Exposure and Eosinophil and Th2-Mediated Fibrosis Induction

Currently available toxicity data on humidifier disinfectants are primarily limited to polyhexamethylene guanidine phosphate-induced lung fibrosis. We, therefore, investigated whether the sterilizer component Kathon, which is a mixture of chloromethylisothiazolinone and methylisothiazolinone, induces fibrotic lung injury following direct lung exposure in an animal model. Mice were intratracheally instilled with either the vehicle or Kathon. Differential cell counts, cytokine analysis, and histological analysis of lung tissue were then performed to characterize the injury features, and we investigated whether Kathon altered fibrosis-related gene expression in lung tissues via RNA-Seq and bioinformatics. Cell counting showed that Kathon exposure increased the proportion of macrophages, eosinophils, and neutrophils. Moreover, T helper 2 (Th2) cytokine levels in the bronchoalveolar lavage were significantly increased in the Kathon groups. Histopathological analysis revealed increased perivascular/alveolar inflammation, eosinophilic cells, mucous cell hyperplasia, and pulmonary fibrosis following Kathon exposure. Additionally, Kathon exposure modulated the expression of genes related to fibrotic inflammation, including the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway, extracellular signal regulated kinase (ERK)1 and ERK2 cascade, extracellular matrix (ECM)-receptor interaction pathway, transforming growth factor beta receptor signaling pathway, cellular response to tumor necrosis factor, and collagen fibril organization. Our results suggest that Kathon exposure is associated with fibrotic lung injury via a Th2-dependent pathway and is thus a possible risk factor for fibrosis.

Inhibition of the SET8 Pathway Ameliorates Lung Fibrosis Even Through Fibroblast Dedifferentiation

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease of unknown etiopathogenesis. The activation of extracellular matrix (ECM)-producing myofibroblasts plays a key role in fibrotic tissue remodeling. The dedifferentiation of myofibroblasts has attracted considerable attention as a promising target for the development of effective therapeutic interventions against IPF. Here, we screened a small library of epigenetics-related inhibitors using dedifferentiation assay of lung myofibroblasts prepared from a patient at the terminal stages of IPF and chose UNC0379. The inhibition of SET8, a histone H4 lysine 20 (H4K20) monomethyltransferase, by UNC0379 markedly suppressed the expression of α-smooth muscle actin (SMA) and ED-A-fibronectin in myofibroblasts. In IPF myofibroblasts, SET8 expression and H4K20 monomethylation (H4K20me1) levels, which were significantly higher than those in normal human lung fibroblasts, were reduced upon treatment with UNC0379. Hence, the changes in the expression of the two fibrotic markers clearly correlated with those in SET8 expression and H4K20me1 level. Furthermore, in a mouse model of bleomycin (BLM)-induced lung fibrosis, the intratracheal administration of UNC0379 at an early fibrotic stage markedly ameliorated the histopathological changes associated with collagen deposition in the lungs. However, treatment with UNC0379 did not significantly affect the number of proinflammatory cells or cytokine production in the bronchoalveolar lavage fluids from mice treated with BLM. In the BLM-injured lung, SET8 was predominantly localized to the nuclei of α-SMA-positive cells, which colocalized with H4K20me1. Taken together, our results indicate that the inhibition of SET8 resulting in myofibroblast dedifferentiation may partly mitigate lung fibrosis without affecting the inflammatory responses.

Andrographolide attenuates epithelial-mesenchymal transition induced by TGF-β1 in alveolar epithelial cells

Andrographolide (Andro), a component from Chinese medicinal herb Andrographis paniculata, could alleviate pulmonary fibrosis in rodents. Yet, whether and how Andro mitigates epithelial-mesenchymal transition (EMT) induced by TGF-β1 remain unknown. This study aimed to explore the effect of Andro on TGF-β1-induced EMT in human alveolar epithelial cells (AECs) and the mechanisms involved. We illustrated that Andro inhibited TGF-β1-induced EMT and EMT-related transcription factors in alveolar epithelial A549 cells. Andro also reduced TGF-β1-induced cell migration and synthesis of pro-fibrotic factors (ie CCN-2, TGF-β1), matrix metalloproteinases (ie MMP-2, MMP-9) and extracellular matrix (ECM) components (ie collagen 1), implying the inhibiting effect of Andro on TGF-β1-induced EMT-like cell behaviours. Mechanistically, Andro treatment not only repressed TGF-β1-induced Smad2/3 phosphorylation and Smad4 nuclear translocation, but also suppressed TGF-β1-induced Erk1/2 phosphorylation and nuclear translocation in A549 cells. And treatment with ALK5 inhibitor (SB431542) or Erk1/2 inhibitors (SCH772984 and PD98059) remarkably reduced EMT evoked by TGF-β1. In addition, Andro also reduced TGF-β1-induced intracellular ROS generation and NOX4 expression, and elevated antioxidant superoxide dismutase 2 (SOD2) expression, demonstrating the inhibiting effect of Andro on TGF-β1-induced oxidative stress, which is closely linked to EMT. Furthermore, Andro remarkably attenuated TGF-β1-induced down-regulation of sirtuin1 (Sirt1) and forkhead box O3 (FOXO3), implying that Andro protects AECs from EMT partially by activating Sirt1/FOXO3-mediated anti-oxidative stress pathway. In conclusion, Andro represses TGF-β1-induced EMT in AECs by suppressing Smad2/3 and Erk1/2 signalling pathways and is also closely linked to the activation of sirt1/FOXO3-mediated anti-oxidative stress pathway.

Revisiting Cell Death Responses in Fibrotic Lung Disease: Crosstalk between Structured and Non-Structured Cells

Fibrosis is a life-threatening disorder caused by excessive formation of connective tissue that can affect several critical organs. Innate immune cells are involved in the development of various disorders, including lung fibrosis. To date, several hematopoietic cell types have been implicated in fibrosis, including pro-fibrotic monocytes like fibrocytes and segregated-nucleus-containing atypical monocytes (SatMs), but the precise cellular and molecular mechanisms underlying its development remain unclear. Repetitive injury and subsequent cell death response are triggering events for lung fibrosis development. Crosstalk between lung structured and non-structured cells is known to regulate the key molecular event. We recently reported that RNA-binding motif protein 7 (RBM7) expression is highly upregulated in the fibrotic lung and plays fundamental roles in fibrosis development. RBM7 regulates nuclear degradation of NEAT1 non-coding RNA, resulting in sustained apoptosis in the lung epithelium and fibrosis. Apoptotic epithelial cells produce CXCL12, which leads to the recruitment of pro-fibrotic monocytes. Apoptosis is also the main source of autoantigens. Recent studies have revealed important functions for natural autoantibodies that react with specific sets of self-antigens and are unique to individual diseases. Here, we review recent insights into lung fibrosis development in association with crosstalk between structured cells like lung epithelial cells and non-structured cells like migrating immune cells, and discuss their relevance to acquired immunity through natural autoantibody production.

Middle East Respiratory Syndrome-Coronavirus Infection into Established hDPP4-Transgenic Mice Accelerates Lung Damage Via Activation of the Pro-Inflammatory Response and Pulmonary Fibrosis

Middle East respiratory syndrome coronavirus (MERS-CoV) infects the lower respiratory airway of humans, leading to severe acute respiratory failure. Unlike human dipeptidyl peptidase 4 (hDPP4), a receptor for MERS-CoV, mouse DPP4 (mDPP4) failed to support MERS-CoV infection. Consequently, diverse transgenic mouse models expressing hDPP4 have been developed using diverse methods, although some models show no mortality and/or only transient and mild-to-moderate clinical signs following MERS-CoV infection. Additionally, overexpressed hDPP4 is associated with neurological complications and breeding difficulties in some transgenic mice, resulting in impeding further studies. Here, we generated stable hDPP4-transgenic mice that were sufficiently susceptible to MERS-CoV infection. The transgenic mice showed weight loss, decreased pulmonary function, and increased mortality with minimal perturbation of overexpressed hDPP4 after MERS-CoV infection. In addition, we observed histopathological signs indicative of progressive pulmonary fibrosis, including thickened alveolar septa, infiltration of inflammatory monocytes, and macrophage polarization as well as elevated expression of profibrotic molecules and acute inflammatory response in the lung of MERS-CoV-infected hDPP4-transgenic mice. Collectively, we suggest that this hDPP4-transgenic mouse is useful in understanding the pathogenesis of MERS-CoV infection and for antiviral research and vaccine development against the virus.

New therapeutic strategies for IPF: Based on the "phagocytosis-secretion-immunization" network regulation mechanism of pulmonary macrophages

Pulmonary fibrosis is a chronic and progressive interstitial lung disease of known and unknown etiology. Over the past decades, macrophages have been recognized to play a significant role in IPF pathogenesis. According to their anatomical loci, macrophages can be divided to alveolar macrophages (AMs) subtypes and interstitial macrophages subtypes (IMs) with different responsibility in the damage defense response. Depending on diverse chemokines and cytokines in local microenvironments, macrophages can be induced and polarized to either classically activated (M1) or alternatively activated (M2) phenotypes in different stages of immunity. Therefore, we hypothesize that there is a "phagocytosis-secretion-immunization" network regulation of pulmonary macrophages related to a number of chemokines and cytokines. In this paper, we summarize and discuss the role of chemokines and cytokines involved in the "phagocytosis-secretion-immunization" network regulation mechanism of pulmonary macrophages, pointing toward novel therapeutic approaches based on the network target regulation in the field. Therapeutic strategies focused on modifying the chemokines, cytokines and the network are promising for the pharmacotherapy of IPF. Some Traditional Chinese medicines may have more superiorities in delaying the progression of pulmonary fibrosis for their multi-target activities of this network regulation.

Angiotensin-(1-7) Attenuated Cigarette Smoking-related Pulmonary Fibrosis via Improving the Impaired Autophagy Caused by Nicotinamide Adenine Dinucleotide Phosphate Reduced Oxidase 4-Dependent Reactive Oxygen Species

Cigarette smoking is acknowledged as the major risk factor of pulmonary fibrosis. Angiotensin (Ang) II has been reported to aggravate smoking-induced lung fibrosis, whereas the effect of Ang-(1-7) on smoking-related lung fibrosis remains unknown. The autophagy, being activated by reactive oxygen species (ROS), is identified as a novel mechanism of pulmonary fibrosis. However, whether autophagy is involved in regulation of smoking-induced lung fibrosis still needs investigation. Here, we aim to investigate the effect of Ang-(1-7) on smoking-related lung fibrosis by the regulation of autophagy and ROS. In vivo, Ang-(1-7) was constantly infused into passive smoking rats for 8 weeks. In vitro, primary lung fibroblasts were pretreated with antioxidant, nicotinamide adenine dinucleotide phosphate reduced oxidase (NOX) 4 siRNA, or light chain (LC) 3B siRNA before exposure to cigarette smoke extract (CSE). GFP-mCherry red fluorescent protein-LC3 advenovirus was introduced to evaluate the autophagic flux in cells. We found that Ang-(1-7) reduced hydrogen peroxide (H₂O₂) concentration, protein levels of NOX4, and autophagy impairment, as well as improving lung fibrosis induced by smoking stimulation in vivo. In vitro, CSE treatment elevated NOX4 protein expression and ROS production, resulting in the accumulation of impaired autophagosomes in fibroblasts. LC3B depletion enhanced CSE-induced collagen synthesis. Treatment with antioxidants or NOX4 siRNA inhibited CSE-induced insufficient autophagic flux and collagen production. In contrast, the action of Ang-(1-7) opposed the effects of CSE. In conclusion, Ang-(1-7) improves smoking-induced pulmonary fibrosis via attenuating the impaired autophagy caused by NOX4-dependent ROS in vivo and in vitro.

Local activation of the pulmonary extravascular angiotensin system induces epithelial apoptosis and lung fibrosis

Previous work suggests that a local extravascular angiotensin system plays an important role in the development of pulmonary fibrosis through stimulation of alveolar epithelial cell (AEC) apoptosis and collagen deposition. To demonstrate a causative role for the local tissue angiotensin (ANG) system in lung fibrosis, we hypothesize that overexpression of the angiotensinogen (AGT) gene or pharmacologic elevation of lung tissue ANG II levels might cause apoptosis of AECs and lung fibrosis. ANGII levels were elevated in rat or mouse lung tissue by intratracheal instillation of either purified ANGII or an adenovirus expressing AGT, or by ubiquitous overexpression of AGT in transgenic mice. Intratracheal instillation of purified ANGII caused significant collagen accumulation in lung tissue, both ex vivo and in vivo. Ubiquitous overexpression of AGT enhanced the profibrotic effect of bleomycin given at suboptimal doses. Intratracheal delivery of an adenoviral vector expressing mouse AGT (Ad-AGT) overexpressed AGT primarily in AECs and caused both apoptosis of AECs and pulmonary fibrosis. The lung collagen accumulation and AEC apoptosis caused by Ad-AGT was blocked by the caspase inhibitor ZVAD-fmk, by the ANG receptor AT1 antagonist Losartan or by the non-selective ANGII receptor antagonist Saralasin. Together, these data support the hypothesis that elevated pulmonary expression of AGT and its conversion to angiotensin II plays a causative role in the development of lung fibrosis through its induction of AEC apoptosis.

The Expression of AQP1 IS Modified in Lung of Patients With Idiopathic Pulmonary Fibrosis: Addressing a Possible New Target

Activation of the epithelial-mesenchymal transition process (EMT) by which alveolar cells in human lung tissue undergo differentiation giving rise to a mesenchymal phenotype (fibroblast/miofibroblasts) has been well recognized as a key element in the origin of idiopathic pulmonary fibrosis (IPF). Here we analyzed expression of AQP1 in lung biopsies of patients diagnosed with IPF, and compared it to biopsies derived from patients with diverse lung pneumonies, such as hypersensitivity pneumonitis, sarcoidosis or normal lungs. Immunostaining for AQP1 showed a clear increment of AQP1 localized in the alveolar epithelium in biopsies from IPF patients alone. Moreover, to examine the possible participation of AQP1 in the pathophysiology of IPF, we evaluated its role in the pro-fibrotic transformation induced by transforming growth factor (TGF-β) in vitro. Human alveolar epithelial cells (A549), and fibroblasts derived from an IPF patient (LL29), or fibroblasts from healthy normal lung tissue (MRC-5), were treated with TGF-β, and levels of expression of AQP1, as well as those of E-cadherin, vimentin, α-SMA and collagen were analyzed by RT-qPCR, western blot and immunohistochemistry. An increase of AQP1 mRNA and protein after TGF-β treatment (4–72h) was observed either in A549 or IPF fibroblast-LL29 but not in MRC-5 fibroblasts. A gradual reduction of E-cadherin, and increased expression of vimentin, with no changes in α-SMA levels were observed in A549. Whereas in LL29 and MRC-5, TGF-β1 elicited a large production of collagen and α-SMA that was significantly greater in IPF fibroblast-LL29. Changes observed are consistent with activation of EMT by TGF-β, but whether modifications in AQP1 expression are responsible or independent events occurring at the same time is still unknown. Our results suggest that AQP1 plays a role in the pro-fibrotic TGF-β action and contributes to the etiology and pathophysiology of IPF. Understanding AQP1's role will help us comprehend the fate of this disease.

Identification of novel inhibitors of DDR1 against idiopathic pulmonary fibrosis by integrative transcriptome meta-analysis, computational and experimental screening

Idiopathic pulmonary fibrosis (IPF) is a kind of a chronic and fatal lung disease leading to progressive lung function decline. Although several RNA microarray studies on IPF patients have been reported, their results were merely specific to each study with distinct platforms or sample types. In the current study, an integrative transcriptome meta-analysis of IPF was performed to explore regulated pathways, based on four independent expression profiling microarrays of IPF datasets, including 73 samples from IPF tissues or lung fibroblast cells. The results suggested the discoidin domain receptor 1 (DDR1) and downstream c-Jun N-terminal kinases (JNK) pathway may play important roles in the progression of IPF. To our knowledge, discoidin domain receptor 1 (DDR1) is a kind of receptor tyrosine kinase (RTK) with a unique ability to bind both fibrillar and non-fibrillar collagens. Based on the crystallographic structures of DDR1, the combination of molecular dynamics simulation and a hybrid protocol of a virtual screening method, comprised of PBVS (multicomplex-pharmacophore based virtual screening) and DBVS (docking based virtual screening) methods were used for retrieving novel DDR1 inhibitors from the SPECS database. Twelve hit compounds were selected from the hit compounds and shifted to experimental validations, and the most potent compound was evaluated for its anti-IPF capacity on murine IPF models. Thus, these results may provide valuable information for further discovery of potential lead compounds for IPF therapy.

Mouse Lung Fibroblast Resistance to Fas-Mediated Apoptosis Is Dependent on the Baculoviral Inhibitor of Apoptosis Protein 4 and the Cellular FLICE-Inhibitory Protein

A characteristic feature of idiopathic pulmonary fibrosis (IPF) is accumulation of apoptotic resistant fibroblasts/myofibroblasts in the fibroblastic foci. As caveolin (Cav)-null mice develop pulmonary fibrosis (PF), we hypothesized that the participating fibroblasts display an apoptosis-resistant phenotype. To test this hypothesis and identify the molecular mechanisms involved we isolated lung fibroblasts from Cav-null mice and examined the expression of several inhibitors of apoptosis (IAPs), of c-FLIP, of Bcl-2 proteins and of the death receptor CD95/Fas. We found significant increase in XIAP and c-FLIP constitutive protein expression with no alteration of Bcl-2 and lower levels of CD95/Fas. The isolated fibroblasts were then treated with the CD95/Fas ligand (FasL) to induce apoptosis. While the morphological and biochemical alterations induced by FasL were similar in wild-type (wt) and Cav-null mouse lung fibroblasts, the time course and the extent of the alterations were greater in the Cav-null fibroblasts. Several salient features of Cav-null fibroblasts response such as loss of membrane potential, fragmentation of the mitochondrial continuum concurrent with caspase-8 activation, and subsequent Bid cleavage, prior to caspase-3 activation were detected. Furthermore, M30 antigen formation, phosphatidylserine expression and DNA fragmentation were caspase-3 dependent. SiRNA-mediated silencing of XIAP and c-FLIP, individually or combined, enhanced the sensitivity of lung fibroblasts to FasL-induced apoptosis. Pharmacological inhibition of Bcl-2 had no effect. Together our findings support a mechanism in which CD95/Fas engagement activates caspase-8, inducing mitochondrial apoptosis through Bid cleavage. XIAP and c-FLIP fine tune this process in a cell-type specific manner.

Epigenetic Regulation of Interleukin 6 by Histone Acetylation in Macrophages and Its Role in Paraquat-Induced Pulmonary Fibrosis

Overexpression of interleukin 6 (IL-6) has been proposed to contribute to pulmonary fibrosis and other fibrotic diseases. However, the regulatory mechanisms and the role of IL-6 in fibrosis remain poorly understood. Epigenetics refers to alterations of gene expression without changes in the DNA sequence. Alternation of chromatin accessibility by histone acetylation acts as a critical epigenetic mechanism to regulate various gene transcriptions. The goal of this study was to determine the impact of IL-6 in paraquat (PQ)-induced pulmonary fibrosis and to explore whether the epigenetic regulations may play a role in transcriptional regulation of IL-6. In PQ-treated lungs and macrophages, we found that the mRNA and protein expression of IL-6 was robustly increased in a time-dependent and a dose-dependent manner. Our data demonstrated that PQ-induced IL-6 expression in macrophages plays a central role in pulmonary fibrosis through enhanced epithelial-to-mesenchymal transition (EMT). IL-6 expression and its role to enhance PQ-induced pulmonary fibrosis were increased by histone deacetylase (HDAC) inhibition and prevented by histone acetyltransferase (HAT) inhibition. In addition, the ability of CRISPR-ON transcription activation system (CRISPR-ON) to promote transcription of IL-6 was enhanced by HDAC inhibitor and blocked by HAT inhibitor. Chromatin immunoprecipitation experiments revealed that HDAC inhibitor increased histones activation marks H3K4me3 and H3K9ac at IL-6 promoter regions. In conclusion, IL-6 functioning through EMT in PQ-induced pulmonary fibrosis was regulated dynamically by HDAC and HAT both in vitro and in vivo via epigenetically regulating chromatin accessibility.

Quantitative assessment of lung stiffness in patients with interstitial lung disease using MR elastography

PURPOSE

To investigate the use of magnetic resonance elastography (MRE) in the quantitative assessment of pulmonary fibrosis by comparing quantitative shear stiffness measurements of lung parenchyma in patients diagnosed with fibrotic interstitial lung disease (ILD) and healthy controls.

MATERIALS AND METHODS

A 1.5T spin-echo, echo planar imaging MRE (SE-EPI MRE) pulse sequence was utilized to assess absolute lung shear stiffness in 15 patients with diagnosed ILD and in 11 healthy controls. Data were collected at residual volume (RV) and total lung capacity (TLC). Spirometry data were obtained immediately prior to scanning. To test for statistical significance between RV and TLC shear stiffness estimates a two-sample t-test was performed. To assess variability within individual subject shear stiffness estimates, the intraclass correlation coefficient (ICC) and Krippendorff's alpha were calculated.

RESULTS

Patients with ILD exhibited an average (±1 standard deviation) shear stiffness of 2.74 (±0.896) kPa at TLC and 1.32 (±0.300) kPa at RV. The corresponding values for healthy individuals were 1.33 (±0.195) kPa and 0.849 (±0.250) kPa, respectively. The difference in shear stiffness between RV and TLC was statistically significant (P < 0.001). At TLC, the ICC and alpha values were 0.909 and 0.887, respectively. At RV, the ICC and alpha values were 0.852 and 0.862, respectively.

CONCLUSION

In subjects with known fibrotic interstitial lung disease, parenchymal shear stiffness is increased when compared to normal controls at both RV and TLC, with TLC demonstrating the most significant difference. MRE-derived parenchymal shear stiffness is a promising new noninvasive imaging-based biomarker of interstitial lung disease.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:365-374.

Prostaglandin D2 Attenuates Bleomycin-Induced Lung Inflammation and Pulmonary Fibrosis

Pulmonary fibrosis is a progressive and fatal lung disease with limited therapeutic options. Although it is well known that lipid mediator prostaglandins are involved in the development of pulmonary fibrosis, the role of prostaglandin D₂ (PGD₂) remains unknown. Here, we investigated whether genetic disruption of hematopoietic PGD synthase (H-PGDS) affects the bleomycin-induced lung inflammation and pulmonary fibrosis in mouse. Compared with H-PGDS naïve (WT) mice, H-PGDS-deficient mice (H-PGDS^-/-) represented increased collagen deposition in lungs 14 days after the bleomycin injection. The enhanced fibrotic response was accompanied by an increased mRNA expression of inflammatory mediators, including tumor necrosis factor-α, monocyte chemoattractant protein-1, and cyclooxygenase-2 on day 3. H-PGDS deficiency also increased vascular permeability on day 3 and infiltration of neutrophils and macrophages in lungs on day 3 and 7. Immunostaining showed that the neutrophils and macrophages expressed H-PGDS, and its mRNA expression was increased on day 3and 7 in WT lungs. These observations suggest that H-PGDS-derived PGD₂ plays a protective role in bleomycin-induced lung inflammation and pulmonary fibrosis.

Emodin ameliorates bleomycin-induced pulmonary fibrosis in rats by suppressing epithelial-mesenchymal transition and fibroblast activation

Aberrant activation of TGF-β1 is frequently encountered and promotes epithelial-mesenchymal transition (EMT) and fibroblast activation in pulmonary fibrosis. The present study investigated whether emodin mediates its effect via suppressing TGF-β1-induced EMT and fibroblast activation in bleomycin (BLM)-induced pulmonary fibrosis in rats. Here, we found that emodin induced apoptosis and inhibited cellular proliferation, migration and differentiation in TGF-β1-stimulated human embryonic lung fibroblasts (HELFs). Emodin suppressed TGF-β1-induced EMT in a dose- and time-dependent manner in alveolar epithelial A549 cells. Emodin also inhibited TGF-β1-induced Smad2, Smad3 and Erk1/2 activation, suggesting that Smad2/3 and Erk1/2 inactivation mediated the emodin-induced effects on TGF-β1-induced EMT. Additionally, we provided in vivo evidence suggesting that emodin apparently alleviated BLM-induced pulmonary fibrosis and improved pulmonary function by inhibiting TGF-β1 signaling and subsequently repressing EMT, fibroblast activation and extracellular matrix (ECM) deposition. Taken together, our data suggest that emodin mediates its effects mainly via inhibition of EMT and fibroblast activation and thus has a potential for the treatment of pulmonary fibrosis.

Interstitial Lung Disease in West Highland White Terriers

Progressive respiratory failure and pulmonary fibrosis in West Highland White Terriers (WHWT) is an apparently genetic disorder of unknown pathogenesis. This study characterizes the light microscopic, ultrastructural, and immunohistochemical features of affected WHWT in comparison with lesions in usual interstitial pneumonia (UIP) of humans. Lesions in WHWT were confined to the expansion of the interstitial space of alveolar septa by extracellular matrix (ECM) determined to be mixtures of type-I and -III collagens. Features of UIP such as intra-alveolar fibroblastic foci, subpleural distribution, and honeycombing were not observed in six WHWT. Comparison with normal dogs showed no apparent increase in septal myofibroblasts. Ultrastructually, the ECM in alveolar septa consisted of large aggregates of periodic collagen filaments underlying alveolar capillaries that were surrounded by thick bands of amorphous to fine fibrillar matrix. This study suggests that chronic pulmonary disease of WHWT is a result of aberrant collagen regulation.

Ultrasound in the interstitial pulmonary fibrosis. Can it facilitate a best routine assessment in rheumatic disorders?

Ultrasound (US) is increasing its potential in the assessment of several rheumatic disorders. Recently, different applications of this imaging technique have emerged. Interesting data supporting its utility and validity in the assessment of the lung to detect and quantify interstitial pulmonary fibrosis in rheumatic diseases, even in subclinical phases, have been reported. The main purpose of this review is to provide an overview of the role of US in the assessment of interstitial pulmonary fibrosis in rheumatic disorders and to discuss the current evidence supporting its clinical relevance in daily clinical practice.

The Aldo-Keto Reductase AKR1B10 Is Up-Regulated in Keloid Epidermis, Implicating Retinoic Acid Pathway Dysregulation in the Pathogenesis of Keloid Disease

Keloid disease is a recurrent fibroproliferative cutaneous tumor of unknown pathogenesis for which clinical management remains unsatisfactory. To obtain new insights into hitherto underappreciated aspects of keloid pathobiology, we took a laser capture microdissection-based, whole-genome microarray analysis approach to identify distinct keloid disease-associated gene expression patterns within defined keloid regions. Identification of the aldo-keto reductase enzyme AKR1B10 as highly up-regulated in keloid epidermis suggested that an imbalance of retinoic acid metabolism is likely associated with keloid disease. Here, we show that AKR1B10 transfection into normal human keratinocytes reproduced the abnormal retinoic acid pathway expression pattern we had identified in keloid epidermis. Cotransfection of AKR1B10 with a luciferase reporter plasmid showed reduced retinoic acid response element activity, supporting the hypothesis of retinoic acid synthesis deficiency in keloid epidermis. Paracrine signals released by AKR1B10-overexpressing keratinocytes into conditioned medium resulted in up-regulation of transforming growth factor-β1, transforming growth factor-β2, and collagens I and III in both keloid and normal skin fibroblasts, mimicking the typical profibrotic keloid profile. Our study results suggest that insufficient retinoic acid synthesis by keloid epidermal keratinocytes may contribute to the pathogenesis of keloid disease. We refocus attention on the role of injured epithelium in keloid disease and identify AKR1B10 as a potential new target in future management of keloid disease.

Staphylococcus aureus induces TGF-β1 and bFGF expression through the activation of AP-1 and NF-κB transcription factors in bovine mammary gland fibroblasts

Staphylococcus aureus is a common Gram-positive pathogen that causes bovine mastitis, a persistent infection of the bovine mammary gland. To better understand the importance of bovine mammary fibroblasts (BMFBs) and the roles of the TLR-NF-κB and TLR-AP-1 signaling pathways in the regulation of S. aureus-associated mastitis and mammary fibosis, BMFBs cultured in vitro were stimulated with different concentrations of heat-inactivated S. aureus to analyze the gene and protein expression of toll-like receptor 2 (TLR2), toll-like receptor 4 (TLR4), transforming growth factor beta 1 (TGF-β1), basic fibroblast growth factor (bFGF) as well as the protein expression of nuclear factor-kappa B (NF-κB) and activation protein-1 (AP-1) by means of quantitative polymerase chain reaction (qPCR) and western blotting, respectively. Specific NF-κB and AP-1 inhibitors were also used to investigate their effects on the regulation of TGF-β1 and bFGF expression. The results indicated that, in addition to increasing mRNA and protein expression of TLR2 and TLR4, S. aureus could also upregulate TGF-β1 and bFGF mRNA expression and secretion through the activation of NF-κB and AP-1. The increase in TGF-β1 and bFGF expression was shown to be inhibited by AP-1- and NF-κB-specific inhibitors. Taken together, S. aureus induces TGF-β1 and bFGF expression through the activation of AP-1 and NF-κB in BMFBs. This information offers new potential targets for the treatment of bovine mammary fibrosis.

Establishment of a mouse model for pulmonary inflammation and fibrosis by intratracheal instillation of polyhexamethyleneguanidine phosphate

Although several animal models have been developed to study human pulmonary fibrosis, lack of a perfect model has raised the need for various animal models of pulmonary fibrosis. In this study, we evaluated the pulmonary effect of polyhexamethyleneguanidine phosphate instillation into the lungs of mice to determine the potential of these mice as a murine model of pulmonary fibrosis. Intratracheal instillation of polyhexamethyleneguanidine phosphate induced severe lung inflammation manifested by the infiltration of mononuclear cells and neutrophils and increased production of IL-6, TNF-α, CCL2 and CXCL1. The lung inflammation gradually increased until 28 days after polyhexamethyleneguanidine phosphate exposure, and increases of collagen deposition and TGF-β production, which are indicators of pulmonary fibrosis, were seen. Our study showed that intratracheal instillation of polyhexamethyleneguanidine phosphate induces pulmonary inflammation and fibrosis in mice.

Plakoglobin expression in fibroblasts and its role in idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is an interstitial fibrotic lung disease of unknown origin and without effective therapy characterized by deposition of extracellular matrix by activated fibroblasts in the lung. Fibroblast activation in IPF is associated with Wnt/β-catenin signaling, but little is known about the role of the β-catenin-homologous desmosomal protein, plakoglobin (PG), in IPF. The objective of this study was to assess the functional role of PG in human lung fibroblasts in IPF.

Methods

Human lung fibroblasts from normal or IPF patients were transfected with siRNA targeting PG and used to assess cellular adhesion to a fibronectin substrate, apoptosis and proliferation. Statistical analysis was performed using Student’s t-test with Mann–Whitney post-hoc analyses and results were considered significant when p < 0.05.

Results

We found that IPF lung fibroblasts expressed less PG protein than control fibroblasts, but that characteristic fibroblast phenotypes (adhesion, proliferation, and apoptosis) were not controlled by PG expression. Consistent with this, normal fibroblasts in which PG was silenced displayed no change in functional phenotype.

Conclusions

We conclude that diminished PG levels in IPF lung fibroblasts do not directly affect certain phenotypic behaviors. Further study is needed to identify the functional consequences of decreased PG in these cells.

MicroRNAs as potential targets for progressive pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and devastating disorder. It is characterized by alveolar epithelial cell injury and activation, infiltration of inflammatory cells, initiation of epithelial mesenchymal transition (EMT), aberrant proliferation and activation of fibroblasts, exaggerated deposition of extracellular matrix (ECM) proteins, and finally leading to the destruction of lung parenchyma. MicroRNAs (miRNAs) are endogenous small non-coding RNA molecules that post-transcriptionally regulate gene expression in diverse biological and pathological processes, including cell proliferation, differentiation, apoptosis and metastasis. As a result, miRNAs have emerged as a major area of biomedical research with relevance to pulmonary fibrosis. In this context, the present review discusses specific patterns of dysregulated miRNAs in patients with IPF. Further, we discuss the current understanding of miRNAs involvement in regulating lung inflammation, TGF-β1-mediated EMT and fibroblast differentiation processes, ECM genes expression, and in the progression of lung fibrosis. The possible future directions that might lead to novel therapeutic strategies for the treatment of pulmonary fibrosis are also reviewed.

Different profiles of notch signaling in cigarette smoke-induced pulmonary emphysema and bleomycin-induced pulmonary fibrosis

OBJECTIVE

Different profiles of Notch signaling mediate naive T cell differentiation which might be involved in pulmonary emphysema and fibrosis.

METHODS

C57BL/6 mice were randomized into cigarette smoke (CS) exposure, bleomycin (BLM) exposure, and two separate groups of control for sham exposure to CS or BLM. The paratracheal lymph nodes of the animals were analyzed by real-time PCR and immunohistochemistry. Morphometry of the lung parenchyma, measurement of the cytokines, and cytometry of the bronchoalveolar lavage fluid (BALF) were also done accordingly.

RESULTS

In comparison with controls, all Notch receptors and ligands were upregulated by chronic CS exposure, especially Notch3 and DLL1 (P < 0.01), and this was in line with emphysema-like morphology and Th1-biased inflammation. While Notch3 and DLL1 were downregulated by BLM exposure (P < 0.01), those was in line with fibrotic lung remodeling and Th2 polarization.

CONCLUSIONS

This founding implies that the CS exposure but not the BLM exposure is capable of initiating Notch signaling in lymphoid tissue of the lung, which is likely relevant to the pathogenesis of pulmonary emphysema. Unable to initiate the Th1 response or inhibit it may lead to Th2 polarization and aberrant repair.

B cell activating factor is central to bleomycin- and IL-17-mediated experimental pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive devastating, yet untreatable fibrotic disease of unknown origin. We investigated the contribution of the B-cell activating factor (BAFF), a TNF family member recently implicated in the regulation of pathogenic IL-17-producing cells in autoimmune diseases. The contribution of BAFF was assessed in a murine model of lung fibrosis induced by airway administered bleomycin. We show that murine BAFF levels were strongly increased in the bronchoalveolar space and lungs after bleomycin exposure. We identified Gr1(+) neutrophils as an important source of BAFF upon BLM-induced lung inflammation and fibrosis. Genetic ablation of BAFF or BAFF neutralization by a soluble receptor significantly attenuated pulmonary fibrosis and IL-1β levels. We further demonstrate that bleomycin-induced BAFF expression and lung fibrosis were IL-1β and IL-17A dependent. BAFF was required for rIL-17A-induced lung fibrosis and augmented IL-17A production by CD3(+) T cells from murine fibrotic lungs ex vivo. Finally we report elevated levels of BAFF in bronchoalveolar lavages from IPF patients. Our data therefore support a role for BAFF in the establishment of pulmonary fibrosis and a crosstalk between IL-1β, BAFF and IL-17A.

The role of Bcl-2 family proteins in pulmonary fibrosis

Pulmonary fibrosis is characterized by epithelial injury, abnormal tissue repair, fibroproliferation and loss of pulmonary function as a result of a complex interaction of multiple cellular and molecular processes. There is accumulating evidence in support of a role for apoptosis in the pathogenesis of interstitial lung diseases. The Bcl-2 (B-cell lymphoma-2) family of proteins, which consists of antiapoptotic and pro-apoptotic members, is a critical regulator for apoptosis and development of pulmonary fibrosis. The association between Bcl-2 family members and various pathways and mediators has been also described in the pulmonary fibrosis. This article reviews the recent advances regarding the roles of Bcl-2 family as the apoptosis-regulatory factors in pulmonary fibrosis from human tissue studies, animal models, ex vivo and in vitro studies. Further understanding of apoptosis signaling regulation through Bcl-2 family proteins in the lung tissue may lead to better design of new therapeutic interventions for pulmonary fibrosis.

Future directions in idiopathic pulmonary fibrosis research. An NHLBI workshop report

The median survival of patients with idiopathic pulmonary fibrosis (IPF) continues to be approximately 3 years from the time of diagnosis, underscoring the lack of effective medical therapies for this disease. In the United States alone, approximately 40,000 patients die of this disease annually. In November 2012, the NHLBI held a workshop aimed at coordinating research efforts and accelerating the development of IPF therapies. Basic, translational, and clinical researchers gathered with representatives from the NHLBI, patient advocacy groups, pharmaceutical companies, and the U.S. Food and Drug Administration to review the current state of IPF research and identify priority areas, opportunities for collaborations, and directions for future research. The workshop was organized into groups that were tasked with assessing and making recommendations to promote progress in one of the following six critical areas of research: (1) biology of alveolar epithelial injury and aberrant repair; (2) role of extracellular matrix; (3) preclinical modeling; (4) role of inflammation and immunity; (5) genetic, epigenetic, and environmental determinants; (6) translation of discoveries into diagnostics and therapeutics. The workshop recommendations provide a basis for directing future research and strategic planning by scientific, professional, and patient communities and the NHLBI.

The transcription factor FOXM1 (Forkhead box M1): proliferation-specific expression, transcription factor function, target genes, mouse models, and normal biological roles

FOXM1 (Forkhead box M1) is a typical proliferation-associated transcription factor, which stimulates cell proliferation and exhibits a proliferation-specific expression pattern. Accordingly, both the expression and the transcriptional activity of FOXM1 are increased by proliferation signals, but decreased by antiproliferation signals, including the positive and negative regulation by protooncoproteins or tumor suppressors, respectively. FOXM1 stimulates cell cycle progression by promoting the entry into S-phase and M-phase. Moreover, FOXM1 is required for proper execution of mitosis. Accordingly, FOXM1 regulates the expression of genes, whose products control G1/S-transition, S-phase progression, G2/M-transition, and M-phase progression. Additionally, FOXM1 target genes encode proteins with functions in the execution of DNA replication and mitosis. FOXM1 is a transcriptional activator with a forkhead domain as DNA binding domain and with a very strong acidic transactivation domain. However, wild-type FOXM1 is (almost) inactive because the transactivation domain is repressed by three inhibitory domains. Inactive FOXM1 can be converted into a very potent transactivator by activating signals, which release the transactivation domain from its inhibition by the inhibitory domains. FOXM1 is essential for embryonic development and the foxm1 knockout is embryonically lethal. In adults, FOXM1 is important for tissue repair after injury. FOXM1 prevents premature senescence and interferes with contact inhibition. FOXM1 plays a role for maintenance of stem cell pluripotency and for self-renewal capacity of stem cells. The functions of FOXM1 in prevention of polyploidy and aneuploidy and in homologous recombination repair of DNA-double-strand breaks suggest an importance of FOXM1 for the maintenance of genomic stability and chromosomal integrity.

Experimental induction of pulmonary fibrosis in horses with the gammaherpesvirus equine herpesvirus 5

Gammaherpesviruses (γHV) are implicated in the pathogenesis of pulmonary fibrosis in humans and murine models of lung fibrosis, however there is little direct experimental evidence that such viruses induce lung fibrosis in the natural host. The equine γHV EHV 5 is associated with equine multinodular pulmonary fibrosis (EMPF), a progressive fibrosing lung disease in its natural host, the horse. Experimental reproduction of EMPF has not been attempted to date. We hypothesized that inoculation of EHV 5 isolated from cases of EMPF into the lungs of clinically normal horses would induce lung fibrosis similar to EMPF. Neutralizing antibody titers were measured in the horses before and after inoculation with EHV 5. PCR and virus isolation was used to detect EHV 5 in antemortem blood and BAL samples, and in tissues collected postmortem. Nodular pulmonary fibrosis and induction of myofibroblasts occurred in EHV 5 inoculated horses. Mean lung collagen in EHV 5 inoculated horses (80 µg/mg) was significantly increased compared to control horses (26 µg/mg) (p < 0.5), as was interstitial collagen (32.6% ± 1.2% vs 23% ± 1.4%) (mean ± SEM; p < 0.001). Virus was difficult to detect in infected horses throughout the experiment, although EHV 5 antigen was detected in the lung by immunohistochemistry. We conclude that the γHV EHV 5 can induce lung fibrosis in the horse, and hypothesize that induction of fibrosis occurs while the virus is latent within the lung. This is the first example of a γHV inducing lung fibrosis in the natural host.

Meta-analysis of genetic programs between idiopathic pulmonary fibrosis and sarcoidosis

Background

Idiopathic pulmonary fibrosis (IPF) and pulmonary sarcoidosis are typical interstitial lung diseases with unknown etiology that cause lethal lung damages. There are notable differences between these two pulmonary disorders, although they do share some similarities. Gene expression profiles have been reported independently, but differences on the transcriptional level between these two entities have not been investigated.

Methods/Results

All expression data of lung tissue samples for IPF and sarcoidosis were from published datasets in the Gene Expression Omnibus (GEO) repository. After cross platform normalization, the merged sample data were grouped together and were subjected to statistical analysis for finding discriminate genes. Gene enrichments with their corresponding functions were analyzed by the online analysis engine “Database for Annotation, Visualization and Integrated Discovery” (DAVID) 6.7, and genes interactions and functional networks were further analyzed by STRING 9.0 and Cytoscape 3.0.0 Beta1. One hundred and thirty signature genes could potentially differentiate one disease state from another. Compared with normal lung tissue, tissue affected by IPF and sarcoidosis displayed similar signatures that concentrated on proliferation and differentiation. Distinctly expressed genes that could distinguish IPF from sarcoidosis are more enriched in processes of cilium biogenesis or degradation and regulating T cell activations. Key discriminative network modules involve aspects of bone morphogenetic protein receptor two (BMPR2) related and v-myb myeloblastosis viral oncogene (MYB) related proliferation.

Conclusions

This study is the first attempt to examine the transcriptional regulation of IPF and sarcoidosis across different studies based on different working platforms. Groups of significant genes were found to clearly distinguish one condition from the other. While IPF and sarcoidosis share notable similarities in cell proliferation, differentiation and migration, remarkable differences between the diseases were found at the transcription level, suggesting that the two diseases are regulated by overlapping yet distinctive transcriptional networks.

Roles of p38 MAPK and JNK in TGF-β1-induced human alveolar epithelial to mesenchymal transition

BACKGROUND AND AIMS

Idiopathic pulmonary fibrosis (IPF) is associated with significant morbidity and mortality despite aggressive therapy. The aim of the present study is to investigate the roles of p38 MAPK and JNK in TGF-β1-induced human alveolar epithelial to mesenchymal transition (EMT), which could be a possible mechanism of IPF.

METHODS

A549 cells were treated with TGF-β1 (3 ng/mL) for 48 h to induce EMT. The expression of mesenchymal phenotypic markers including desmin, α-smooth muscle actin (α-SMA) and vimentin, and expression of epithelial phenotypic markers including E-cadherin, zonula occludens-1 (ZO-1) and aquaporin-5 (AQP5) were detected by Western blot. The roles of p38 MAPK and JNK in TGF-β1-mediated EMT were investigated using gene silencing and inhibitor SB-203580 and SP-600125.

RESULTS

The data showed that TGF-β1 induced A549 cells with an alveolar epithelial type II cell phenotype to undergo EMT. The process of EMT was accompanied by morphological alteration and expression of the myofibroblast marker desmin, α-SMA and vimentin, concomitant with a downregulation of the epithelial cell marker E-cadherin, ZO-1 and AQP5. TGF-β1-induced EMT occurred through phosphorylation of p38 MAPK and JNK and was inhibited by inhibitor SB-203580 and SP-600125 and gene silencing.

CONCLUSIONS

TGF-β1 induces A549 alveolar epithelial cells (AECs) to undergo EMT partially via p38 MAPK and JNK activation and supports the concept of EMT in lung epithelial cells.

LOX-mediated collagen crosslinking is responsible for fibrosis-enhanced metastasis

Tumor metastasis is a highly complex, dynamic, and inefficient process involving multiple steps, yet it accounts for more than 90% of cancer-related deaths. Although it has long been known that fibrotic signals enhance tumor progression and metastasis, the underlying molecular mechanisms are still unclear. Identifying events involved in creating environments that promote metastatic colonization and growth are critical for the development of effective cancer therapies. Here, we show a critical role for lysyl oxidase (LOX) in establishing a milieu within fibrosing tissues that is favorable to growth of metastastic tumor cells. We show that LOX-dependent collagen crosslinking is involved in creating a growth-permissive fibrotic microenvironment capable of supporting metastatic growth by enhancing tumor cell persistence and survival. We show that therapeutic targeting of LOX abrogates not only the extent to which fibrosis manifests, but also prevents fibrosis-enhanced metastatic colonization. Finally, we show that the LOX-mediated collagen crosslinking directly increases tumor cell proliferation, enhancing metastatic colonization and growth manifesting in vivo as increased metastasis. This is the first time that crosslinking of collagen I has been shown to enhance metastatic growth. These findings provide an important link between ECM homeostasis, fibrosis, and cancer with important clinical implications for both the treatment of fibrotic disease and cancer.

Thiol-redox antioxidants protect against lung vascular endothelial cytoskeletal alterations caused by pulmonary fibrosis inducer, bleomycin: comparison between classical thiol-protectant, N-acetyl-L-cysteine, and novel thiol antioxidant, N,N'-bis-2-mercaptoethyl isophthalamide

Lung vascular alterations and pulmonary hypertension associated with oxidative stress have been reported to be involved in idiopathic lung fibrosis (ILF). Therefore, here, we hypothesize that the widely used lung fibrosis inducer, bleomycin, would cause cytoskeletal rearrangement through thiol-redox alterations in the cultured lung vascular endothelial cell (EC) monolayers. We exposed the monolayers of primary bovine pulmonary artery ECs to bleomycin (10 µg) and studied the cytotoxicity, cytoskeletal rearrangements, and the macromolecule (fluorescein isothiocyanate-dextran, 70,000 mol. wt.) paracellular transport in the absence and presence of two thiol-redox protectants, the classic water-soluble N-acetyl-L-cysteine (NAC) and the novel hydrophobic N,N'-bis-2-mercaptoethyl isophthalamide (NBMI). Our results revealed that bleomycin induced cytotoxicity (lactate dehydrogenase leak), morphological alterations (rounding of cells and filipodia formation), and cytoskeletal rearrangement (actin stress fiber formation and alterations of tight junction proteins, ZO-1 and occludin) in a dose-dependent fashion. Furthermore, our study demonstrated the formation of reactive oxygen species, loss of thiols (glutathione, GSH), EC barrier dysfunction (decrease of transendothelial electrical resistance), and enhanced paracellular transport (leak) of macromolecules. The observed bleomycin-induced EC alterations were attenuated by both NAC and NBMI, revealing that the novel hydrophobic thiol-protectant, NBMI, was more effective at µM concentrations as compared to the water-soluble NAC that was effective at mM concentrations in offering protection against the bleomycin-induced EC alterations. Overall, the results of the current study suggested the central role of thiol-redox in vascular EC dysfunction associated with ILF.

Molecular and cellular mechanisms of pulmonary fibrosis

Pulmonary fibrosis is a chronic lung disease characterized by excessive accumulation of extracellular matrix (ECM) and remodeling of the lung architecture. Idiopathic pulmonary fibrosis is considered the most common and severe form of the disease, with a median survival of approximately three years and no proven effective therapy. Despite the fact that effective treatments are absent and the precise mechanisms that drive fibrosis in most patients remain incompletely understood, an extensive body of scientific literature regarding pulmonary fibrosis has accumulated over the past 35 years. In this review, we discuss three broad areas which have been explored that may be responsible for the combination of altered lung fibroblasts, loss of alveolar epithelial cells, and excessive accumulation of ECM: inflammation and immune mechanisms, oxidative stress and oxidative signaling, and procoagulant mechanisms. We discuss each of these processes separately to facilitate clarity, but certainly significant interplay will occur amongst these pathways in patients with this disease.

Bronchial brushings for investigating airway inflammation and remodelling

Asthma is the commonest medical cause for hospital admission for children in Australia, affects more than 300 million people worldwide, and is incurable, severe in large number and refractory to treatment in many. However, there have been no new significant treatments despite intense research and billions of dollars. The advancement in our understanding in this disease has been limited due to its heterogeneity, genetic complexity and has severely been hampered particularly in children by the difficulty in obtaining relevant target organ tissue. This review attempts to provide an overview of the currently used and recently developed/adapted techniques used to obtain lung tissue with specific reference to the airway epithelium.