Human placental mesenchymal stem cells of fetal origins-alleviated inflammation and fibrosis by attenuating MyD88 signaling in bleomycin-induced pulmonary fibrosis mice

Pulmonary fibrosis is a progressive lung disease that its pathogenic mechanism currently is incompletely understood. Toll-like receptor (TLR) signaling has recently been identified as a regulator of inflammation and pulmonary fibrosis. In addition, mesenchymal stem cells (MSCs) of different origins offer a great promise in treatment of idiopathic pulmonary fibrosis (IPF). However mechanisms of pathogenic roles of TLR signaling and therapeutic effects of MSCs in the IPF remain elusive. In present study, the involvement of TLR signaling and the therapeutic role of MSCs were interrogated in MyD88-deficient mice using human placental MSCs of fetal origins (hfPMSCs). The results showed an alleviated pulmonary inflammation and fibrosis in myeloid differentiation primary response gene 88 (MyD88)-deficient mice treated with bleomycin (BLM), accompanied with a reduced TGF-β signaling and production of pro-fibrotic cytokines, including TNF-α, IL-1β. An exposure of HLF1 lung fibroblasts, A549 epithelial cells and RAW264.7 macrophages to BLM led an increased expression of key components of MyD88 and TGF-β signaling cascades. Of interest, enforced expression and inhibition of MyD88 protein resulted in an enhanced and a reduced TGF-β signaling in above cells in the presence of BLM, respectively. However, the addition of TGF-β1 showed a marginally inhibitory effect on MyD88 signaling in these cells in the absence of BLM. Importantly, the administration of hfPMSCs could significantly attenuate BLM-induced pulmonary fibrosis in mice, along with a reduced hydroxyproline (HYP) deposition, MyD88 and TGF-β signaling activation, and production of pro-fibrotic cytokines. These results may suggest an importance of MyD88/TGF-β signaling axis in the tissue homeostasis and functional integrity of lung in response to injury, which may offer a novel target for treatment of pulmonary fibrosis.     

TGF-β signaling in fibrosis

Transforming growth factor β (TGF-β) is a central mediator of fibrogenesis. TGF-β is upregulated and activated in fibrotic diseases and modulates fibroblast phenotype and function, inducing myofibroblast transdifferentiation while promoting matrix preservation. Studies in a wide range of experimental models have demonstrated the involvement of the canonical activin receptor-like kinase 5/Smad3 pathway in fibrosis. Smad-independent pathways may regulate Smad activation and, under certain conditions, may directly transduce fibrogenic signals. The profibrotic actions of TGF-β are mediated, at least in part, through induction of its downstream effector, connective tissue growth factor. In light of its essential role in the pathogenesis of fibrosis, TGF-β has emerged as an attractive therapeutic target. However, the pleiotropic and multifunctional effects of TGF-β and its role in tissue homeostasis, immunity and cell proliferation raise concerns regarding potential side effects that may be caused by TGF-β blockade. This minireview summarizes the role of TGF-β signaling pathways in the fibrotic response.     

Combination Therapy with Pirfenidone plus Prednisolone Ameliorates Paraquat-Induced Pulmonary Fibrosis

Pirfenidone is known to slow the decline in vital capacity and increase survival in idiopathic pulmonary fibrosis (IPF). Besides, administration of glucocorticoids, e.g., prednisolone has been the conventional strategy to the treatment of patients with this disease, although their efficacy is under debate. Since multiple coactivated pathways are involved in the pathogenesis of IPF, combination therapy is a foundation strategy to cover many more synergetic mechanisms and increase response. The aim of the present study was to compare the therapeutic efficacy of prednisolone plus pirfenidone with pirfenidone alone in PQ-induced lung fibrosis. After development of PQ-induced lung fibrosis, pirfenidone, prednisolone, and their combination were administered for 14 consecutive days. Lung pathological lesions, along with increased hydroxyproline were determined in the paraquat group. Paraquat also caused oxidative stress and increasing the proinflammatory and profibrotic gene expression. Pirfenidone attenuated the PQ-induced pulmonary fibrosis from the analysis of antioxidant enzymes but prednisolone had no such effect. Co-treatment with pirfenidone and prednisolone suppressed lung hydroxyproline content, TGF-β1, and TNF-α; however, prednisolone alone could not suppress pulmonary fibrosis which was significantly suppressed only by pirfenidone. Pirfenidone also suppressed the increase in MMP-2 and TIMP-1 induced by PQ. All of these effects were exaggerated when pirfenidone coadministered with prednisolone. These findings suggest that pirfenidone exerts its antifibrotic effect through regulation of hydroxyproline content, oxidative stress and proinflammatory and profibrotic gene expression during the development of PQ-induced pulmonary fibrosis in rats and combination therapy with prednisolone can represent more potent therapeutic effects.     

Inhibition of glutamine transporter ASCT2 mitigates bleomycin-induced pulmonary fibrosis in mice

BackgroundIdiopathic pulmonary fibrosis (IPF) represents a fatal pulmonary disease. Its mechanisms remain unclear and effective therapies are urgently needed. Glutaminolysis is involved in IPF pathology, but little is known about the role of ASCT2 responsible for cellular uptake of glutamine in IPF. We investigated the role of ASCT2 and its therapeutic implication in IPF through knockdown of ASCT2 in mice.MethodsMouse IPF model was established through a single intratracheal administration of bleomycin, and lentivirus-coated ASCT2 siRNA was administrated into mice via caudal vein for knockdown of ASCT2. Mouse blood and lung tissues were collected for biochemical, histological, and molecular examinations.ResultsASCT2 siRNA significantly lowered ASCT2 expression in mouse lung tissues. Knockdown of ASCT2 reduced pulmonary levels of glutamic acid, α-ketoglutarate, glutathione and ATP, mitigated pulmonary histological injury, and reduced serum concentrations of pulmonary injury parameters including SP-A, SP-D, KL-6 and CCL18 in IPF mice. Moreover, serum levels of fibrotic parameters HA, LN, PC-III and IV-C were lowered by ASCT2 depletion. Collagen production and pulmonary hydroxyproline levels were also decreased by ASCT2 siRNA in IPF mice, which was concomitant with downregulation of α-smooth muscle actin, collagen type Iα1 and transforming growth factor-β receptor II. Furthermore, ASCT2 deficiency downregulated the mRNA and protein expression of inflammatory cytokines IL-1β and TNF-α as well as macrophage marker F4/80 in lung tissues of IPF mice.ConclusionsInhibition of ASCT2 effectively mitigated pulmonary injury, fibrosis and inflammation in mice with bleomycin-induced IPF. ASCT2 could be a novel therapeutic target for treatment of IPF.     

Critical role for iron accumulation in the pathogenesis of fibrotic lung disease

Increased iron levels and dysregulated iron homeostasis, or both, occur in several lung diseases. Here, the effects of iron accumulation on the pathogenesis of pulmonary fibrosis and associated lung function decline was investigated using a combination of murine models of iron overload and bleomycin-induced pulmonary fibrosis, primary human lung fibroblasts treated with iron, and histological samples from patients with or without idiopathic pulmonary fibrosis (IPF). Iron levels are significantly increased in iron overloaded transferrin receptor 2 (Tfr2) mutant mice and homeostatic iron regulator (Hfe) gene–deficient mice and this is associated with increases in airway fibrosis and reduced lung function. Furthermore, fibrosis and lung function decline are associated with pulmonary iron accumulation in bleomycin-induced pulmonary fibrosis. In addition, we show that iron accumulation is increased in lung sections from patients with IPF and that human lung fibroblasts show greater proliferation and cytokine and extracellular matrix responses when exposed to increased iron levels. Significantly, we show that intranasal treatment with the iron chelator, deferoxamine (DFO), from the time when pulmonary iron levels accumulate, prevents airway fibrosis and decline in lung function in experimental pulmonary fibrosis. Pulmonary fibrosis is associated with an increase in Tfr1⁺ macrophages that display altered phenotype in disease, and DFO treatment modified the abundance of these cells. These experimental and clinical data demonstrate that increased accumulation of pulmonary iron plays a key role in the pathogenesis of pulmonary fibrosis and lung function decline. Furthermore, these data highlight the potential for the therapeutic targeting of increased pulmonary iron in the treatment of fibrotic lung diseases such as IPF. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

MUC4 is overexpressed in idiopathic pulmonary fibrosis and collaborates with transforming growth factor β inducing fibrotic responses

Several mucins are implicated in idiopathic pulmonary fibrosis (IPF); however, there is no evidence regarding the role of MUC4 in the development of IPF. Here we demonstrated that MUC4 was overexpressed in IPF patients (n = 22) compared with healthy subjects (n = 21) and located in pulmonary arteries, bronchial epithelial cells, fibroblasts, and hyperplastic alveolar type II cells. Decreased expression of MUC4 using siRNA–MUC4 inhibited the mesenchymal/myofibroblast transformations of alveolar type II A549 cells and lung fibroblasts, as well as cell senescence and fibroblast proliferation induced by TGF-β1. The induction of the overexpression of MUC4 increased the effects of TGF-β1 on mesenchymal/myofibroblast transformations and cell senescence. MUC4 overexpression and siRNA–MUC4 gene silencing increased or decreased, respectively, the phosphorylation of TGFβRI and SMAD3, contributing to smad-binding element activation. Immunoprecipitation analysis and confocal immunofluorescence showed the formation of a protein complex between MUC4β/p-TGFβRI and p-SMAD3 in the cell membrane after TGF-β1 stimulation and in lung tissue from IPF patients. Bleomycin-induced lung fibrosis was reduced in mice transiently transfected with siRNA–MUC4. This study shows that MUC4 expression is enhanced in IPF and promotes fibrotic processes in collaboration with TGF-β1 canonical pathway that could be an attractive druggable target for human IPF.     

Effect of an immunotoxin to folate receptor �� on bleomycin-induced experimental pulmonary fibrosis

It has been suggested that alveolar and interstitial macrophages play a key role in the pathogenesis of idiopathic pulmonary fibrosis (IPF) by producing proinflammatory and/or fibrogenic cytokines. We showed that inflammatory macrophages expressed folate receptor β (FRβ) while resident macrophages in normal tissues expressed no or low levels of FRβ. In the present study, we examined the distribution of FRβ‐expressing macrophages in the lungs of patients with usual idiopathic pulmonary fibrosis (UIP) and mice with bleomycin‐induced pulmonary fibrosis (PF) and tested whether the depletion of FRβ‐expressing macrophages could suppress bleomycin‐induced PF in mice. Immunostaining with anti‐human or ‐mouse FRβ monoclonal antibody (mAb) revealed that FRβ‐expressing macrophages were present predominantly in fibrotic areas of the lungs of patients with UIP and mice with bleomycin‐induced PF. Intranasal administration of a recombinant immunotoxin, consisting of immunoglobulin heavy and light chain Fv portions of an anti‐mouse FRβ mAb and truncated Pseudomonas exotoxin A, increased survival significantly and reduced levels of total hydroxyproline and fibrosis in bleomycin‐induced PF. In immunohistochemical analysis, decreased numbers of tumour necrosis factor‐α‐, chemokines CCL2‐ and CCL12‐producing cells were observed in the immunotoxin‐treated group. These findings suggest a pathogenic role of FRβ‐expressing macrophages in IPF. Thus, targeting FRβ‐expressing macrophages may be a promising treatment of IPF.     

Secretory IgA accumulated in the airspaces of idiopathic pulmonary fibrosis and promoted VEGF,TGF-β and IL-8 production by A549 cells

Secretory IgA (SIgA) is a well-known mucosal-surface molecule in first-line defense against extrinsic pathogens and antigens. Its immunomodulatory and pathological roles have also been emphasized, but it is unclear whether it plays a pathological role in lung diseases. In the present study, we aimed to determine the distribution of IgA in idiopathic pulmonary fibrosis (IPF) lungs and whether IgA affects the functions of airway epithelial cells. We performed immunohistochemical analysis of lung sections from patients with IPF and found that mucus accumulated in the airspaces adjacent to the hyperplastic epithelia contained abundant SIgA. This was not true in the lungs of non-IPF subjects. An in-vitro assay revealed that SIgA bound to the surface of A549 cells and significantly promoted production of vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β and interleukin (IL)-8, important cytokines in the pathogenesis of IPF. Among the known receptors for IgA, A549 cells expressed high levels of transferrin receptor (TfR)/CD71. Transfection experiments with siRNA targeted against TfR/CD71 followed by stimulation with SIgA suggested that TfR/CD71 may be at least partially involved in the SIgA-induced cytokine production by A549 cells. These phenomena were specific for SIgA, distinct from IgG. SIgA may modulate the progression of IPF by enhancing synthesis of VEGF, TGF-β and IL-8.     

Methionine aminopeptidase-2 as a selective target of myofibroblasts in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, scarring lung disease characterized by fibroblast accumulation and deposition of collagen. Factors that promote growth and/or survival of fibroblasts are potential therapeutic targets. Methionine aminopeptidase 2 (MetAP2), a member of the aminopeptidase family of proteases, has been implicated in cell proliferation in a variety of cell types, but its expression and function in the lung is not known. By immunohistochemistry, MetAP2 was expressed in many cell types, including fibroblasts, in IPF lungs. Fumagillin, an irreversible inhibitor of the enzymatic activity of MetAP2, attenuated collagen deposition in the bleomycin model of acute lung injury in mice. Treatment with fumagillin caused a selective reduction in the numbers of bromodeoxyuridine (BrdU)-positive myofibroblasts, but not type II alveolar epithelial cells, macrophages, or B- and T-lymphocytes in the lungs of bleomycin-treated mice. Incubation of primary rat lung fibroblasts with either fumagillin or with short interfering RNA that targeted MetAP2 led to reduced proliferation, as assessed by incorporation of BrdU. The profibrotic growth factor, platelet-derived growth factor, increased expression of MetAP2 in rat lung fibroblasts. We propose that MetAP2 plays a role in the proliferation of fibroblasts and myofibroblasts in fibrotic lung diseases and may serve as a novel pharmacologic target in IPF.     

TGF-β signaling in fibrosis

Transforming growth factor β (TGF-β) is a central mediator of fibrogenesis. TGF-β is upregulated and activated in fibrotic diseases and modulates fibroblast phenotype and function, inducing myofibroblast transdifferentiation while promoting matrix preservation. Studies in a wide range of experimental models have demonstrated the involvement of the canonical activin receptor-like kinase 5/Smad3 pathway in fibrosis. Smad-independent pathways may regulate Smad activation and, under certain conditions, may directly transduce fibrogenic signals. The profibrotic actions of TGF-β are mediated, at least in part, through induction of its downstream effector, connective tissue growth factor. In light of its essential role in the pathogenesis of fibrosis, TGF-β has emerged as an attractive therapeutic target. However, the pleiotropic and multifunctional effects of TGF-β and its role in tissue homeostasis, immunity and cell proliferation raise concerns regarding potential side effects that may be caused by TGF-β blockade. This minireview summarizes the role of TGF-β signaling pathways in the fibrotic response.     

Essential role of stem cell factor–c‐Kit signalling pathway in bleomycin‐induced pulmonary fibrosis

Stem cell factor (SCF) and its receptor c‐Kit have been implicated in tissue remodelling and fibrosis. Alveolar fibroblasts from patients with diffuse interstitial fibrosis secrete more SCF. However, its precise role remains unclear. In this study the potential role of the SCF–c‐Kit axis in pulmonary fibrosis was examined. Fibrosis was induced by intratracheal instillation of bleomycin (BLM), which caused increased SCF levels in plasma, bronchoalveolar lavage fluid (BALF) and lung tissue, as well as increased expression by lung fibroblasts. These changes were accompanied by increased numbers of bone marrow‐derived c‐Kit⁺ cells in the lung, with corresponding depletion in bone marrow. Both recombinant SCF and lung extracts from BLM‐treated animals induced bone‐marrow cell migration, which was blocked by c‐Kit inhibitor. The migrated cells promoted myofibroblast differentiation when co‐cultured with fibroblasts, suggesting a paracrine pathogenic role. Interestingly, lung fibroblast cultures contained a subpopulation of cells that expressed functionally active c‐Kit, which were significantly greater and more responsive to SCF induction when isolated from fibrotic lungs, including those from patients with idiopathic pulmonary fibrosis (IPF). This c‐Kit⁺ subpopulation was αSMA‐negative and expressed lower levels of collagen I but significantly higher levels of TGFβ than c‐Kit‐negative cells. SCF deficiency achieved by intratracheal treatment with neutralizing anti‐SCF antibody or by use of Kitl^Sl/Kitl^Sl‐d mutant mice in vivo resulted in significant reduction in pulmonary fibrosis. Taken together, the SCF–c‐Kit pathway was activated in BLM‐injured lung and might play a direct role in pulmonary fibrosis by the recruitment of bone marrow progenitor cells capable of promoting lung myofibroblast differentiation. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Pathological differentiation of chronic hypersensitivity pneumonitis from idiopathic pulmonary fibrosis/usual interstitial pneumonia

Takemura T, Akashi T, Kamiya H, Ikushima S, Ando T, Oritsu M, Sawahata M & Ogura T
(2012) Histopathology
Pathological differentiation of chronic hypersensitivity pneumonitis from idiopathic pulmonary fibrosis/usual interstitial pneumonia Aims: To evaluate the histological characteristics differentiating chronic hypersensitivity pneumonitis (chronic HP) with a usual interstitial pneumonia (UIP)‐like pattern from idiopathic pulmonary fibrosis (IPF)/UIP. Methods and results: Surgical lung biopsy specimens from 22 patients with chronic HP diagnosed as having a UIP‐like pattern upon histological examination and 13 patients with IPF/UIP were examined and the incidences of bronchiolitis, perilobular fibrosis, centrilobular fibrosis, bridging fibrosis, organizing pneumonia, fibroblastic foci, honeycombing, granulomas, giant cells, lymphocytic alveolitis and lymphoid follicles were compared. Bronchiolitis, centrilobular fibrosis, bridging fibrosis, organizing pneumonia, granulomas, giant cells and lymphocytic alveolitis were significantly more frequent among patients with chronic HP than among patients with IPF (all P < 0.01). Conclusions: Centrilobular fibrosis, bridging fibrosis and organizing pneumonia, in addition to bronchiolitis, granulomas and giant cells, are characteristic features of chronic HP with a UIP‐like pattern. These features are therefore important in differentiating chronic HP from IPF/UIP, as management strategies differ for the two disorders.     

The immunoregulatory role of IL-35 in patients with interstitial lung disease

Pulmonary fibrosis involves various types of immune cells and soluble mediators, including TGF-β and IL-35, a recently identified heterodimeric cytokine that belongs to the IL-12 cytokine family. However, the effect of regulatory IL-35 may play an important role in fibrotic diseases. The aim of this paper is to explore the immunoregulatory role of IL-35 in the development of fibrosis in interstitial lung disease (ILD). To gain a better understanding of this issue, the concentrations of IL-35 and different profibrotic cytokines in fibrotic (F-ILD) and non-fibrotic (NF-ILD) patients by ELISA were compared to that of intracellular IL-35 and IL-17 on CD4+ T cells stimulated in the presence of BAL or with different ratios of recombinant IL-35 (rIL-35) and TGF-β (rTGF-β), which were evaluated by flow cytometry. We observed that BAL concentration of IL-35 was lower in F patients (p < 0.001) and was negatively correlated with concentrations of TGF-β (p < 0.001) and IL-17 (p < 0.001). In supplemented cell cultures, BAL from NF but not F patients enhanced the percentage of IL-35 + CD4+ T (p < 0.001) cells and decreased the percentage of IL-17 + CD4+ T cells (p < 0.001). The percentage of IL-35 + CD4+ T cells correlated positively with BAL concentration of IL-35 (p = 0.02), but correlated negatively with BAL concentrations of IL-17 (p = 0.007) and TGF-β (p = 0.01). After adjusting the concentrations of recombinant cytokines to establish a TGF-β: IL-35 ratio of 1:4, an enhanced percentage of IL-35 + CD4+ T cells (p < 0.001) but a decreased percentage of IL-17 + CD4+ T cells (p < 0.001) was observed. After adding recombinant IL-35 to the BAL from F patients until a 1:4 ratio of TGF-β: IL-35 was reached, a significantly increased percentage of IL-35 + CD4+ T cells (p < 0.001) and a decreased percentage of IL-17 + CD4+ T cells (p = 0.003) was found. These results suggest that IL-35 may induce an anti-fibrotic response, regulating the effect of TGF-β and the inflammatory response on CD4+ T cells. In addition, the TGF-β: IL-35 ratio in BAL has been shown to be a potential biomarker to predict the outcome of F patients with ILD.     

Idiopathic pulmonary fibrosis fibroblasts become resistant to Fas ligand‐dependent apoptosis via the alteration of decoy receptor 3

Idiopathic pulmonary fibrosis (IPF) is an irreversible lethal lung disease with an unknown etiology. IPF patients' lung fibroblasts express inappropriately high Akt activity, protecting them in response to an apoptosis‐inducing type I collagen matrix. FasL, a ligand for Fas, is known to be increased in the lung tissues of patients with IPF, implicated with the progression of IPF. Expression of Decoy Receptor3 (DcR3), which binds to FasL, thereby subsequently suppressing the FasL–Fas‐dependent apoptotic pathway, is frequently altered in various human disease. However, the role of DcR3 in IPF fibroblasts in regulating their viability has not been examined. We found that enhanced DcR3 expression exists in the majority of IPF fibroblasts on collagen matrices, resulting in the protection of IPF fibroblasts from FasL‐induced apoptosis. Abnormally high Akt activity suppresses GSK‐3β function, thereby accumulating the nuclear factor of activated T‐cells cytoplasmic 1 (NFATc1) in the nucleus, increasing DcR3 expression in IPF fibroblasts. This alteration protects IPF cells from FasL‐induced apoptosis on collagen. However, the inhibition of Akt or NFATc1 decreases DcR3 mRNA and protein levels, which sensitizes IPF fibroblasts to FasL‐mediated apoptosis. Furthermore, enhanced DcR3 and NFATc1 expression is mainly present in myofibroblasts in the fibroblastic foci of lung tissues derived from IPF patients. Our results showed that when IPF cells interact with collagen matrix, aberrantly activated Akt increases DcR3 expression via GSK‐3β–NFATc1 and protects IPF cells from the FasL‐dependent apoptotic pathway. These findings suggest that the inhibition of DcR3 function may be an effective approach for sensitizing IPF fibroblasts in response to FasL, limiting the progression of lung fibrosis. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Didecyldimethylammonium chloride induces pulmonary fibrosis in association with TGF-β signaling in mice

Didecyldimethylammonium chloride (DDAC) is a representative dialkyl-quaternary ammonium compound that is used as a disinfectant against several pathogens and is also used in commercial, industrial, and residential settings. We previously investigated toxicity on air way system following single instillation of DDAC to the lungs in mice, and found that DDAC causes pulmonary injury, which is associated with altered antioxidant antimicrobial responses; the inflammatory phase is accompanied or followed by fibrotic response. The present study was conducted to monitor transforming growth factor-β (TGF-β) signaling in pulmonary fibrosis induced by DDAC. Mice were intratracheally instilled with DDAC and sacrificed 1, 3, or 7 days after treatment to measure TGF-β signaling. In order to further evaluate TGF-β signaling, we treated isolated mouse lung fibroblasts with DDAC. Fibrotic foci were observed in the lungs on day 3, and were widely extended on day 7, with evidence of increased α-smooth muscle actin-positive mesenchymal cells and upregulation of Type I procollagen mRNA. Developing fibrotic foci were likely associated with increased expression of Tgf-β1 mRNA, in addition to decreased expression of Bone morphogenetic protein-7 mRNA. In fibrotic lung samples, the expression of phosphorylated SMAD2/3 was considerably higher than that of phosphorylated SMAD1/5. In isolated lung fibroblasts, the mRNA levels of Tgf-β1 were specifically increased by DDAC treatment, which prolonged phosphorylation of SMAD2/3. These effects were abolished by treatment with SD208 – a TGF-βRI kinase inhibitor. The results suggest that DDAC induces pulmonary fibrosis in association with TGF-β signaling.