Fibrosis of two: Epithelial cell-fibroblast interactions in pulmonary fibrosis

TRIM72 promotes alveolar epithelial cell membrane repair and ameliorates lung fibrosis

Background

Chronic tissue injury was shown to induce progressive scarring in fibrotic diseases such as idiopathic pulmonary fibrosis (IPF), while an array of repair/regeneration and stress responses come to equilibrium to determine the outcome of injury at the organ level. In the lung, type I alveolar epithelial (ATI) cells constitute the epithelial barrier, while type II alveolar epithelial (ATII) cells play a pivotal role in regenerating the injured distal lungs. It had been demonstrated that eukaryotic cells possess repair machinery that can quickly patch the damaged plasma membrane after injury, and our previous studies discovered the membrane-mending role of Tripartite motif containing 72 (TRIM72) that expresses in a limited number of tissues including the lung. Nevertheless, the role of alveolar epithelial cell (AEC) repair in the pathogenesis of IPF has not been examined yet.

Method

In this study, we tested the specific roles of TRIM72 in the repair of ATII cells and the development of lung fibrosis. The role of membrane repair was accessed by saponin assay on isolated primary ATII cells and rat ATII cell line. The anti-fibrotic potential of TRIM72 was tested with bleomycin-treated transgenic mice.

Results

We showed that TRIM72 was upregulated following various injuries and in human IPF lungs. However, TRIM72 expression in ATII cells of the IPF lungs had aberrant subcellular localization. In vitro studies showed that TRIM72 repairs membrane injury of immortalized and primary ATIIs, leading to inhibition of stress-induced p53 activation and reduction in cell apoptosis. In vivo studies demonstrated that TRIM72 protects the integrity of the alveolar epithelial layer and reduces lung fibrosis.

Conclusion

Our results suggest that TRIM72 protects injured lungs and ameliorates fibrosis through promoting post-injury repair of AECs.

LncRNA GAS5 attenuates fibroblast activation through inhibiting Smad3 signaling

Transforming growth factor-β (TGF-β)-induced fibroblast activation is a key pathological event during tissue fibrosis. Long noncoding RNA (lncRNA) is a class of versatile gene regulators participating in various cellular and molecular processes. However, the function of lncRNA in fibroblast activation is still poorly understood. In this study, we identified growth arrest-specific transcript 5 (GAS5) as a novel regulator for TGF-β-induced fibroblast activation. GAS5 expression was downregulated in cultured fibroblasts by TGF-β and in resident fibroblasts from bleomycin-treated skin tissues. Overexpression of GAS5 suppressed TGF-β-induced fibroblast to myofibroblast differentiation. Mechanistically, GAS5 directly bound mothers against decapentaplegic homolog 3 (Smad3) and promoted Smad3 binding to Protein phosphatase 1A (PPM1A), a Smad3 dephosphatase, and thus accelerated Smad3 dephosphorylation in TGF-β-treated fibroblasts. In addition, GAS5 inhibited fibroblast proliferation. Importantly, local delivery of GAS5 via adenoviral vector suppressed bleomycin-induced skin fibrosis in mice. Collectively, our data revealed that GAS5 suppresses fibroblast activation and fibrogenesis through inhibiting TGF-β/Smad3 signaling, which provides a rationale for an lncRNA-based therapy to treat fibrotic diseases.

Schisandrin B attenuates bleomycin-induced pulmonary fibrosis in mice through the wingless/integrase-1 signaling pathway

Purpose/Aim: Pulmonary fibrosis (PF) is characterized by the progressive and ultimately fatal accumulation of fibroblasts and extracellular matrix in the lung that distorts its architecture and compromises its function.Objective: The present study investigated the potential protective effects of schisandrin B (Sch B) on the Wingless/Integrase-1 (Wnt) signaling pathway in attenuating inflammation and oxidative stress in ICR mice.Methods: Sixty healthy ICR mice were randomly divided into the following groups: control group, bleomycin (BLM) group, Sch B low dose (Sch B-L) group, Sch B medium dose (Sch B-M) group, Sch B high dose (Sch B-H) group, and dexamethasone (DXM) group. The expression of transforming growth factor (TGF)-β1 was examined by ELISA. In addition, the levels of superoxide dismutase (SOD), hydroxyproline (HYP), and the total antioxidant capacity (T-AOC) were determined. The protein and mRNA levels of matrix metalloproteinase 7 (MMP7) and β-catenin in mice were analyzed by western blot and quantitative real -quantitative time PCR (qRT-PCR), respectively.Results: Lung tissues from the BLM group exhibited significantly more inflammatory changes and a significantly greater number of collagen fibers than lung tissues from the control group. In addition, the lung tissues from these BLM-treated mice exhibited slightly increased MMP7 and β-catenin protein expression. Lung tissues from the Sch B-H group exhibited fewer inflammatory changes and fewer collagen fibers than lung tissues from the BLM group. Furthermore, the lung tissues from the Sch B-H mice exhibited decreased HYP and TGF-β1 levels, but increased SOD and T-AOC levels.Conclusions: The present study provided evidence that Sch B may be a potential therapeutic agent for the treatment of PF.

Pantoea agglomerans chronic exposure induces epithelial-mesenchymal transition in human lung epithelial cells and mice lungs

Pantoea agglomerans is gram-negative bacteria widely distributed in nature. It predominates in inhalable dust from grain, herbs, and flax, and was identified as the most important cause of hypersensitivity pneumonitis (HP) in eastern Poland. To better understand the molecular mechanism of HP development studies focused on the interactions between P. agglomerans and alveolar epithelial cells as well as lung tissue with particular emphasis on the epithelial-mesenchymal transition (EMT). The studies were conducted on human normal lung epithelial NL20 cells and mice strain C57BL/6J. Cells and mice underwent chronic exposure to saline extract of P. agglomerans (SE-PA). Morphological changes were evaluated under light microscopy, the concentration of fibrosis markers was examined by the ELISA method, while the expression of genes involved in EMT was evaluated by RealTime PCR. During incubation with SE-PA epithelial cells underwent conversion and assumed fibroblast phenotype characterized by a decrease in epithelial cells markers (CDH1, CLDN1, JUP) and increase in mesenchymal cells markers (FN1, VIM, CDH2). Mice lungs collected after 14 days of SE-PA treatment revealed inflammation with marked lymphocytes infiltration. The intensified inflammatory process accompanied by increased proliferation of fibrous connective tissue was noted in mice lungs after 28 days of SE-PA exposure. Histological changes correlated with an increase of fibrosis markers (hydroxyproline, collagens), downregulation of epithelial markers (Cdh1, Cldn1, Jup, Ocln) and upregulation of myofibroblasts markers (Acta2, Cdh2, Fn1, Vim). Obtained results revealed SE-PA ability to induce EMT in human lung epithelial cells and mice lung tissue, with the scale of changes proportional to the time of treatment.

Nascent Lung Organoids Reveal Epithelium- and Bone Morphogenetic Protein-mediated Suppression of Fibroblast Activation

Reciprocal epithelial-mesenchymal interactions are pivotal in lung development, homeostasis, injury, and repair. Organoids have been used to investigate such interactions, but with a major focus on epithelial responses to mesenchyme and less attention to epithelial effects on mesenchyme. In the present study, we used nascent organoids composed of human and mouse lung epithelial and mesenchymal cells to demonstrate that healthy lung epithelium dramatically represses transcriptional, contractile, and matrix synthetic functions of lung fibroblasts. Repression of fibroblast activation requires signaling via the bone morphogenetic protein (BMP) pathway. BMP signaling is diminished after epithelial injury in vitro and in vivo, and exogenous BMP4 restores fibroblast repression in injured organoids. In contrast, inhibition of BMP signaling in healthy organoids is sufficient to derepress fibroblast matrix synthetic function. Our results reveal potent repression of fibroblast activation by healthy lung epithelium and a novel mechanism by which epithelial loss or injury is intrinsically coupled to mesenchymal activation via loss of repressive BMP signaling.

Collagen-producing lung cell atlas identifies multiple subsets with distinct localization and relevance to fibrosis

Collagen-producing cells maintain the complex architecture of the lung and drive pathologic scarring in pulmonary fibrosis. Here we perform single-cell RNA-sequencing to identify all collagen-producing cells in normal and fibrotic lungs. We characterize multiple collagen-producing subpopulations with distinct anatomical localizations in different compartments of murine lungs. One subpopulation, characterized by expression of Cthrc1 (collagen triple helix repeat containing 1), emerges in fibrotic lungs and expresses the highest levels of collagens. Single-cell RNA-sequencing of human lungs, including those from idiopathic pulmonary fibrosis and scleroderma patients, demonstrate similar heterogeneity and CTHRC1-expressing fibroblasts present uniquely in fibrotic lungs. Immunostaining and in situ hybridization show that these cells are concentrated within fibroblastic foci. We purify collagen-producing subpopulations and find disease-relevant phenotypes of Cthrc1-expressing fibroblasts in in vitro and adoptive transfer experiments. Our atlas of collagen-producing cells provides a roadmap for studying the roles of these unique populations in homeostasis and pathologic fibrosis.

Recapitulating idiopathic pulmonary fibrosis related alveolar epithelial dysfunction in a human iPSC-derived air-liquid interface model

Idiopathic pulmonary fibrosis (IPF) is a fatal disease of unknown cause that is characterized by progressive fibrotic lung remodeling. An abnormal emergence of airway epithelial-like cells within the alveolar compartments of the lung, herein termed bronchiolization, is often observed in IPF. However, the origin of this dysfunctional distal lung epithelium remains unknown due to a lack of suitable human model systems. In this study, we established a human induced pluripotent stem cell (iPSC)-derived air-liquid interface (ALI) model of alveolar epithelial type II (ATII)-like cell differentiation that allows us to investigate alveolar epithelial progenitor cell differentiation in vitro. We treated this system with an IPF-relevant cocktail (IPF-RC) to mimic the pro-fibrotic cytokine milieu present in IPF lungs. Stimulation with IPF-RC during differentiation increases secretion of IPF biomarkers and RNA sequencing (RNA-seq) of these cultures reveals significant overlap with human IPF patient data. IPF-RC treatment further impairs ATII differentiation by driving a shift toward an airway epithelial-like expression signature, providing evidence that a pro-fibrotic cytokine environment can influence the proximo-distal differentiation pattern of human lung epithelial cells. In conclusion, we show for the first time, the establishment of a human model system that recapitulates aspects of IPF-associated bronchiolization of the lung epithelium in vitro.

Peroxisome Proliferator-activated Receptor-γ Deficiency Exacerbates Fibrotic Response to Mycobacteria Peptide in Murine Sarcoidosis Model

We established a murine model of multiwall carbon nanotube (MWCNT)-elicited chronic granulomatous disease that bears similarities to human sarcoidosis pathology, including alveolar macrophage deficiency of peroxisome proliferator-activated receptor γ (PPARγ). Because lymphocyte reactivity to mycobacterial antigens has been reported in sarcoidosis, we hypothesized that addition of mycobacterial ESAT-6 (early secreted antigenic target protein 6) to MWCNT might exacerbate pulmonary granulomatous pathology. MWCNTs with or without ESAT-6 peptide 14 were instilled by the oropharyngeal route into macrophage-specific PPARγ-knockout (KO) or wild-type mice. Control animals received PBS or ESAT-6. Lung tissues, BAL cells, and BAL fluid were evaluated 60 days after instillation. PPARγ-KO mice receiving MWCNT + ESAT-6 had increased granulomas and significantly elevated fibrosis (trichrome staining) compared with wild-type mice or PPARγ-KO mice that received only MWCNT. Immunostaining of lung tissues revealed elevated fibronectin and Siglec F expression on CD11c⁺ infiltrating alveolar macrophages in the presence of MWCNT + ESAT-6 compared with MWCNT alone. Analyses of BAL fluid proteins indicated increased levels of transforming growth factor (TGF)-β and the TGF-β pathway mediator IL-13 in PPARγ-KO mice that received MWCNT + ESAT-6 compared with wild-type or PPARγ-KO mice that received MWCNT. Similarly, mRNA levels of matrix metalloproteinase 9, another requisite factor for TGF-β production, was elevated in PPARγ-KO mice by MWCNT + ESAT-6. Analysis of ESAT-6 in lung tissues by mass spectrometry revealed ESAT-6 retention in lung tissues of PPARγ-KO but not wild-type mice. These data indicate that PPARγ deficiency promotes pulmonary ESAT-6 retention, exacerbates macrophage responses to MWCNT + ESAT-6, and intensifies pulmonary fibrosis. The present findings suggest that the model may facilitate understanding of the effects of environmental factors on sarcoidosis-associated pulmonary fibrosis.

IL-25/IL-33/TSLP contributes to idiopathic pulmonary fibrosis: Do alveolar epithelial cells and (myo)fibroblasts matter?

IMPACT STATEMENT

We suggest a novel modality in terms of IL-25/IL-33/TSLP's pro-fibrotic role in IPF. First, IL-25/IL-33/TSLP fully activates (myo)fibroblasts in fibroblastic foci (FF) in a paracrine-dependent manner. (IL-25/IL-33/TSLP)⁺alveolar epithelial cells-(IL-25R/IL-33R/TSLPR)⁺ (myo)fibroblasts axis may contribute greatly to the abnormal epithelial-mesenchymal crosstalk and lung fibrosis. Second, IL-25/IL-33/TSLP causes significant injury and phenotypic changes of alveolar epithelial cells in an autocrine-dependent manner. By acting directly on the two most important cells in the fibrotic process, i.e. alveolar epithelial cells and (myo)fibroblasts, we support the notion that biological therapies targeting IL-25/IL-33/TSLP will shed new light on the cure of IPF patients.

Herbal Combinational Medication of Glycyrrhiza glabra, Agastache rugosa Containing Glycyrrhizic Acid, Tilianin Inhibits Neutrophilic Lung Inflammation by Affecting CXCL2, Interleukin-17/STAT3 Signal Pathways in a Murine Model of COPD

Chronic obstructive pulmonary disease (COPD) is caused by exposure to toxic particles, such as coal fly ash (CFA), diesel-exhaust particle (DEP), and cigarette smoke (CS), leading to chronic bronchitis, mucus production, and a subsequent lung dysfunction. This study, using a mouse model of COPD, aimed to evaluate the effect of herbal combinational medication of Glycyrrhiza glabra (GG), Agastache rugosa (AR) containing glycyrrhizic acid (GA), and tilianin (TN) as active ingredients. GA, a major active component of GG, possesses a range of pharmacological and biological activities including anti-inflammatory, anti-allergic, anti-oxidative. TN is a major flavonoid that is present in AR. It has been reported to have anti-inflammatory effects of potential utility as an anti-COPD agent. The COPD in the mice model was induced by a challenge with CFA and DEP. BALB/c mice received CFA and DEP alternately three times for 2 weeks to induce COPD. The herbal mixture of GG, AR, and TN significantly decreased the number of neutrophils in the lungs and bronchoalveolar lavage (BAL) fluid. It also significantly reduced the production of C-X-C motif chemokine ligand 2 (CXCL-2), IL-17A, CXCL-1, TNF-α, symmetric dimethylarginine (SDMA) in BALF and CXCL-2, IL-17A, CXCL-1, MUC5AC, transient receptor potential vanilloid-1 (TRPV1), IL-6, COX-2, NOS-II, and TNF-α mRNA expression in the lung tissue. Notably, a combination of GG and AR was more effective at regulating such therapeutic targets than GG or AR alone. The histolopathological lung injury was alleviated by treatment with the herbal mixture and their active ingredients (especially TN). In this study, the herbal combinational mixture more effectively inhibited neutrophilic airway inflammation by regulating the expression of inflammatory cytokines and CXCL-2 by blocking the IL-17/STAT3 pathway. Therefore, a herbal mixture of GG and AR may be a potential therapeutic agent to treat COPD.

Sphingosine Kinase 1/S1P Signaling Contributes to Pulmonary Fibrosis by Activating Hippo/YAP Pathway and Mitochondrial Reactive Oxygen Species in Lung Fibroblasts

The sphingosine kinase 1 (SPHK1)/sphingosine–1–phosphate (S1P) signaling axis is emerging as a key player in the development of idiopathic pulmonary fibrosis (IPF) and bleomycin (BLM)-induced lung fibrosis in mice. Recent evidence implicates the involvement of the Hippo/Yes-associated protein (YAP) 1 pathway in lung diseases, including IPF, but its plausible link to the SPHK1/S1P signaling pathway is unclear. Herein, we demonstrate the increased co-localization of YAP1 with the fibroblast marker FSP1 in the lung fibroblasts of BLM-challenged mice, and the genetic deletion of Sphk1 in mouse lung fibroblasts (MLFs) reduced YAP1 localization in fibrotic foci. The PF543 inhibition of SPHK1 activity in mice attenuated YAP1 co-localization with FSP1 in lung fibroblasts. In vitro, TGF-β stimulated YAP1 translocation to the nucleus in primary MLFs, and the deletion of Sphk1 or inhibition with PF543 attenuated TGF-β-mediated YAP1 nuclear localization. Moreover, the PF543 inhibition of SPHK1, or the verteporfin inhibition of YAP1, decreased the TGF-β- or BLM-induced mitochondrial reactive oxygen species (mtROS) in human lung fibroblasts (HLFs) and the expression of fibronectin (FN) and alpha-smooth muscle actin (α-SMA). Furthermore, scavenging mtROS with MitoTEMPO attenuated the TGF-β-induced expression of FN and α-SMA. The addition of the S1P antibody to HLFs reduced TGF-β- or S1P-mediated YAP1 activation, mtROS, and the expression of FN and α-SMA. These results suggest a role for SPHK1/S1P signaling in TGF-β-induced YAP1 activation and mtROS generation, resulting in fibroblast activation, a critical driver of pulmonary fibrosis.

Curcumin Modulates Paraquat-Induced Epithelial to Mesenchymal Transition by Regulating Transforming Growth Factor-β (TGF-β) in A549 Cells

Paraquat (PQ), a widely used potent herbicide, generates superoxide anions and other free radicals, leading to severe toxicity and acute lung injury. PQ induces pulmonary fibrosis through epithelial to mesenchymal transition (EMT) characterized by increased number of myofibroblasts. Time-dependent PQ-induced EMT has been evaluated in present investigation where intracellular ROS levels were significantly enhanced after 24 h of PQ intoxication. Anti-inflammatory effects of curcumin have been studied where alveolar epithelial cells (A549 cells) were incubated with curcumin (30 μΜ) for 1 and 3 h before PQ intoxication (700 μM). Western blot and immunocytochemistry studies revealed that pretreatment of A549 cells with curcumin for 3 h before PQ exposure has maintained E-cadherin expression and inhibited PQ induced α-smooth-muscle actin (α-SMA) expression. Transforming growth factor-β (TGF-β) that seems to be involved in PQ-induced EMT was enhanced after PQ intoxication, but curcumin pretreatment has effectively inhibited its expression. Immunostaining studies have shown that curcumin pretreatment has significantly reduced matrix metalloproteinase-9 (MMP-9) expressions, which were elevated after PQ intoxication. These results demonstrate that curcumin can regulate PQ-induced EMT by regulating the expression of TGF-β.

Targeting MAP3K19 prevents human lung myofibroblast activation both in vitro and in a humanized SCID model of idiopathic pulmonary fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a disease with a devastating prognosis characterized by unrelenting lung scarring. Aberrant activation of lung fibroblasts is a key feature of this disease, yet the key pathways responsible for this are poorly understood. Mitogen-activated protein kinase, kinase, kinase- 19 (MAP3K19) was recently shown to be upregulated in IPF and this MAPK has a key role in target gene transcription in the TGF-β pathway. Herein, we further investigate the role of MAP3K19 in cultured normal and IPF fibroblasts and in a humanized SCID mouse model of IPF employing both short interfering (si) RNA and novel small-molecule inhibitors directed at this kinase. Targeting MAP3K19 had significant inhibitory effects on the expression of both alpha smooth muscle actin and extracellular matrix in cultured human IPF fibroblasts. Quantitative protein and biochemical assays, as well as histological analysis, showed that MAP3K19 was required for the development of lung fibrosis in SCID mice humanized with IPF lung fibroblasts. MAP3K19 was required for IPF myofibroblast differentiation, and targeting its activity attenuated the profibrotic activity of these cells both in vitro and in an adoptive transfer SCID model of pulmonary fibrosis.

Aerosol Pirfenidone Pharmacokinetics after Inhaled Delivery in Sheep: a Viable Approach to Treating Idiopathic Pulmonary Fibrosis

PURPOSE

Inhaled delivery of pirfenidone to the lungs of patients with idiopathic pulmonary fibrosis holds promise to eliminate oral-observed side effects while enhancing efficacy. This study aimed to comprehensively describe the pulmonary pharmacokinetics of inhaled aerosol pirfenidone in healthy adult sheep.

METHODS

Pirfenidone concentrations were evaluated in plasma, lung-derived lymph and epithelial lining fluid (ELF) with data subjected to non-compartmental pharmacokinetic analysis.

RESULTS

Compartmental pharmacokinetic evaluation indicated that a 49 mg lung-deposited dose delivered an ELF Cmax of 62 ± 23 mg/L, and plasma Cmax of 3.1 ± 1.7 mg/L. Further analysis revealed that plasma pirfenidone reached Tmax faster and at higher concentrations than in lymph. These results suggested inhaled pirfenidone was cleared from the alveolar interstitium via blood faster than the drug could equilibrate between the lung interstitial fluid and lung lymphatics. However, the data also suggested that a 'reservoir' of pirfenidone feeds into lung lymph at later time points (after it has largely been cleared from plasma), prolonging lung lymphatic exposure.

CONCLUSIONS

This study indicates inhaled pirfenidone efficiently deposits in ELF and is cleared from the lungs by initial absorption into plasma, followed by later equilibrium with lung interstitial and lymph fluid.

Effect of the alteration of Tribbles homologue 3 expression on epithelial‑mesenchymal transition of transforming growth factor β1‑induced mouse alveolar epithelial cells through the Wnt/β‑catenin signaling pathway

The aims of the present study were to elucidate the regulatory effect of exogenous Tribbles homologue 3 (TRB3) expression on the Wnt/β-catenin signaling pathway and epithelial-mesenchymal transition (EMT) in transforming growth factor-β1 (TGF-β1)-induced mouse alveolar epithelial cells (MLE-12) and investigate the underlying regulatory mechanisms. TRB3 expression was upregulated and downregulated using gene overexpression and RNA interference techniques, respectively. TGF-β1-stimulated MLE-12 cells were examined for EMT and activation condition of the Wnt/β-catenin signaling pathway using Cell Counting Kit-8, flow cytometry, western blotting, reverse transcription-quantitative PCR, ELISA and immunofluorescence techniques. During TGF-β1-induced EMT, TRB3 expression was found to be significantly upregulated (P<0.05). In the TRB3 overexpression group, upregulated expression of β-catenin and EMT-related genes and proteins was observed (P<0.05), and an increase in fibrosis-related factors in the cell culture supernatant was detected (P<0.05); however, the results were the opposite in the TRB3 downregulated group (P<0.05). TRB3 may be involved in the regulation of EMT in TGF-β1-induced MLE-12 cells through the Wnt/β-catenin signaling pathway.

Quartet-based inference of cell differentiation trees from ChIP-Seq histone modification data

Understanding cell differentiation-the process of generation of distinct cell-types-plays a pivotal role in developmental and evolutionary biology. Transcriptomic information and epigenetic marks are useful to elucidate hierarchical developmental relationships among cell-types. Standard phylogenetic approaches such as maximum parsimony, maximum likelihood and neighbor joining have previously been applied to ChIP-Seq histone modification data to infer cell-type trees, showing how diverse types of cells are related. In this study, we demonstrate the applicability and suitability of quartet-based phylogenetic tree estimation techniques for constructing cell-type trees. We propose two quartet-based pipelines for constructing cell phylogeny. Our methods were assessed for their validity in inferring hierarchical differentiation processes of various cell-types in H3K4me3, H3K27me3, H3K36me3, and H3K27ac histone mark data. We also propose a robust metric for evaluating cell-type trees.

TRB3 regulates pulmonary interstitial fibrosis through the MAPK signaling pathway

This study aims to investigate the effects of TRB3 on the EMT and MAPK signaling pathways in a bleomycin (BLM)-induced pulmonary fibrosis mouse model. TRB3 adenovirus vector with green fluorescent protein (GFP) and TRB3-siRNA adenovirus vector were constructed for overexpression and down-regulation of TRB3, respectively. The pulmonary fibrosis mouse model was induced by bleomycin, and then treated with adenovirus on the next day. The mice were randomly killed at the 7^th (D7), 14^th (D14) and 28^th (D28) day, respectively. The lung tissues were collected for histopathologic observations, hydroxyproline determination, Immunohistochemistry, western blot and RT-qPCR to detect the expression of TRB3 and EMT-related proteins. Overexpression of TRB3 caused more severe pulmonary fibrosis (P<0.05), while downregulation of TRB3 significantly reduced pulmonary fibrosis (P<0.05). The expression of MAPK pathway-related and EMT-related genes and proteins was markedly upregulated by TRB3 overexpression (P<0.05), but prominently downregulated by TRB3-shRNA (P<0.05). In conclusion, exogenous regulation of TRB3 may have effects on bleomycin-induced pulmonary fibrosis in mice.

p53 Expression in Lung Fibroblasts Is Linked to Mitigation of Fibrotic Lung Remodeling

Idiopathic pulmonary fibrosis (IPF) is a debilitating, incurable, and life-threatening disease. A cardinal feature of the pathogenesis of IPF is excessive extracellular matrix deposition attributable to proliferation of activated fibrotic lung fibroblasts (fLfs). To assess the underlying mechanism, we analyzed the status of the tumor suppressor protein p53 in fLfs from the lungs of IPF patients or mice with bleomycin-induced established PF. We report that basal expression of p53 is markedly reduced in fLfs. Forced expression of caveolin-1 in fLfs increased basal p53 and reduced profibrogenic proteins, including collagen-1. Transduction of fLfs with adenovirus expressing p53 reduced expression of these proteins. Conversely, inhibition of baseline p53 in control lung fibroblasts from lung tissues increased profibrogenic protein expression. Lung transduction of adenovirus expressing p53 reduced bleomycin-induced PF in wild-type or caveolin-1-deficient mice. Furthermore, treatment of fLfs or fibrotic lung tissues with caveolin-1 scaffolding domain peptide (CSP) or its fragment, CSP7, restored p53 and reduced profibrogenic proteins. Treatment of wild-type mice with i.p. CSP or CSP7 resolved bleomycin-induced PF. These peptides failed to resolve PF in inducible conditional knockout mice lacking p53 in fLfs, indicating the induction of baseline fLf p53 as the basis of the antifibrotic effects.

Location and dynamic changes of inflammation, fibrosis, and expression levels of related genes in SiO2-induced pulmonary fibrosis in rats in vivo

Silicosis is a serious occupational disease characterized by pulmonary fibrosis, and its mechanism and progression have not been fully elucidated yet. In this study, silicosis models of rat were established by a one-time dusting method, and the rats were sacrificed after 30, 60, and 120 days (herein referred to as the 30, 60, and 120 days groups, respectively). The rats without dust exposure were used as the control. The lungs were removed to observe pathological changes using hematoxylin and eosin and Masson’s trichrome staining and transmission electron microscopy, and the degree of collagen type I and III deposition in the lung was evaluated by enzyme‐linked immunosorbent assay. The levels of malondialdehyde and superoxide dismutase were measured by spectrophotometry, and the expression levels of fibrosis-related genes (transforming growth factor beta 1, type I collagen, type III collagen) were assessed by real-time quantitative polymerase chain reaction. The results suggested that the rats in the model groups exhibited obvious collagen fibrosis and that the severity of the lung injury increased as the time after exposure to SiO₂ increased. There was a significant response to lung inflammation in the model rats, especially in the 30 days group. The degree of lipid peroxidation in bronchoalveolar lavage fluid cells and lung tissues in experiment group rats significantly increased. Among the three fibrosis-related genes, transforming growth factor beta 1was elevated in both bronchoalveolar lavage fluid cells and lung tissues of the experiment group rats, while collagen type I and III were only elevated in lung tissues. Hence, we concluded that as silicosis progressed, inflammation, fibrosis, and the expression of fibrosis-related genes showed different time-dependent changes and that a number of causal relationships existed among them.

A Phase 1b Study of Vismodegib with Pirfenidone in Patients with Idiopathic Pulmonary Fibrosis

INTRODUCTION

Components of the hedgehog signaling pathway are upregulated in patients with idiopathic pulmonary fibrosis (IPF). Vismodegib, a small-molecule inhibitor of hedgehog signaling, when used in combination with currently available antifibrotic therapy, may be more efficacious than antifibrotics alone. The objective of this study was to evaluate the safety and tolerability of vismodegib plus pirfenidone in patients with IPF.

METHODS

Twenty-one patients were enrolled in a phase 1b open-label trial to receive vismodegib 150 mg plus pirfenidone 2403 mg/day once daily. Key endpoints were safety, tolerability, and pharmacokinetics. Exploratory endpoints included change from baseline to week 24 in % predicted forced vital capacity (FVC) and University of California, San Diego Shortness of Breath Questionnaire (UCSD-SOBQ) scores, as well as pharmacodynamic changes in hedgehog biomarker C-X-C motif chemokine ligand 14 (CXCL14).

RESULTS

All patients reported at least one treatment-emergent adverse event (AE), most frequently muscle spasms (76.2%). Serious AEs were reported in 14.3% of patients; one event of dehydration was considered related to vismodegib. One patient died due to IPF progression, unrelated to either treatment. More patients discontinued vismodegib than pirfenidone (42.9% vs. 33.3%, respectively). Changes from baseline to week 24 in % predicted FVC and UCSD-SOBQ scores were within known endpoint variability. In contrast to findings in basal cell carcinoma, vismodegib had no effect on circulating CXCL14 levels.

CONCLUSION

The safety profile was generally consistent with the known profiles of both drugs, with no new safety signals observed in this small cohort. There was no pharmacodynamic effect on CXCL14 levels. Future development of vismodegib for IPF may be limited due to tolerability issues.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02648048. Plain language summary available for this article.

FUNDING

F. Hoffmann-La Roche Ltd. and Genentech, Inc.

The Rho Kinase Isoforms ROCK1 and ROCK2 Each Contribute to the Development of Experimental Pulmonary Fibrosis

Pulmonary fibrosis is thought to result from dysregulated wound repair after repetitive lung injury. Many cellular responses to injury involve rearrangements of the actin cytoskeleton mediated by the two isoforms of the Rho-associated coiled-coil-forming protein kinase (ROCK), ROCK1 and ROCK2. In addition, profibrotic mediators such as transforming growth factor-β, thrombin, and lysophosphatidic acid act through receptors that activate ROCK. Inhibition of ROCK activation may be a potent therapeutic strategy for human pulmonary fibrosis. Pharmacological inhibition of ROCK using nonselective ROCK inhibitors has been shown to prevent fibrosis in animal models; however, the specific roles of each ROCK isoform are poorly understood. Furthermore, the pleiotropic effects of this kinase have raised concerns about on-target adverse effects of ROCK inhibition such as hypotension. Selective inhibition of one isoform might be a better-tolerated strategy. In the present study, we used a genetic approach to determine the roles of ROCK1 and ROCK2 in a mouse model of bleomycin-induced pulmonary fibrosis. Using ROCK1- or ROCK2-haploinsufficient mice, we found that reduced expression of either ROCK1 or ROCK2 was sufficient to protect them from bleomycin-induced pulmonary fibrosis. In addition, we found that both isoforms contribute to the profibrotic responses of epithelial cells, endothelial cells, and fibroblasts. Interestingly, ROCK1- and ROCK2-haploinsufficient mice exhibited similar protection from bleomycin-induced vascular leak, myofibroblast differentiation, and fibrosis; however, ROCK1-haploinsufficient mice demonstrated greater attenuation of epithelial cell apoptosis. These findings suggest that selective inhibition of either ROCK isoform has the potential to be an effective therapeutic strategy for pulmonary fibrosis.

Biofabrication of phenotypic pulmonary fibrosis assays

Biofabrication techniques have enabled the formation of complex models of many biological tissues. We present a framework to contextualize biofabrication techniques within a disease modeling application. Fibrosis is a progressive disease interfering with tissue structure and function, which stems from an aberrant wound healing response. Epithelial injury and clot formation lead to fibroblast invasion and activation, followed by contraction and remodeling of the extracellular matrix. These stages have healthy wound healing variants in addition to the pathogenic analogs that are seen in fibrosis. This review evaluates biofabrication of a variety of phenotypic cell-based fibrosis assays. By recapitulating different contributors to fibrosis, these assays are able to evaluate biochemical pathways and therapeutic candidates for specific stages of fibrosis pathogenesis. Biofabrication of these culture models may enable phenotypic screening for improved understanding of fibrosis biology as well as improved screening of anti-fibrotic therapeutics.

Transitional human alveolar type II epithelial cells suppress extracellular matrix and growth factor gene expression in lung fibroblasts

Epithelial-fibroblast interactions are thought to be very important in the adult lung in response to injury, but the specifics of these interactions are not well defined. We developed coculture systems to define the interactions of adult human alveolar epithelial cells with lung fibroblasts. Alveolar type II cells cultured on floating collagen gels reduced the expression of type 1 collagen (COL1A1) and α-smooth muscle actin (ACTA2) in fibroblasts. They also reduced fibroblast expression of hepatocyte growth factor (HGF), fibroblast growth factor 7 (FGF7, KGF), and FGF10. When type II cells were cultured at an air-liquid interface to maintain high levels of surfactant protein expression, this inhibitory activity was lost. When type II cells were cultured on collagen-coated tissue culture wells to reduce surfactant protein expression further and increase the expression of some type I cell markers, the epithelial cells suppressed transforming growth factor-β (TGF-β)-stimulated ACTA2 and connective tissue growth factor (CTGF) expression in lung fibroblasts. Our results suggest that transitional alveolar type II cells and likely type I cells but not fully differentiated type II cells inhibit matrix and growth factor expression in fibroblasts. These cells express markers of both type II cells and type I cells. This is probably a normal homeostatic mechanism to inhibit the fibrotic response in the resolution phase of wound healing. Defining how transitional type II cells convert activated fibroblasts into a quiescent state and inhibit the effects of TGF-β may provide another approach to limiting the development of fibrosis after alveolar injury.

The involvement of autotaxin in renal interstitial fibrosis through regulation of fibroblast functions and induction of vascular leakage

The accumulation of fibroblasts is a critical step in the development of fibrosis, and lysophosphatidic acid (LPA) promotes fibrosis by regulating multiple fibroblast functions. Autotaxin (ATX) is a key LPA-producing enzyme, and we hypothesized that ATX contributes to the development of renal interstitial fibrosis through LPA-mediated effects on fibroblast functions. In a mouse model of renal interstitial fibrosis induced by unilateral ureteral obstruction (UUO), the levels of renal ATX protein and activity increased with the progression of fibrosis in ligated kidneys, despite concurrent reductions in renal ATX mRNA. UUO enhanced vascular permeability in the renal interstitium, and ATX protein localized to areas of vascular leak, suggesting that vascular leak allowed ATX to enter the renal interstitium. In vitro studies showed that ATX induces the migration and proliferation of renal fibroblasts and enhances the vascular permeability of endothelial monolayers. Finally, pharmacological inhibition of ATX partially attenuated renal interstitial fibrosis. These results suggest that during the development of renal fibrosis, ATX accumulates in the renal interstitium and drives fibroblast accumulation and promotes renal interstitial vascular leak, thereby partially contributing to the pathogenesis of renal interstitial fibrosis. Taken together, ATX inhibition may have the potential to be a novel therapeutic strategy to combat renal interstitial fibrosis.

Spontaneous Extracellular Matrix Accumulation in a Human in vitro Model of Renal Fibrosis Is Mediated by αV Integrins

BACKGROUND

Tubulointerstitial fibrosis is a key feature of chronic kidney diseases leading to renal failure. It is characterised by the infiltration of fibroblasts and aberrant accumulation of extracellular matrix (ECM) proteins, which are associated with progressive loss of renal function. Integrins play a major role in fibrosis, but the mechanisms through which they do this are not fully understood.

OBJECTIVE

Using a complex cell system, we test the hypothesis that integrins are pro-fibrotic via regulation of functional interactions between tubular epithelial cells and renal fibroblasts.

METHOD

Contact co-culture of human primary renal proximal tubular epithelial cells and renal fibroblasts promoted the spontaneous accumulation of a mature ECM rich in interstitial collagens, which was considerably in excess of that seen in the individual mono-cultures. Both cell types persisted throughout the culture and were capable of expressing multiple ECM components.

RESULTS

While ECM accumulation was inhibited by the clinically proven anti-fibrotic, nintedanib, and was partially abrogated by transforming growth factor β neutralisation, its levels did not return to basal, indicating additional pathways were implicated in the pro-ECM response. Application of anti-integrin blocking antibodies and small molecules demonstrated a major role of the αV integrins in the ECM accumulation during fibroblast: epithelial cell interactions.

CONCLUSION

Integrin-mediated pathways can facilitate the spontaneous accumulation of ECM during fibroblast: epithelial cell interactions, and this direct renal co-culture assay system could provide a translational in vitro assay for investigating novel pathways involved in the pro-ECM response and the screening of renal anti-fibrotic agents.

Bioengineered in Vitro Tissue Model of Fibroblast Activation for Modeling Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a complex disease of unknown etiology with no current curative treatment. Modeling pulmonary fibrotic (PF) tissue has the potential to improve our understanding of IPF disease progression and treatment. Rodent animal models do not replicate human fibroblastic foci (Hum-FF) pathology, and current iterations of in vitro model systems (e.g., collagen hydrogels, polyacrylamide hydrogels, and fibrosis-on-chip systems) are unable to replicate the three-dimensional (3D) complexity and biochemical composition of human PF tissue. Herein, we fabricated a 3D bioengineered pulmonary fibrotic (Eng-PF) tissue utilizing cell laden silk collagen type I dityrosine cross-linked hydrogels and Flexcell bioreactors. We show that silk collagen type I hydrogels have superior stability and mechanical tunability compared to other hydrogel systems. Using customized Flexcell bioreactors, we reproduced Hum-FF-like pathology with airway epithelial and microvascular endothelial cells. Eng-PF tissues can model myofibroblast differentiation and permit evaluation of antifibrotic drug treatments. Further, Eng-PF tissues could be used to model different facets of IPF disease, including epithelial injury with the addition of bleomycin and cellular recruitment by perfusion of cells through the hydrogel microchannel.

IL-25 contributes to lung fibrosis by directly acting on alveolar epithelial cells and fibroblasts

IMPACT STATEMENT

Our work focused on alveolar epithelial cells (AECs)-derived type-2 cytokine (interleukin [IL]-25) in the pathogenesis of idiopathic pulmonary fibrosis (IPF). We showed that IL-25 and IL-17BR (IL-25's receptor) is upregulated in lung tissues (especially in AECs and lung fibroblasts) of IPF patients and contributes to lung fibrosis by directly activating lung fibroblasts and modulating epithelial-mesenchymal transition (EMT) of AECs. We suggest that IL-25 may be one of the master switches hidden in the milieu of abnormal epithelial-mesenchymal crosstalk. Treatment targeting IL-25 may be the potential and novel method for IPF patients.

The Hedgehog target Gli1 is not required for bleomycin-induced lung fibrosis

Sonic Hedgehog (SHH) signaling, a developmental pathway promoting lung mesenchymal expansion and differentiation during embryogenesis, has been increasingly recognized as a profibrotic factor in mature lung, where it might contribute to the pathogenesis of lung fibrosis. Pathway inhibition at the level of the downstream Gli transcription factors Gli1 and Gli2 (by GANT61) ameliorates lung fibrosis in the bleomycin model, whereas inhibition proximally at the level of HH ligand (by anti Hh antibody 5E1) or Smo (by GDC-0449) of the canonical pathway does not, implicating Gli1 and/or Gli2 as a key target. The fact that both the Gli1-labelled cell lineage and Gli1 expressing cells expand during fibrosis formation and contribute significantly to the pool of myofibroblasts in the fibrosis scars suggests a fibrogenic role for Gli1. Therefore to further dissect the roles of Gli1 and Gli2 in lung fibrosis we evaluated Gli1 KO and control mice in the bleomycin model. Monitoring of Gli1^+/+ (n = 12), Gli1^lZ/+ (n = 37) and Gli1^lZ/lZ (n = 18) mice did not reveal differences in weight loss or survival. Lung evaluation at the 21-day endpoint did not show differences in lung fibrosis formation (as judged by morphology and trichrome staining), Ashcroft score, lung collagen content, lung weight, BAL protein content or BAL cell differential count. Our data suggest that Gli1 is not required for bleomycin-induced lung fibrosis.

Alveolar-Capillary Membrane-Related Pulmonary Cells as a Target in Endotoxin-Induced Acute Lung Injury

The main function of the lungs is oxygen transport from the atmosphere into the blood circulation, while it is necessary to keep the pulmonary tissue relatively free of pathogens. This is a difficult task because the respiratory system is constantly exposed to harmful substances entering the lungs by inhalation or via the blood stream. Individual types of lung cells are equipped with the mechanisms that maintain pulmonary homeostasis. Because of the clinical significance of acute respiratory distress syndrome (ARDS) the article refers to the physiological role of alveolar epithelial cells type I and II, endothelial cells, alveolar macrophages, and fibroblasts. However, all these cells can be damaged by lipopolysaccharide (LPS) which can reach the airspaces as the major component of the outer membrane of Gram-negative bacteria, and lead to local and systemic inflammation and toxicity. We also highlight a negative effect of LPS on lung cells related to alveolar-capillary barrier and their response to LPS exposure. Additionally, we describe the molecular mechanism of LPS signal transduction pathway in lung cells.

Stem cell-based Lung-on-Chips: The best of both worlds?

Pathologies of the respiratory system such as lung infections, chronic inflammatory lung diseases, and lung cancer are among the leading causes of morbidity and mortality, killing one in six people worldwide. Development of more effective treatments is hindered by the lack of preclinical models of the human lung that can capture the disease complexity, highly heterogeneous disease phenotypes, and pharmacokinetics and pharmacodynamics observed in patients. The merger of two novel technologies, Organs-on-Chips and human stem cell engineering, has the potential to deliver such urgently needed models. Organs-on-Chips, which are microengineered bioinspired tissue systems, recapitulate the mechanochemical environment and physiological functions of human organs while concurrent advances in generating and differentiating human stem cells promise a renewable supply of patient-specific cells for personalized and precision medicine. Here, we discuss the challenges of modeling human lung pathophysiology in vitro, evaluate past and current models including Organs-on-Chips, review the current status of lung tissue modeling using human pluripotent stem cells, explore in depth how stem-cell based Lung-on-Chips may advance disease modeling and drug testing, and summarize practical consideration for the design of Lung-on-Chips for academic and industry applications.

Expression of TRB3 promotes epithelial‑mesenchymal transition of MLE‑12 murine alveolar type II epithelial cells through the TGF‑β1/Smad3 signaling pathway

The aim of the present study was to investigate whether the expression of tribbles pseudokinase 3 (TRB3) is involved in pulmonary interstitial fibrosis and to examine the possible mechanisms. The expression of TRB3 in murine alveolar type II epithelial cells (MLE‑12 cells) following transforming growth factor β1 (TGF‑β1) stimulation was assessed using various techniques, including western blot and reverse transcription‑quantitative polymerase chain reaction assays. TRB3 overexpression and downregulation models were used to evaluate the impact of TRB3 on the TGF‑β1‑induced epithelial‑mesenchymal transition (EMT) of MLE‑12 cells. The downregulation of TRB3 was induced by RNA interference. The expression of TRB3 was significantly increased in MLE‑12 cells following the activation of TGF‑β1 (P<0.05). The overexpression of TRB3 was found to promote activation of the TGF‑β1/Smad3 signaling pathway, EMT, and the upregulated expression of β‑catenin and EMT‑related genes and proteins (P<0.05), whereas the downregulation of TRB3 attenuated the promoting effect on EMT induced by TGF‑β1. In addition, the overexpression of TRB3 inhibited MLE‑12 cell proliferation by stimulating apoptosis, leading to the formation of pulmonary fibrosis (PF). The positive feedback loop demonstrated that TGF‑β1 induced the expression of TRB3, and TRB3, in turn, stimulated EMT and promoted the onset of PF through activation of the TGF‑β1/Smad3 signaling pathway. Therefore, TRB3 may promote the formation of PF through the TGF‑β1/Smad3 signaling pathway.

Secretory immunoglobulin A induces human lung fibroblasts to produce inflammatory cytokines and undergo activation

Immunoglobulin (Ig)A is the most abundant immunoglobulin in humans, and in the airway mucosa secretory IgA (sIgA) plays a pivotal role in first-line defense against invading pathogens and antigens. IgA has been reported to also have pathogenic effects, including possible worsening of the prognosis of idiopathic pulmonary fibrosis (IPF). However, the precise effects of IgA on lung fibroblasts remain unclear, and we aimed to elucidate how IgA activates human lung fibroblasts. We found that sIgA, but not monomeric IgA (mIgA), induced interleukin (IL)-6, IL-8, monocyte chemoattractant protein (MCP)-1 and granulocyte-macrophage colony-stimulating factor (GM-CSF) production by normal human lung fibroblasts (NHLFs) at both the protein and mRNA levels. sIgA also promoted proliferation of NHLFs and collagen gel contraction comparable to with transforming growth factor (TGF)-β, which is involved in fibrogenesis in IPF. Also, Western blot analysis and real-time quantitative polymerase chain reaction (PCR) revealed that sIgA enhanced production of α-smooth muscle actin (α-SMA) and collagen type I (Col I) by NHLFs. Flow cytometry showed that NHLFs bound sIgA, and among the known IgA receptors, NHLFs significantly expressed CD71 (transferrin receptor). Transfection of siRNA targeting CD71 partially but significantly suppressed cytokine production by NHLFs co-cultured with sIgA. Our findings suggest that sIgA may promote human lung inflammation and fibrosis by enhancing production of inflammatory or fibrogenic cytokines as well as extracellular matrix, inducing fibroblast differentiation into myofibroblasts and promoting human lung fibroblast proliferation. sIgA's enhancement of cytokine production may be due partially to its binding to CD71 or the secretory component.

Niclosamide alleviates pulmonary fibrosis in vitro and in vivo by attenuation of epithelial-to-mesenchymal transition, matrix proteins & Wnt/β-catenin signaling: A drug repurposing study

Drug repurposing off late has been emerging as an inspiring alternative approach to conventional, exhaustive and arduous process of drug discovery. It is a process of identifying new therapeutic values for a drug already established for the treatment of a certain condition. Our current study is aimed at repurposing the old anti-helimenthic drug Niclosamide as an anti-fibrotic drug against pulmonary fibrosis (PF). PF is most common lethal interstitial lung disease hallmarked by deposition of extracelluar matrix and scarring of lung. Heterogenous nature, untimely diagnosis and lack of appropriate treatment options make PF an inexorable lung disorder. Prevailing void in PF treatment and drug repositioning strategy of drugs kindled our interest to demonstrate the anti-fibrotic activity of Niclosamide. Our study is aimed at investigating the anti-fibrotic potential of Niclosamide in TGF-β1 induced in vitro model of PF and 21-day model of Bleomycin induced PF in vivo respectively. Our study results showed that Niclosamide holds the potential to exert anti-fibrotic effect by hampering fibroblast migration, attenuating EMT, inhibiting fibrotic signaling and by regulating WNT/β-catenin signaling as evident from protein expression studies. Our study findings can give new directions to development of Niclosamide as an anti-fibrotic agent for treatment of pulmonary fibrosis.

Modeling and measuring extracellular matrix alterations in fibrosis: challenges and perspectives for antifibrotic drug discovery

An imbalance of extracellular matrix (ECM) deposition and turnover is a hallmark of fibrotic pathologies as opposed to normal repair response to injury across several organs. Antifibrotic approaches to date have targeted multiple mechanisms and pathways involved in inflammation, angiogenesis, injury, wound repair, ECM biosynthesis, assembly, crosslinking and degradation. Many of these approaches have been unsuccessful which may in part be due to suboptimal models and the lack of validated functional ECM end points relevant to fibrosis. In addition, drug discovery and development for fibrotic diseases has been challenging due to the lack of translatability from in vivo models to the clinic. Targeting growth factor signaling pathways such as transforming growth factor beta (TGFβ), platelet-derived growth factor (PDGF), and fibroblast growth factor (FGF) are possible in simple recombinant cell models and the approval of the tyrosine kinase inhibitor, nintedanib (Ofev) is testament to the approach. However, drug targets directly impacting ECM synthesis, assembly or degradation have proven clinically intractable to date. The reasons for a lack of progress are many and include; non-traditional drug targets, lack of suitable high throughput screening assays and translational models, incomplete understanding of the role of the target. Here, we review the role of ECM in fibrosis, the challenges of ECM-targeted antifibrotic approaches, progress in the development of functional and biomarker-related ECM assays and where new translational models of fibrotic ECM remodeling could support drug discovery for fibrotic diseases.

DYRK1B regulates Hedgehog-induced microtubule acetylation

The posttranslational modification (PTM) of tubulin subunits is important for the physiological functions of the microtubule (MT) cytoskeleton. Although major advances have been made in the identification of enzymes carrying out MT-PTMs, little knowledge is available on how intercellular signaling molecules and their associated pathways regulate MT-PTM-dependent processes inside signal-receiving cells. Here we show that Hedgehog (Hh) signaling, a paradigmatic intercellular signaling system, affects the MT acetylation state in mammalian cells. Mechanistically, Hh pathway activity increases the levels of the MT-associated DYRK1B kinase, resulting in the inhibition of GSK3β through phosphorylation of Serine 9 and the subsequent suppression of HDAC6 enzyme activity. Since HDAC6 represents a major tubulin deacetylase, its inhibition increases the levels of acetylated MTs. Through the activation of DYRK1B, Hh signaling facilitates MT-dependent processes such as intracellular mitochondrial transport, mesenchymal cell polarization or directed cell migration. Taken together, we provide evidence that intercellular communication through Hh signals can regulate the MT cytoskeleton and contribute to MT-dependent processes by affecting the level of tubulin acetylation.

Fine-tuning the ubiquitin-proteasome system to treat pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is an extremely aggressive lung disease that develops almost exclusively in older individuals, carries a very poor prognosis, and lacks any truly effective therapies. The current conceptual model is that IPF develops because of an age-related decline in the ability of the lung epithelium to regenerate after injury, largely due to death or senescence of epithelial progenitor cells in the distal airways. This loss of regenerative capacity is thought to initiate a chronic and ineffective wound-healing response, characterized by persistent, low-grade lung inflammation and sustained production of collagen and other extracellular matrix materials. Despite recent advances in our understanding of IPF pathobiology, there remains a pressing need to further delineate underlying mechanisms to develop more effective therapies for this disease. In this review, we build the case that many of the manifestations of IPF result from a failure of cells to effectively manage their proteome. We propose that epithelial progenitor cells, as well as immune cells and fibroblasts, become functionally impaired, at least in part, because of an accumulation or a loss in the expression of various crucial proteins. Further, we propose that central to this defect is the dysregulation of the ubiquitin-proteasome system (UPS), which is the major protein-degradation system in eukaryotic cells. Lastly, borrowing concepts from other fields, we discuss how targeting the UPS system could be employed as a novel treatment for IPF and perhaps for other fibrotic lung diseases as well.

Differential effects of Nintedanib and Pirfenidone on lung alveolar epithelial cell function in ex vivo murine and human lung tissue cultures of pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease. Repetitive injury and reprogramming of the lung epithelium are thought to be critical drivers of disease progression, contributing to fibroblast activation, extracellular matrix remodeling, and subsequently loss of lung architecture and function. To date, Pirfenidone and Nintedanib are the only approved drugs known to decelerate disease progression, however, if and how these drugs affect lung epithelial cell function, remains largely unexplored.

Methods

We treated murine and human 3D ex vivo lung tissue cultures (3D-LTCs; generated from precision cut lung slices (PCLS)) as well as primary murine alveolar epithelial type II (pmATII) cells with Pirfenidone or Nintedanib. Murine 3D-LTCs or pmATII cells were derived from the bleomycin model of fibrosis. Early fibrotic changes were induced in human 3D-LTCs by a mixture of profibrotic factors. Epithelial and mesenchymal cell function was determined by qPCR, Western blotting, Immunofluorescent staining, and ELISA.

Results

Low μM concentrations of Nintedanib (1 μM) and mM concentrations of Pirfenidone (2.5 mM) reduced fibrotic gene expression including Collagen 1a1 and Fibronectin in murine and human 3D-LTCs as well as pmATII cells. Notably, Nintedanib stabilized expression of distal lung epithelial cell markers, especially Surfactant Protein C in pmATII cells as well as in murine and human 3D-LTCs.

Conclusions

Pirfenidone and Nintedanib exhibit distinct effects on murine and human epithelial cells, which might contribute to their anti-fibrotic action. Human 3D-LTCs represent a valuable tool to assess anti-fibrotic mechanisms of potential drugs for the treatment of IPF patients.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0876-y) contains supplementary material, which is available to authorized users.

Mitochondrial Dysfunction in Pulmonary Fibrosis

The aging of the human population has resulted in an unprecedented increase in the incidence and prevalence of age-related diseases, including those of the lung. Idiopathic pulmonary fibrosis is a disease of aging, and is characterized by a progressive decline in lung function and high mortality. Recent studies suggest that mitochondrial dysfunction, which can accompany aging phenotypes, may contribute to the pathogenesis of idiopathic pulmonary fibrosis. In this review, we explore current evidence for mitochondrial dysfunction in alveolar epithelial cells, fibroblasts, and immune cells that participate in the fibrotic process. Further, the fates of these cell populations and the potential to target mitochondrial dysfunction as a therapeutic strategy are discussed.

Cell-surface phenotyping identifies CD36 and CD97 as novel markers of fibroblast quiescence in lung fibrosis

Fibroblasts play an important role in lung homeostasis and disease. In lung fibrosis, fibroblasts adopt a proliferative and migratory phenotype, with increased expression of α-smooth muscle actin (αSMA) and enhanced secretion of extracellular matrix components. Comprehensive profiling of fibroblast heterogeneity is limited because of a lack of specific cell-surface markers. We have previously profiled the surface proteome of primary human lung fibroblasts. Here, we sought to define and quantify a panel of cluster of differentiation (CD) markers in primary human lung fibroblasts and idiopathic pulmonary fibrosis (IPF) lung tissue, using immunofluorescence and FACS analysis. Fibroblast function was assessed by analysis of replicative senescence. We observed the presence of distinct fibroblast phenotypes in vivo, characterized by various combinations of Desmin, αSMA, CD36, or CD97 expression. Most markers demonstrated stable expression over passages in vitro, but significant changes were observed for CD36, CD54, CD82, CD106, and CD140a. Replicative senescence of fibroblasts was observed from passage 10 onward. CD36- and CD97-positive but αSMA-negative cells were present in remodeled areas of IPF lungs. Transforming growth factor (TGF)-β treatment induced αSMA and collagen I expression but repressed CD36 and CD97 expression. We identified a panel of stable surface markers in human lung fibroblasts, applicable for positive-cell isolation directly from lung tissue. TGF-β exposure represses CD36 and CD97 expression, despite increasing αSMA expression; we therefore identified complex surface protein changes during fibroblast-myofibroblast activation. Coexistence of quiescence and activated fibroblast subtypes in the IPF lung suggests dynamic remodeling of fibroblast activation upon subtle changes to growth factor exposure in local microenvironmental niches.

Intratracheal instillation of coal and coal fly ash particles in mice induces DNA damage and translocation of metals to extrapulmonary tissues

Continuous exposure to coal mining particles can cause a variety of lung diseases. We aimed to evaluate the outcomes of exposure to detailed characterized coal and coal fly ash (CFA) particles on DNA, lung and extrapulmonary tissues. Coal samples (COAL11 and COAL16) and CFA samples (CFA11 and CFA16) were included in this study. Intending to enhance the combustion process COAL16 was co-fired with a mixture of fuel oil and diesel oil, producing CFA16. Male BALB/c mice were intratracheally instilled with coal and CFA particles. Measurements were done 24h later. Results showed significant rigidity and obstruction of the central airways only for animals acutely exposed to coal particles. The COAL16 group also showed obstruction of the peripheral airways. Mononuclear cells were recruited in all treatment groups and expression of cytokines, particularly TNF-α and IL-1β, was observed. Only animals exposed to COAL16 showed a significant expression of IL-6 and recruitment of polymorphonuclear cells. DNA damage was demonstrated by Comet assay for all groups. Cr, Fe and Ni were detected in liver, spleen and brain, showing the efficient translocation of metals from the bloodstream to extrapulmonary organs. These effects were associated with particle composition (oxides, hydroxides, phosphates, sulfides, sulphates, silciates, organic-metalic compounds, and polycyclic aromatic hidrocarbons) rather than their size. This work provides state of knowledge on the effects of acute exposure to coal and CFA particles on respiratory mechanics, DNA damage, translocation of metals to other organs and related inflammatory processes.

Modeling Idiopathic Pulmonary Fibrosis in Humanized Severe Combined Immunodeficient Mice

Idiopathic pulmonary fibrosis (IPF) is a fibrotic lung disease of unknown etiopathogenesis with limited therapeutic options. IPF is characterized by an abundance of fibroblasts and loss of epithelial progenitors, which cumulates in unrelenting fibrotic lung remodeling and loss of normal oxygenation. IPF has been challenging to model in rodents; nonetheless, mouse models of lung fibrosis provide clues as to the natural progression of lung injury and remodeling, but many have not been useful in predicting efficacy of therapeutics in clinical IPF. We provide a detailed methodologic description of various iterations of humanized mouse models, initiated by the i.v. injection of cells from IPF lung biopsy or explants specimens into severe combined immunodeficiency (SCID)/beige or nonobese diabetic SCID γ mice. Unlike cells from normal lung samples, IPF cells promote persistent, nonresolving lung remodeling in SCID mice. Finally, we provide examples and discuss potential advantages and pitfalls of human-specific targeting approaches in a humanized SCID model of pulmonary fibrosis.

TNFSF14 (LIGHT) Exhibits Inflammatory Activities in Lung Fibroblasts Complementary to IL-13 and TGF-β

The cytokine TNFSF14 [homologous to Lymphotoxin, exhibits Inducible expression and competes with HSV Glycoprotein D for binding to HVEM, a receptor expressed on T lymphocytes (LIGHT)] has been shown in mouse models to be important for development of lung tissue remodeling that is characteristic of asthma, idiopathic pulmonary fibrosis (IPF), and systemic sclerosis (SSc). However, its cellular targets are not fully delineated. In the present report, we show that LTβR and HVEM, the receptors for LIGHT, are constitutively expressed in primary human lung fibroblasts (HLFs). We asked whether LIGHT could promote inflammatory and remodeling-relevant activity in HLFs and how this was similar to, or distinct from, IL-13 or TGF-β, two cytokines strongly implicated in the pathogenesis of asthma, IPF, and SSc. Accumulation of myofibroblasts expressing alpha smooth muscle actin is a feature of lung inflammatory diseases. LIGHT promoted cell cycle progression and proliferation of HLFs, but not alpha smooth muscle actin expression. In contrast, TGF-β upregulated alpha smooth muscle actin but did not drive their proliferation. LIGHT also increased the gene or protein expression of a number of proinflammatory mediators, including ICAM-1 and VCAM-1, IL-6 and GM-CSF, the chemokines CCL5 and 20, and CXCL5, 11, and 12, and lung remodeling-associated proteinases MMP-9 and ADAM8. These were dependent on LTβR but not HVEM. LIGHT displayed overlapping and synergistic activities with IL-13 for a number of the activities, but LIGHT additionally enhanced the gene expression of several molecules, including the innate cytokines IL-33 and TSLP, which were not upregulated by IL-13. Our results highlight the varied and pleiotropic effects of LIGHT in HLFs. LIGHT might then be a therapeutic target for modulation of inflammation and remodeling associated with asthma and other similar diseases of the lung that involve fibroblasts.

Global Gene Expression Analysis in an in vitro Fibroblast Model of Idiopathic Pulmonary Fibrosis Reveals Potential Role for CXCL14/CXCR4

Idiopathic Pulmonary Fibrosis (IPF) is a progressive disorder that is marked by an over accumulation of activated fibroblast populations. Despite the improved understanding of many mechanisms within this disease, global gene expression analysis has few focused studies on the fibroblast, the central effector cell of progressive fibrosis. We present a unique analysis of IPF pulmonary fibroblasts as they transition through cell culture and identify in vitro altered cellular processes. Fibroblasts were isolated from diseased (n = 8) and non-diseased (n = 4) lungs. Global gene expression analysis was carried out at the initial point of isolation and after 3 weeks of culture. We identify several genes that are altered by removal of the fibroblast from the IPF environment. Comparison of this subset of genes to four previously published whole lung analyses refined our list to a small subset of key fibroblast specific genes important in IPF. Application of STRING database analysis and confirmation via in-vitro and histological assay highlights the CXCL14/CXCR4 chemokine axis with a possible role in the progression and/or activation of fibroblasts within the IPF lung. Our findings, present a possible therapeutic target for IPF and a model for the study and discovery of novel protein and processes in this terrible disease.

Adeno-Associated Virus Serotype 2 Vector-Mediated Reintroduction of microRNA-19b Attenuates Hepatic Fibrosis

Fibrotic liver injury is a significant healthcare burden in the United States. It represents a major cause of morbidity and mortality for which there are no effective Food and Drug Administration-approved treatment strategies. Fibrosis is considered a disruption of the normal wound healing responses mediated by fibroblastic cells, which are triggered and sustained by pro-fibrotic cytokines such as transforming growth factor beta 1 (TGF-β1). TGF-β1-mediated trans-differentiation of hepatic stellate cells (HSCs) from quiescent to activated myofibroblasts is a pivotal event in the development of fibrosis. Activation is accompanied by global changes in microRNA (miR) expression. It has been previously reported that miR19b is decreased in activated HSCs and contributes to increased expression of TGF-β receptor II and connective tissue growth factor, both confirmed targets of miR19b. An adeno-associated virus serotype 2 vector (AAV2) with a miR19b transgene downstream of enhanced green fluorescent protein under the murine collage alpha 1(I) promoter was developed specifically to target HSCs. Male Sprague Dawley rats (250 g) underwent sham or bile-duct ligation (BDL) surgery. Directly after BDL, rats received AAV2-miR19b, AAV2-control, or vehicle normal saline (NS) by portal-vein injection. After 2 weeks, the animals were euthanized, and blood was collected for alanine and aspartate aminotransferase, total and direct bilirubin, and alkaline phosphatase. Tissue was collected for RNA and protein extraction and histology. Fibrosis and measures of hepatic injury were significantly reduced in AAV2-miR19b-treated rats in combination with significant improvements in total and direct bilirubin. Histological analysis of collagen by PicroSirius Red staining revealed a ∼50% reduction compared to AAV2-control or NS-injected animals. Pro-fibrotic markers, smooth-muscle alpha-actin, TGF-β receptor II, and collagen alpha 2(I) mRNA and protein were significantly decreased compared to AAV2-control and NS groups. AAV2-mediated reintroduction of miR-19b, specifically expressed in HSCs, improved liver function, inhibited fibrosis, and improved measures of hepatic injury in a BDL model.

Galectin-3 Interacts with the CHI3L1 Axis and Contributes to Hermansky-Pudlak Syndrome Lung Disease

Hermansky-Pudlak syndrome (HPS) comprises a group of inherited disorders caused by mutations that alter the function of lysosome-related organelles. Pulmonary fibrosis is the major cause of morbidity and mortality in HPS-1 and HPS-4 patients. However, the mechanisms that underlie the exaggerated injury and fibroproliferative repair responses in HPS have not been adequately defined. In particular, although Galectin-3 (Gal-3) is dysregulated in HPS, its roles in the pathogenesis of HPS have not been adequately defined. In addition, although chitinase 3-like 1 (CHI3L1) and its receptors play major roles in the injury and repair responses in HPS, the ability of Gal-3 to interact with or alter the function of these moieties has not been evaluated. In this article, we demonstrate that Gal-3 accumulates in exaggerated quantities in bronchoalveolar lavage fluids, and traffics abnormally and accumulates intracellularly in lung fibroblasts and macrophages from bleomycin-treated pale ear, HPS-1-deficient mice. We also demonstrate that Gal-3 drives epithelial apoptosis when in the extracellular space, and stimulates cell proliferation and myofibroblast differentiation when accumulated in fibroblasts and M2-like differentiation when accumulated in macrophages. Biophysical and signaling evaluations also demonstrated that Gal-3 physically interacts with IL-13Rα2 and CHI3L1, and competes with TMEM219 for IL-13Rα2 binding. By doing so, Gal-3 diminishes the antiapoptotic effects of and the antiapoptotic signaling induced by CHI3L1 in epithelial cells while augmenting macrophage Wnt/β-catenin signaling. Thus, Gal-3 contributes to the exaggerated injury and fibroproliferative repair responses in HPS by altering the antiapoptotic and fibroproliferative effects of CHI3L1 and its receptor complex in a tissue compartment-specific manner.

Targeting metabolic abnormalities to reverse fibrosis in iatrogenic laryngotracheal stenosis

OBJECTIVE

Management of laryngotracheal stenosis (LTS) remains primarily surgical, with a critical need to identify targets for adjuvant therapy. Laryngotracheal stenosis scar fibroblasts exhibit a profibrotic phenotype with distinct metabolic shifts, including an increased glycolysis/oxidative phosphorylation ratio. This study examines the effects of the glutamine antagonist 6-diazo-5-oxo-l-norleucine (DON) on collagen production, gene expression, proliferation, and metabolism of human LTS-derived fibroblasts in vitro.

METHOD

Paired normal and scar-derived fibroblasts isolated from subglottic and proximal tracheal tissue in patients with iatrogenic laryngotracheal stenosis (iLTS) were cultured. Proliferation rate, gene expression, protein production, and cellular metabolism were assessed in two conditions: 1) fibroblast growth medium, and 2) fibroblast growth medium with 1 × 10-4 M DON.

RESULTS

DON treatment reduced cellular proliferation rate (n = 7, P =  0.0150). Expression of genes collagen 1 and collagen 3 both were reduced (n = 7, P =  0.0102, 0.0143, respectively). Soluble collagen production decreased (n = 7, P =  0.0056). As measured by the rate of extracellular acidification, glycolysis and glycolytic capacity decreased (n = 7, P =  0.0082, 0.0003, respectively). adenosine triphosphate (ATP) production and basal respiration decreased (n = 7, P = 0.0045, 0.0258, respectively), determined by measuring the cellular rate of oxygen consumption.

CONCLUSION

The glutamine antagonist DON reverses profibrotic changes by inhibiting both glycolysis and oxidative phosphorylation in iLTS scar fibroblasts. In contrast to untreated iLTS scar fibroblasts, collagen gene expression, protein production, metabolic rate, and proliferation were significantly reduced. These results suggest DON and/or its derivatives as strong candidates for adjuvant therapy in the management of iatrogenic laryngotracheal stenosis. Enzymes involved in glutamine metabolism inhibited by DON offer targets for future investigation.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:E59-E67, 2018.