Increased fibroblast telomerase expression precedes myofibroblast α-smooth muscle actin expression in idiopathic pulmonary fibrosis

Sapanisertib attenuates pulmonary fibrosis by modulating Wnt5a/mTOR signalling

Sapanisertib is an orally bioavailable ATP-dependent high-potential raptor-mTOR (TORC1) inhibitor with antineoplastic activity. Here, the impact of sapanisertib was assessed on transforming growth factor-β1 (TGF-β1)-treated L929 and A549 cells and on a rat model of bleomycin pulmonary fibrosis. First, in A549 cells treated with TGF-β1, sapanisertib significantly suppressed the TGF-β1-induced epithelial-mesenchymal transition, with elevated and reduced E-cadherin and vimentin expression, respectively. In L929 cells treated with TGF-β1, sapanisertib significantly blocked the TGF-β1-induced cell proliferation, with decreases in the extracellular matrix-related proteins collagens I and III and smooth muscle actin and in the mechanism-related proteins hypoxia-inducing factor, mTOR, p70S6K, and Wnt5a. Compared with bleomycin alone, continuous gavage administration of sapanisertib for 14 days reduced pathological scores in bleomycin-induced pulmonary fibrosis rats, with decreases in collagen deposition and in the same proteins as in L929 and A549 cells. Accordingly, our findings show that sapanisertib can ameliorate experimental pulmonary fibrosis by inhibiting Wnt5a/mTOR/HIF-1α/p70S6K.

Single-Cell Sequencing of Malignant Ascites Reveals Transcriptomic Remodeling of the Tumor Microenvironment during the Progression of Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the main cause of mortality among gynecological malignancies worldwide. Although patients with EOC undergo aggregate treatment, the prognosis is often poor. Peritoneal malignant ascites is a distinguishable clinical feature in EOC patients and plays a pivotal role in tumor progression and recurrence. The mechanisms of the tumor microenvironment (TME) in ascites in the regulation of tumor progression need to be explored. We comprehensively analyzed the transcriptomes of 4680 single cells from five EOC patients (three diagnostic samples and two recurrent samples) derived from Gene Expression Omnibus (GEO) databases. Batch effects between different samples were removed using an unsupervised deep embedding single-cell cluster algorithm. Subcluster analysis identified the different phenotypes of cells. The transition of a malignant cell state was confirmed using pseudotime analysis. The landscape of TME in malignant ascites was profiled during EOC progression. The transformation of epithelial cancer cells into mesenchymal cells was observed to lead to the emergence of related anti-chemotherapy and immune escape phenotypes. We found the activation of multiple biological pathways with the transition of tumor-associated macrophages and fibroblasts, and we identified the infiltration of CD4⁺CD25⁺ T regulatory cells in recurrent samples. The cell adhesion molecules mediated by integrin might be associated with the formation of the tumorsphere. Our study provides novel insights into the remodeling of the TME heterogeneity in malignant ascites during EOC progression, which provides evidence for identifying novel therapeutic targets and promotes the development of ovarian cancer treatment.

Telomere dysfunction implicates POT1 in patients with idiopathic pulmonary fibrosis

Exonic sequencing identified a family with idiopathic pulmonary fibrosis (IPF) containing a previously unreported heterozygous mutation in POT1 p.(L259S). The family displays short telomeres and genetic anticipation. We found that POT1(L259S) is defective in binding the telomeric overhang, nuclear accumulation, negative regulation of telomerase, and lagging strand maintenance. Patient cells containing the mutation display telomere loss, lagging strand defects, telomere-induced DNA damage, and premature senescence with G1 arrest. Our data suggest POT1(L259S) is a pathogenic driver of IPF and provide insights into gene therapy options.

The Combined Influence of Viscoelastic and Adhesive Cues on Fibroblast Spreading and Focal Adhesion Organization

Introduction

Tissue fibrosis is characterized by progressive extracellular matrix (ECM) stiffening and loss of viscoelasticity that ultimately impairs organ functionality. Cells bind to the ECM through integrins, where αv integrin engagement in particular has been correlated with fibroblast activation into contractile myofibroblasts that drive fibrosis progression. There is a significant unmet need for in vitro hydrogel systems that deconstruct the complexity of native tissues to better understand the individual and combined effects of stiffness, viscoelasticity, and integrin engagement on fibroblast behavior.

Methods

We developed hyaluronic acid hydrogels with independently tunable cell-instructive properties (stiffness, viscoelasticity, ligand presentation) to address this challenge. Hydrogels with mechanics matching normal or fibrotic lung tissue were synthesized using a combination of covalent crosslinks and supramolecular interactions to tune viscoelasticity. Cell adhesion was mediated through incorporation of either RGD peptide or engineered fibronectin fragments promoting preferential integrin engagement via αvβ3 or α5β1.

Results

On fibrosis-mimicking stiff elastic hydrogels, preferential αvβ3 engagement promoted increased spreading, actin stress fiber organization, and focal adhesion maturation as indicated by paxillin organization in human lung fibroblasts. In contrast, preferential α5β1 binding suppressed these metrics. Viscoelasticity, mimicking the mechanics of healthy tissue, largely curtailed fibroblast spreading and focal adhesion organization independent of adhesive ligand type, highlighting its role in reducing fibroblast-activating behaviors.

Conclusions

Together, these results provide new insights into how mechanical and adhesive cues collectively guide disease-relevant cell behaviors.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-021-00672-1.

Tirbanibulin Attenuates Pulmonary Fibrosis by Modulating Src/STAT3 Signaling

Tirbanibulin (KX-01) is the first clinical Src inhibitor of the novel peptidomimetic class that targets the peptide substrate site of Src providing more specificity toward the Src kinase. This study assessed the impact of KX-01 on cobalt chloride (CoCl₂)-treated L929 cells and bleomycin (BLM)-induced pulmonary fibrosis in rats to evaluate the efficacy of this compound in vitro and in vivo, respectively. In CoCl₂-treated L929 cells, KX-01 significantly reduced the expression of smooth muscle actin (α-SMA), collagen I, collagen III, hypoxia inducing factor (HIF-1α), signal transducers and transcriptional activators (p-STAT3), and p-Src. In BLM-induced pulmonary fibrosis rats, KX-01 reduced pathological scores, collagen deposition, α-SMA, collagen I, collagen III, p-Src, HIF-1α, and p-STAT3. Overall, these findings revealed that KX-01 can alleviate experimental pulmonary fibrosis via suppressing the p-SRC/p-STAT3 signaling pathways.

The dual distinct role of telomerase in repression of senescence and myofibroblast differentiation

Many aging related diseases such as cancer implicate the myofibroblast in disease progression. Furthermore genesis of the myofibroblast is associated with manifestation of cellular senescence of unclear significance. In this study we investigated the role of a common regulator, namely telomerase reverse transcriptase (TERT), in order to evaluate the potential significance of this association between both processes. We analyzed the effects of TERT overexpression or deficiency on expression of CDKN2A and ACTA2 as indicators of senescence and differentiation, respectively. We assess binding of TERT or YB-1, a repressor of both genes, to their promoters. TERT repressed both CDKN2A and ACTA2 expression, and abolished stress-induced expression of both genes. Conversely, TERT deficiency enhanced their expression. Altering CDKN2A expression had no effect on ACTA2 expression. Both TERT and YB-1 were shown to bind the CDKN2A promoter but only YB-1 was shown to bind the ACTA2 promoter. TERT overexpression inhibited CDKN2A promoter activity while stimulating YB-1 expression and activation to repress ACTA2 gene. TERT repressed myofibroblast differentiation and senescence via distinct mechanisms. The latter was associated with TERT binding to the CDKN2A promoter, but not to the ACTA2 promoter, which may require interaction with co-factors such as YB-1.

Maimendong Decoction Improves Pulmonary Function in Rats With Idiopathic Pulmonary Fibrosis by Inhibiting Endoplasmic Reticulum Stress in AECIIs

This study was designed to investigate the mechanism by which MMDD improves lung function, and observe the effect of MMDD on endoplasmic reticulum stress(ERS) in alveolar type II epithelial cells (AECIIs) of pulmonary fibrosis rats. pulmonary fibrosis animal model was established by intratracheal injection of BLM at a dose of 6mg/kg body weight. Overall, Thirty male SPF Sprague-Dawley rats were randomly divided into control group, BLM group and BLM+MMDD group. BLM+MMDD group rats were fed 24 g/kg over three weeks for twice a day on the fourteenth day after model establishment. MMDD improves pulmonary function of fibrotic rats and reduces the occurrence of endoplasmic reticulum stress in AECIIs. MMDD could significantly improve the forced vital capacity (FVC) of bleomycin-induced pulmonary fibrosis in rats. MMDD reduced the expression of GRP78 and CHOP in AECIIs, increased the secretion of surfactant protein C (SPC) by AECIIs. Moreover, the apoptosis of the fibrosis zone in the lung tissue was remarkably mitigated by administration of MMDD. The finding of this study revealed that MMDD can improve lung function in rats with pulmonary fibrosis by reducing the occurrence of ERS and cell apoptosis of AECIIs. It may provide a new method for the treatment of pulmonary fibrosis.

Kisspeptin‑13 inhibits bleomycin‑induced pulmonary fibrosis through GPR54 in mice

Kisspeptin (KP) is an amidated neurohormone that is encoded by the KiSS-1 metastasis suppressor (KISS1) gene and serves as the endogenous ligand for G protein-coupled receptor 54 (GPR54). KP is involved in the regulation of several biological functions, such as reproduction, cancer and atherogenesis. Recent data suggested that KP may induce atherosclerotic plaque progression and instability, which may be reversed by the GPR54 antagonist KP-234. Despite the KISS1 gene being previously reported as a downstream target of the classic transforming growth factor (TGF)/Smad2 signaling pathway, its role in fibrosis remains elusive. The purpose of the present study was to evaluate the role of KP-13 (a product of the KISS1 gene) in a bleomycin (BLM)-induced idiopathic pulmonary fibrosis model. Lung tissue samples were evaluated by quantitative PCR analysis, western blotting and ELISA. Daily intraperitoneal administration of KP-13 significantly ameliorated body weight loss, histopathological lung abnormalities and pulmonary collagen deposition induced by BLM. Furthermore, KP-13 downregulated the expression levels of tumor necrosis factor-α, TGF-β, collagen type I α1, actin α2 and matrix metalloproteinase 2 in BLM-treated lungs compared with BLM group. Notably, the production of α-smooth muscle actin in lung tissues, as well as the pulmonary levels of TGF-β1 and phosphorylated-Smad2/3, was reduced following treatment with KP-13. The anti-fibrotic effects of KP-13 were reversed by KP-234 (an antagonist of GPR54), but not by Cetrorelix (an antagonist of the gonadotropin-releasing hormone receptor). Furthermore, apoptosis-related proteins, such as Bax and caspase-3, were decreased, whereas Bcl-2 was markedly increased as determined by western blotting. Collectively, these data suggested that the KP/GPR54 signaling pathway may be a promising target for the treatment of idiopathic pulmonary fibrosis.

Densification of Type I Collagen Matrices as a Model for Cardiac Fibrosis

Cardiac fibrosis is a disease state characterized by excessive collagenous matrix accumulation within the myocardium that can lead to ventricular dilation and systolic failure. Current treatment options are severely lacking due in part to the poor understanding of the complexity of molecular pathways involved in cardiac fibrosis. To close this gap, in vitro model systems that recapitulate the defining features of the fibrotic cellular environment are in need. Type I collagen, a major cardiac extracellular matrix protein and the defining component of fibrotic depositions, is an attractive choice for a fibrosis model, but demonstrates poor mechanical strength due to solubility limits. However, plastic compression of collagen matrices is shown to significantly increase its mechanical properties. Here, confined compression of oligomeric, type I collagen matrices is utilized to resemble defining hallmarks seen in fibrotic tissue such as increased collagen content, fibril thickness, and bulk compressive modulus. Cardiomyocytes seeded on compressed matrices show a strong beating abrogation as observed in cardiac fibrosis. Gene expression analysis of selected fibrosis markers indicates fibrotic activation and cardiomyocyte maturation with regard to the existing literature. With these results, a promising first step toward a facile heart-on-chip model is presented to study cardiac fibrosis.

Overhydroxylation of Lysine of Collagen Increases Uterine Fibroids Proliferation: Roles of Lysyl Hydroxylases, Lysyl Oxidases, and Matrix Metalloproteinases

The role of the extracellular matrix (ECM) in uterine fibroids (UF) has recently been appreciated. Overhydroxylation of lysine residues and the subsequent formation of hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) cross-links underlie the ECM stiffness and profoundly affect tumor progression. The aim of the current study was to investigate the relationship between ECM of UF, collagen and collagen cross-linking enzymes [lysyl hydroxylases (LH) and lysyl oxidases (LOX)], and the development and progression of UF. Our results indicated that hydroxyl lysine (Hyl) and HP cross-links are significantly higher in UF compared to the normal myometrial tissues accompanied by increased expression of LH (LH2b) and LOX. Also, increased resistance to matrix metalloproteinases (MMP) proteolytic degradation activity was observed. Furthermore, the extent of collagen cross-links was positively correlated with the expression of myofibroblast marker (α-SMA), growth-promoting markers (PCNA; pERK1/2; FAK^pY397; Ki-67; and Cyclin D1), and the size of UF. In conclusion, our study defines the role of overhydroxylation of collagen and collagen cross-linking enzymes in modulating UF cell proliferation, differentiation, and resistance to MMP. These effects can establish microenvironment conducive for UF progression and thus represent potential target treatment options of UF.

Protective Effect of Atazanavir Sulphate Against Pulmonary Fibrosis In Vivo and In Vitro

Atazanavir sulphate, an antiretroviral protease inhibitor, has been used to treat HIV/AIDS, but its ability to serve as an antipulmonary fibrosis (PF) agent remains unknown. In this study, the effects of atazanavir sulphate on various aspects of PF were examined and CoCl₂ was used to induce the hypoxia-mimicking condition in vitro, including epithelial-mesenchymal transition (EMT) in A549 cells, endothelial-mesenchymal transition (EndMT) in human pulmonary microvascular endothelial cells (HPMECs), proliferation in human lung fibroblasts (HLF-1) and potential protective effects in human type I alveolar epithelial cells (AT I). Additionally, the effects of atazanavir sulphate were examined using a bleomycin (BLM)-induced pulmonary fibrosis model. After atazanavir sulphate treatment, in A549 cells and HPMECs, the expression of vimentin, HMGB1, Toll-like receptor 4 (TLR-4) and p-NF-κB decreased, while the expression of E-cadherin and VE-cadherin increased. In AT I cells, the expression of aquaporin 5 and RAGE were increased after atazanavir treatment. Proliferation of HLF-1 was reduced after atazanavir treatment, meanwhile the expression of hypoxia-inducible factor-1α (HIF-1α), prolyl hydroxylase domain protein 2 (PHD-2), HMGB1, TLR-9, p-NF-κB, collagen I and collagen III was decreased. In the BLM-induced pulmonary fibrosis rat model, atazanavir sulphate ameliorated PF by reducing pathological score, collagen deposition and the expression of α-SMA, HIF-1α, PHD-2, HMGB1, TLR-4, TLR-9 and p-NF-κB. In summary, our study supports the proposal that atazanavir sulphate may have a therapeutic potential in reducing the progression of pulmonary fibrosis by suppressing HMGB1/TLR signalling.

Radiation induced pulmonary fibrosis as a model of progressive fibrosis: Contributions of DNA damage, inflammatory response and cellular senescence genes

Purpose/Aim of Study: Studies of pulmonary fibrosis (PF) have resulted in DNA damage, inflammatory response, and cellular senescence being widely hypothesized to play a role in the progression of the disease. Utilizing these aforementioned terms, genomics databases were interrogated along with the term, "pulmonary fibrosis," to identify genes common among all 4 search terms. Findings were compared to data derived from a model of radiation-induced progressive pulmonary fibrosis (RIPF) to verify that these genes are similarly expressed, supporting the use of radiation as a model for diseases involving PF, such as human idiopathic pulmonary fibrosis (IPF).

MATERIALS AND METHODS

In an established model of RIPF, C57BL/6J mice were exposed to 12.5 Gy thorax irradiation and sacrificed at 24 hours, 1, 4, 12, and 32 weeks following exposure, and lung tissue was compared to age-matched controls by RNA sequencing.

RESULTS

Of 176 PF associated gene transcripts identified by database interrogation, 146 (>82%) were present in our experimental model, throughout the progression of RIPF. Analysis revealed that nearly 85% of PF gene transcripts were associated with at least 1 other search term. Furthermore, of 22 genes common to all four terms, 16 were present experimentally in RIPF.

CONCLUSIONS

This illustrates the validity of RIPF as a model of progressive PF/IPF based on the numbers of transcripts reported in both literature and observed experimentally. Well characterized genes and proteins are implicated in this model, supporting the hypotheses that DNA damage, inflammatory response and cellular senescence are associated with the pathogenesis of PF.

Comparative analysis of lysyl oxidase (like) family members in pulmonary fibrosis

Extracellular matrix (ECM) composition and stiffness are major driving forces for the development and persistence of fibrotic diseases. Lysyl oxidase (LOX) and LOX-like (LOXL) proteins play crucial roles in ECM remodeling due to their collagen crosslinking and intracellular functions. Here, we systematically investigated LOX/L expression in primary fibroblasts and epithelial cells under fibrotic conditions, Bleomycin (BLM) induced lung fibrosis and in human IPF tissue. Basal expression of all LOX/L family members was detected in epithelial cells and at higher levels in fibroblasts. Various pro-fibrotic stimuli broadly induced LOX/L expression in fibroblasts, whereas specific induction of LOXL2 and partially LOX was observed in epithelial cells. Immunohistochemical analysis of lung tissue from 14 IPF patients and healthy donors revealed strong induction of LOX and LOXL2 in bronchial and alveolar epithelium as well as fibroblastic foci. Using siRNA experiments we observed that LOXL2 and LOXL3 were crucial for fibroblast-to-myofibroblast transition (FMT). As FMT could only be reconstituted with an enzymatically active LOXL2 variant, we conclude that LOXL2 enzymatic function is crucial for fibroblast transdifferentiation. In summary, our study provides a comprehensive analysis of the LOX/L family in fibrotic lung disease and indicates prominent roles for LOXL2/3 in fibroblast activation and LOX/LOXL2 in IPF.

Molecular and clinical significance of fibroblast growth factor 2 (FGF2 /bFGF) in malignancies of solid and hematological cancers for personalized therapies

Fibroblast growth factor (FGF) signaling is essential for normal and cancer biology. Mammalian FGF family members participate in multiple signaling pathways by binding to heparan sulfate and FGF receptors (FGFR) with varying affinities. FGF2 is the prototype member of the FGF family and interacts with its receptor to mediate receptor dimerization, phosphorylation, and activation of signaling pathways, such as Ras-MAPK and PI3K pathways. Excessive mitogenic signaling through the FGF/FGFR axis may induce carcinogenic effects by promoting cancer progression and increasing the angiogenic potential, which can lead to metastatic tumor phenotypes. Dysregulated FGF/FGFR signaling is associated with aggressive cancer phenotypes, enhanced chemotherapy resistance and poor clinical outcomes. In vitro experimental settings have indicated that extracellular FGF2 affects proliferation, drug sensitivity, and apoptosis of cancer cells. Therapeutically targeting FGF2 and FGFR has been extensively assessed in multiple preclinical studies and numerous drugs and treatment options have been tested in clinical trials. Diagnostic assays are used to quantify FGF2, FGFRs, and downstream signaling molecules to better select a target patient population for higher efficacy of cancer therapies. This review focuses on the prognostic significance of FGF2 in cancer with emphasis on therapeutic intervention strategies for solid and hematological malignancies.

Pirfenidone and nintedanib modulate properties of fibroblasts and myofibroblasts in idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is an incurable lung disease with a poor prognosis. Fibroblasts and myofibroblasts are the key cells in the fibrotic process. Recently two drugs, pirfenidone and nintedanib, were approved for clinical use as they are able to slow down the disease progression. The mechanisms by which these two drugs act in in vitro cell systems are not known. The aim of this study was therefore to examine the effects of pirfenidone and nintedanib on fibroblasts and myofibroblasts structure and function established from patients with or without IPF.

METHODS

Stromal cells were collected and cultured from control lung (n = 4) or IPF (n = 7). The cells were treated with pirfenidone and/or nintedanib and the effect of treatment was evaluated by measuring cell proliferation, alpha smooth muscle actin (α-SMA) and fibronectin expression by Western analysis and/or immunoelectron microscopy, ultrastructural properties by transmission electron microscopy and functional properties by collagen gel contraction and invasion assays.

RESULTS

Both pirfenidone and nintedanib reduced in vitro proliferation of fibroblastic cells in a dose dependent manner. The number of cells from control lung was reduced to 47 % (p = 0.04) and of IPF cells to 42 % (p = 0.04) by 1 mM pirfenidone and correspondingly to 67 % (p = 0.04) and 68 % (p = 0.04), by 1 μM nintedanib. If both drugs were used together, a further reduced proliferation was observed. Both pirfenidone and nintedanib were able to reduce the amount of α-SMA and the myofibroblastic appearance although the level of reduction was cell line dependent. In functional assays, the effect of both drugs was also variable.

CONCLUSIONS

We conclude that the ultrastructure and function of fibroblasts and myofibroblasts are affected by pirfenidone and nintedanib. Combination of the drugs reduced cell proliferation more than either of them individually. Human lung derived cell culture systems represent a potential platform for screening and testing drugs for fibrotic diseases.

Conditional Knockout of Telomerase Reverse Transcriptase in Mesenchymal Cells Impairs Mouse Pulmonary Fibrosis

Telomerase is typically expressed in cellular populations capable of extended replication, such as germ cells, tumor cells, and stem cells, but is also induced in tissue injury, repair and fibrosis. Its catalytic component, telomerase reverse transcriptase (TERT) is induced in lung fibroblasts from patients with fibrotic interstitial lung disease and in rodents with bleomycin-induced pulmonary fibrosis. To evaluate the fibroblast specific role of TERT in pulmonary fibrosis, transgenic mice bearing a floxed TERT allele were generated, and then crossed with an inducible collagen α2(I)-Cre mouse line to generate fibroblast specific TERT conditional knockout mice. TERT-specific deficiency in mesenchymal cells caused attenuation of pulmonary fibrosis as manifested by reduced lung hydroxyproline content, type I collagen and α-smooth muscle actin mRNA levels. The TERT-deficient mouse lung fibroblasts displayed decreased cell proliferative capacity and higher susceptibility to induced apoptosis compared with control cells. Additionally TERT deficiency was associated with heightened α-smooth muscle actin expression indicative of myofibroblast differentiation. However the impairment of cell proliferation and increased susceptibility to apoptosis would cause a reduction in the myofibroblast progenitor population necessary to mount a successful myofibroblast-dependent fibrotic response. These findings identified a key role for TERT in fibroblast proliferation and survival essential for pulmonary fibrosis.

Tissue is an issue in the search for biomarkers in idiopathic pulmonary fibrosis

Biological markers, i.e., biomarkers, in lung tissue may make it possible to connect cell biological phenomena to the pathogenetic mechanisms in idiopathic pulmonary fibrosis (IPF). This review focuses on the lung tissue biomarkers, which have been compared with relevant clinical endpoints or with the most common differential diagnostic lung diseases. In addition, studies conducted on lung tissue samples and investigated by transcriptomic or proteomic methodologies have been included. Several studies have observed changes in alveolar epithelium and extracellular matrix supporting the current hypotheses of the pathogenesis of IPF. In many studies, however, alterations in inflammatory cells have been revealed, a phenomenon not currently incorporated into pathogenetic theories. Combining lung tissue material with other non-solid organs with clinically meaningful endpoints may prove to be the most beneficial approach in the search for non-invasive biomarkers.

Lung remodeling mechanisms in chronic lung diseases

PURPOSE OF REVIEW

To summarize the new knowledge on tissue remodeling in the context of lung diseases. Tissue remodeling includes changes in cells: differentiation; response to growths factors, hormones, or environmental factors; and composition of the extracellular matrix. So, can one trigger cause them all or are they independently regulated?

RECENT FINDINGS

New evidence from clinical and experimental studies strengthened the view that a susceptibility to remodeling can be initiated in early life and be re-activated by environmental triggers later in life. Many studies further support the idea that TGF-β plays the central role in the pathogenesis of remodeling and fibrosis. However, the activation pathways and the end-effect of TGF-β activation seems to be distinctive of disease and effecter cell specific patterns. The existing animal models do not properly reflect the human disease and thus have to be further improved.

SUMMARY

The central role of TGF-β on pathological mechanisms leading to remodeling and fibrosis has been further confirmed. However, the questions of why TGF-β is activated as well as its disease and cell type specific mode of action remain to be answered. Based on clinical data redefining the term 'tissue remodeling' in a disease and cell type specific way should be considered.

Telomerase and telomere length in pulmonary fibrosis

In addition to its expression in stem cells and many cancers, telomerase activity is transiently induced in murine bleomycin (BLM)-induced pulmonary fibrosis with increased levels of telomerase transcriptase (TERT) expression, which is essential for fibrosis. To extend these observations to human chronic fibrotic lung disease, we investigated the expression of telomerase activity in lung fibroblasts from patients with interstitial lung diseases (ILDs), including idiopathic pulmonary fibrosis (IPF). The results showed that telomerase activity was induced in more than 66% of IPF lung fibroblast samples, in comparison with less than 29% from control samples, some of which were obtained from lung cancer resections. Less than 4% of the human IPF lung fibroblast samples exhibited shortened telomeres, whereas less than 6% of peripheral blood leukocyte samples from patients with IPF or hypersensitivity pneumonitis demonstrated shortened telomeres. Moreover, shortened telomeres in late-generation telomerase RNA component knockout mice did not exert a significant effect on BLM-induced pulmonary fibrosis. In contrast, TERT knockout mice exhibited deficient fibrosis that was independent of telomere length. Finally, TERT expression was up-regulated by a histone deacetylase inhibitor, while the induction of TERT in lung fibroblasts was associated with the binding of acetylated histone H3K9 to the TERT promoter region. These findings indicate that significant telomerase induction was evident in fibroblasts from fibrotic murine lungs and a majority of IPF lung samples, whereas telomere shortening was not a common finding in the human blood and lung fibroblast samples. Notably, the animal studies indicated that the pathogenesis of pulmonary fibrosis was independent of telomere length.

Actin cytoskeleton redox proteome oxidation by cadmium

Epidemiological studies associate environmental cadmium (Cd) exposure with the risk of lung diseases. Although mechanisms are not fully elucidated, several studies demonstrate Cd effects on actin and actin-associated proteins. In a recent study of Cd at concentrations similar to environmental exposures, we found that redox-dependent inflammatory signaling by NF-κB was sensitive to the actin-disrupting agent, cytochalasin D. The goal of the present study was to use mass spectrometry-based redox proteomics to investigate Cd effects on the actin cytoskeleton proteome and related functional pathways in lung cells at low environmental concentrations. The results showed that Cd under conditions that did not alter total protein thiols or glutathione redox state caused significant oxidation of peptidyl Cys of proteins regulating actin cytoskeleton. Immunofluorescence microscopy of lung fibroblasts and pulmonary artery endothelial cells showed that low-dose Cd exposure stimulated filamentous actin formation and nuclear localization of destrin, an actin-depolymerizing factor. Taken together, the results show that redox states of peptidyl Cys in proteins associated with actin cytoskeleton pathways are selectively oxidized in lung by Cd at levels thought to occur from environmental exposure.