Overexpression of cathepsin K during silica-induced lung fibrosis and control by TGF-beta

Highlighting fibroblast plasticity in lung fibrosis: the WI-38 cell line as a model for investigating the myofibroblast and lipofibroblast switch

Background: Myofibroblasts (MYFs) are generally considered the principal culprits in excessive extracellular matrix deposition and scar formation in the pathogenesis of lung fibrosis. Lipofibroblasts (LIFs), on the other hand, are defined by their lipid-storing capacity and are predominantly found in the alveolar regions of the lung. They have been proposed to play a protective role in lung fibrosis. We previously reported that a LIF to MYF reversible differentiation switch occurred during fibrosis formation and resolution. In this study, we tested whether WI-38 cells, a human embryonic lung fibroblast cell line, could be used to study fibroblast differentiation towards the LIF or MYF phenotype and whether this could be relevant for idiopathic pulmonary fibrosis (IPF). Methods: Using WI-38 cells, Fibroblast (FIB) to MYF differentiation was triggered using TGF-β1 treatment and FIB to LIF differentiation using Metformin treatment. We also analyzed the MYF to LIF and LIF to MYF differentiation by pre-treating the WI-38 cells with TGF-β1 or Metformin respectively. We used IF, qPCR and bulk RNA-Seq to analyze the phenotypic and transcriptomic changes in the cells. We correlated our in vitro transcriptome data from WI-38 cells (obtained via bulk RNA sequencing) with the transcriptomic signature of LIFs and MYFs derived from the IPF cell atlas as well as with our own single-cell transcriptomic data from IPF patients-derived lung fibroblasts (LF-IPF) cultured in vitro. We also carried out alveolosphere assays to evaluate the ability of the proposed LIF and MYF cells to support the growth of alveolar epithelial type 2 cells. Results: WI-38 cells and LF-IPF display similar phenotypical and gene expression responses to TGF-β1 and Metformin treatment. Bulk RNA-Seq analysis of WI-38 cells and LF-IPF treated with TGF-β1, or Metformin indicate similar transcriptomic changes. We also show the partial conservation of the LIF and MYF signature extracted from the Habermann et al. scRNA-seq dataset in WI-38 cells treated with Metformin or TGF-β1, respectively. Alveolosphere assays indicate that LIFs enhance organoid growth, while MYFs inhibit organoid growth. Finally, we provide evidence supporting the MYF to LIF and LIF to MYF reversible switch using WI-38 cells. Conclusions: WI-38 cells represent a versatile and reliable model to study the intricate dynamics of fibroblast differentiation towards the MYF or LIF phenotype associated with lung fibrosis formation and resolution, providing valuable insights to drive future research.

Airway epithelial overexpressed cathepsin K induces airway remodelling through epithelial-mesenchymal trophic unit activation in asthma

BACKGROUND AND PURPOSE

Airway epithelial cells (AECs) regulate the activation of epithelial-mesenchymal trophic units (EMTUs) during airway remodelling through secretion of signalling mediators. However, the major trigger and the intrinsic pathogenesis of airway remodelling is still obscure.

EXPERIMENTAL APPROACH

The differing expressed genes in airway epithelia related to airway remodelling were screened and verified by RNA-sequencing and signalling pathway analysis. Then, the effects of increased cathepsin K (CTSK) in airway epithelia on airway remodelling and EMTU activation were identified both in vitro and in vivo, and the molecular mechanism was elucidated in the EMTU model. The potential of CTSK as an an effective biomarker of airway remodelling was analysed in an asthma cohort of differing severity. Finally, an inhibitor of CTSK was administered for potential therapeutic intervention for airway remodelling in asthma.

KEY RESULTS

The expression of CTSK in airway epithelia increased significantly along with the development of airway remodelling in a house dust mite (HDM)-stressed asthma model. Increased secretion of CTSK from airway epithelia induced the activation of EMTUs by activation of the PAR2-mediated pathway. Blockade of CTSK inhibited EMTU activation and alleviated airway remodelling as an effective intervention target of airway remodelling.

CONCLUSION AND IMPLICATIONS

Increased expression of CTSK in airway epithelia is involved in the development of airway remodelling in asthma through EMTU activation, mediated partly through the PAR2-mediated signalling pathway. CTSK is a potential biomarker for airway remodelling, and may also be a useful intervention target for airway remodelling in asthma patients.

Dietary docosahexaenoic acid supplementation inhibits acute pulmonary transcriptional and autoantibody responses to a single crystalline silica exposure in lupus-prone mice

Introduction

Workplace exposure to respirable crystalline silica (cSiO2) has been epidemiologically linked to lupus. Consistent with this, repeated subchronic intranasal cSiO2 instillation in lupus-prone NZBWF1 mice induces inflammation-/autoimmune-related gene expression, ectopic lymphoid tissue (ELT), autoantibody (AAb) production in the lung within 5 to 13 wk followed systemic AAb increases and accelerated onset and progression of glomerulonephritis within 13 to 17 wk. Interestingly, dietary docosahexaenoic acid (DHA) supplementation suppresses these pathologic effects, but the underlying molecular mechanisms remain unclear.

Methods

This study aimed to test the hypothesis that dietary DHA supplementation impacts acute transcriptional and autoantibody responses in the lungs of female NZBWF1 mice 1 and 4 wk after a single high-dose cSiO2 challenge. Groups of mice were initially fed a control (Con) diet or a DHA-containing diet (10 g/kg). Cohorts of Con- and DHA-fed were subjected to a single intranasal instillation of 2.5 mg cSiO2 in a saline vehicle (Veh), while a Con-fed cohort was instilled with Veh only. At 1 and 4 wk post-instillation (PI), we compared cSiO2's effects on innate-/autoimmune-related gene expression and autoantibody (AAb) in lavage fluid/lungs of Con- and DHA-fed mice and related these findings to inflammatory cell profiles, histopathology, cell death, and cytokine/chemokine production.

Results

DHA partially alleviated cSiO2-induced alterations in total immune cell and lymphocyte counts in lung lavage fluid. cSiO2-triggered dead cell accumulation and levels of inflammation-associated cytokines and IFN-stimulated chemokines were more pronounced in Con-fed mice than DHA-fed mice. Targeted multiplex transcriptome analysis revealed substantial upregulation of genes associated with autoimmune pathways in Con-fed mice in response to cSiO2 that were suppressed in DHA-fed mice. Pathway analysis indicated that DHA inhibited cSiO2 induction of proinflammatory and IFN-regulated gene networks, affecting key upstream regulators (e.g., TNFα, IL-1β, IFNAR, and IFNγ). Finally, cSiO2-triggered AAb responses were suppressed in DHA-fed mice.

Discussion

Taken together, DHA mitigated cSiO2-induced upregulation of pathways associated with proinflammatory and IFN-regulated gene responses within 1 wk and reduced AAb responses by 4 wk. These findings suggest that the acute short-term model employed here holds substantial promise for efficient elucidation of the molecular mechanisms through which omega-3 PUFAs exert protective effects against cSiO2-induced autoimmunity.

Lung macrophages utilize unique cathepsin K-dependent phagosomal machinery to degrade intracellular collagen

Resident tissue macrophages are organ-specialized phagocytes responsible for the maintenance and protection of tissue homeostasis. It is well established that tissue diversity is reflected by the heterogeneity of resident tissue macrophage origin and phenotype. However, much less is known about tissue-specific phagocytic and proteolytic macrophage functions. Here, using a quantitative proteomics approach, we identify cathepsins as key determinants of phagosome maturation in primary peritoneum-, lung-, and brain-resident macrophages. The data further uncover cathepsin K (CtsK) as a molecular marker for lung phagosomes required for intracellular protein and collagen degradation. Pharmacological blockade of CtsK activity diminished phagosomal proteolysis and collagenolysis in lung-resident macrophages. Furthermore, profibrotic TGF-β negatively regulated CtsK-mediated phagosomal collagen degradation independently from classical endocytic-proteolytic pathways. In humans, phagosomal CtsK activity was reduced in COPD lung macrophages and non-COPD lung macrophages exposed to cigarette smoke extract. Taken together, this study provides a comprehensive map of how peritoneal, lung, and brain tissue environment shapes phagosomal composition, revealing CtsK as a key molecular determinant of lung phagosomes contributing to phagocytic collagen clearance in lungs.

Pulmonary Toxicity of Silica Linked to Its Micro- or Nanometric Particle Size and Crystal Structure: A Review

Silicon dioxide (SiO2) is a mineral compound present in the Earth’s crust in two mineral forms: crystalline and amorphous. Based on epidemiological and/or biological evidence, the pulmonary effects of crystalline silica are considered well understood, with the development of silicosis, emphysema, chronic bronchitis, or chronic obstructive pulmonary disease. The structure and capacity to trigger oxidative stress are recognized as relevant determinants in crystalline silica’s toxicity. In contrast, natural amorphous silica was long considered nontoxic, and was often used as a negative control in experimental studies. However, as manufactured amorphous silica nanoparticles (or nanosilica or SiNP) are becoming widely used in industrial applications, these paradigms must now be reconsidered at the nanoscale (<100 nm). Indeed, recent experimental studies appear to point towards significant toxicity of manufactured amorphous silica nanoparticles similar to that of micrometric crystalline silica. In this article, we present an extensive review of the nontumoral pulmonary effects of silica based on in vitro and in vivo experimental studies. The findings of this review are presented both for micro- and nanoscale particles, but also based on the crystalline structure of the silica particles.

A suitable silicosis mouse model was constructed by repeated inhalation of silica dust via nose

Silicosis as the serious occupational disease is highly necessary to construct a suitable mouse model for disclosing mechanism of occurrence and development in this disease. Here, the volume-effect relationship and volume-based survival curves in mice who inhaled silica suspension intranasally were analyzed. Notable, the optimal volume 80 μl repeated-inhalation by nose to silica suspension in the inbred mouse C57BL/6 J with the highest susceptibility to silicosis led to a great entrance into the lung and a high survival rate after instillation. After repeated-exposure to 20 mg/mL, 80 μl silica for 16 days and then fed without silica exposure until 31 days, weight of mice showed a trend of first decrease and then recover. Moreover, the degree of pulmonary inflammation and fibrosis in mice were analyzed by pathological and immunohistochemistry staining. Transforming growth factor-beta (TGF-β), smooth muscle alpha-actin (α-SMA) and collagen type-I (collagen I, Col-I) were significantly increased in the silica-exposed mouse lung at post-exposure day 16 compared with the controls. Sirius red stain and Micro-CT analysis showed that lung fibrosis formed at post-exposure day 31. This study highlights the critical importance of perfusion volume and repeated nasal drops in inducing inflammatory response and pulmonary fibrosis in silicosis.

Identification of Hub Genes and Pathways Associated With Idiopathic Pulmonary Fibrosis via Bioinformatics Analysis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease whose etiology remains unknown. The purpose of this study was to explore hub genes and pathways related to IPF development and prognosis. Multiple gene expression datasets were downloaded from the Gene Expression Omnibus database. Weighted correlation network analysis (WGCNA) was performed and differentially expressed genes (DEGs) identified to investigate Hub modules and genes correlated with IPF. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and protein-protein interaction (PPI) network analysis were performed on selected key genes. In the PPI network and cytoHubba plugin, 11 hub genes were identified, including ASPN, CDH2, COL1A1, COL1A2, COL3A1, COL14A1, CTSK, MMP1, MMP7, POSTN, and SPP1. Correlation between hub genes was displayed and validated. Expression levels of hub genes were verified using quantitative real-time PCR (qRT-PCR). Dysregulated expression of these genes and their crosstalk might impact the development of IPF through modulating IPF-related biological processes and signaling pathways. Among these genes, expression levels of COL1A1, COL3A1, CTSK, MMP1, MMP7, POSTN, and SPP1 were positively correlated with IPF prognosis. The present study provides further insights into individualized treatment and prognosis for IPF.

Podoconiosis - From known to unknown: Obstacles to tackle

Podoconiosis is a non-filarial and non-communicable disease leading to lymphedema of the lower limbs. Worldwide, 4 million individuals live with podoconiosis, which is accompanied by disability and painful intermittent acute inflammatory episodes that attribute to significant disability adjusted life years (DALYs). Different risk factors like contact with volcanic red clay soil, high altitude (above 1000 m), high seasonal rainfall (above 1000 mm/year) and occupation (e.g., subsistence farmer) are associated with the risk of podoconiosis. Although podoconiosis was described to be endemic in 32 countries in Africa, parts of Latin America and South East Asia, knowledge about related genetics, pathophysiology, immunology and especially the causing molecule(s) in the soil remain uncertain. Thus, podoconiosis can be considered as one of the most neglected diseases. This review provides an overview about this non-filarial related geochemical disease and aim to present perspectives and future directions that might be important for better understanding of the disease, prospect for point-of-care diagnosis, achieving protection and developing novel treatment strategies.

Rapid Induction of Pulmonary Inflammation, Autoimmune Gene Expression, and Ectopic Lymphoid Neogenesis Following Acute Silica Exposure in Lupus-Prone Mice

Occupational exposure to crystalline silica (cSiO2) is etiologically associated with systemic lupus erythematosus (lupus) and other autoimmune diseases. cSiO2's autoimmune effects in humans can be mimicked chronically in female lupus-prone NZBWF1 mice following repeated exposure to the particle. However, the immediate and short-term effects of cSiO2 in this widely used model of autoimmune disease are not well-understood. In the present study, we tested the hypothesis that a single acute cSiO2 dose triggers early presentation of cellular, histopathological, transcriptomic, and protein biomarkers of inflammation and autoimmunity in lupus-prone mice. Eight-week old female NZBWF1 mice were intranasally instilled once with 2.5 mg cSiO2 or saline vehicle and necropsied at 1, 7, 14, 21, and 28 d post-instillation (PI). Analyses of bronchoalveolar lavage fluid (BALF) and lung tissue revealed that by 7 d PI, acute cSiO2 exposure persistently provoked: (i) robust recruitment of macrophages, neutrophils, and lymphocytes into the alveoli, (ii) cell death as reflected by increased protein, double-stranded DNA, and lactate dehydrogenase activity, (iii) elevated secretion of the cytokines IL-1α, IL-1β, IL-18, TNF-α, IL-6, MCP-1, and B cell activation factor (BAFF), and (iv) upregulation of genes associated with chemokines, proinflammatory cytokines, lymphocyte activation, and type I interferon signaling. The appearance of these endpoints was subsequently followed by the emergence in the lung of organized CD3+ T cells (14 d PI) and CD45R+ B cells (21 d PI) that were indicative of ectopic lymphoid structure (ELS) development. Taken together, acute cSiO2 exposure triggered a rapid onset of autoimmune disease pathogenesis that was heralded in the lung by unresolved inflammation and cell death, proinflammatory cytokine production, chemokine-driven recruitment of leukocytes, an interferon response signature, B and T cell activation, and ELS neogenesis. This short-term murine model provides valuable new insight into potential early mechanisms of cSiO2-induced lupus flaring and, furthermore, offers a rapid venue for evaluating interventions against respirable particle-triggered inflammation and autoimmunity.

Elevated Expression of Cathepsin K in Periodontal Ligament Fibroblast by Inflammatory Cytokines Accelerates Osteoclastogenesis via Paracrine Mechanism in Periodontal Disease

Cathepsin K (CTSK) is a cysteine protease that is mainly produced from mature osteoclasts and contributes to the destruction of connective tissues and mineralized matrix as a consequence of periodontal disease (PD). However, few studies have reported its regulatory role in osteoclastogenesis-supporting cells in inflammatory conditions. Here, we investigated the role of CTSK in osteoclastogenesis-supporting cells, focusing on the modulation of paracrine function. Microarray data showed that CTSK was upregulated in PD patients compared with healthy individuals, which was further supported by immunohistochemistry and qPCR analyses performed with human gingival tissues. The expression of CTSK in the osteoclastogenesis-supporting cells, including dental pulp stem cells, gingival fibroblasts, and periodontal ligament fibroblasts (PDLFs) was significantly elevated by treatment with inflammatory cytokines such as TNFα and IL-1β. Moreover, TNFα stimulation potentiated the PDLF-mediated osteoclastogenesis of bone marrow-derived macrophages. Interestingly, small interfering RNA-mediated silencing of CTSK in PDLF noticeably attenuated the TNFα-triggered upregulation of receptor activator of nuclear factor kappa-B ligand (RANKL), macrophage colony-stimulating factor, and RANKL/osteoprotegerin ratio, thereby abrogating the enhanced osteoclastogenesis-supporting activity of PDLF. Collectively, these results suggest a novel role of CTSK in the paracrine function of osteoclastogenesis-supporting cells in periodontal disease.

Comparative proteomic analysis of silica-induced pulmonary fibrosis in rats based on tandem mass tag (TMT) quantitation technology

Silicosis is a systemic disease characterized by chronic persistent inflammation and incurable pulmonary fibrosis with the underlying molecular mechanisms to be fully elucidated. In this study, we employed tandem mass tag (TMT) based on quantitative proteomics technology to detect differentially expressed proteins (DEPs) in lung tissues of silica-exposed rats. A total of 285 DEPs (145 upregulated and 140 downregulated) were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to predict the biological pathway and functional classification of the proteins. Results showed that these DEPs were mainly enriched in the phagosome, lysosome function, complement and the coagulation cascade, glutathione metabolism, focal adhesion and ECM-receptor interactions. To validate the proteomics data, we selected and analyzed the expression trends of six proteins including CD14, PSAP, GM2A, COL1A1, ITGA8 and CLDN5 using parallel reaction monitoring (PRM). The consistent result between PRM and TMT indicated the reliability of our proteomic data. These findings will help to reveal the pathogenesis of silicosis and provide potential therapeutic targets. Data are available via ProteomeXchange with identifier PXD020625.

Regulation of the Proteolytic Activity of Cysteine Cathepsins by Oxidants

Besides their primary involvement in the recycling and degradation of proteins in endo-lysosomal compartments and also in specialized biological functions, cysteine cathepsins are pivotal proteolytic contributors of various deleterious diseases. While the molecular mechanisms of regulation via their natural inhibitors have been exhaustively studied, less is currently known about how their enzymatic activity is modulated during the redox imbalance associated with oxidative stress and their exposure resistance to oxidants. More specifically, there is only patchy information on the regulation of lung cysteine cathepsins, while the respiratory system is directly exposed to countless exogenous oxidants contained in dust, tobacco, combustion fumes, and industrial or domestic particles. Papain-like enzymes (clan CA, family C1, subfamily C1A) encompass a conserved catalytic thiolate-imidazolium pair (Cys25-His159) in their active site. Although the sulfhydryl group (with a low acidic pKa) is a potent nucleophile highly susceptible to chemical modifications, some cysteine cathepsins reveal an unanticipated resistance to oxidative stress. Besides an introductory chapter and peculiar attention to lung cysteine cathepsins, the purpose of this review is to afford a concise update of the current knowledge on molecular mechanisms associated with the regulation of cysteine cathepsins by redox balance and by oxidants (e.g., Michael acceptors, reactive oxygen, and nitrogen species).

Cathepsin K: The Action in and Beyond Bone

Cathepsin K (CatK) is one of the most potent proteases in lysosomal cysteine proteases family, of which main function is to mediate bone resorption. Currently, CatK is among the most attractive targets for anti-osteoporosis drug development. Although many pharmaceutical companies are working on the development of selective inhibitors for CatK, there is no FDA approved drug till now. Odanacatib (ODN) developed by Merck & Co. is the only CatK inhibitor candidate which demonstrated high therapeutic efficacy in patients with postmenopausal osteoporosis in Phase III clinical trials. Unfortunately, the development of ODN was finally terminated due to the cardio-cerebrovascular adverse effects. Therefore, it arouses concerns on the undesirable CatK inhibition in non-bone sites. It is known that CatK has far-reaching actions throughout various organs besides bone. Many studies have also demonstrated the involvement of CatK in various diseases beyond the musculoskeletal system. This review not only summarized the functional roles of CatK in bone and beyond bone, but also discussed the potential relevance of the CatK action beyond bone to the adverse effects of inhibiting CatK in non-bone sites.

Differential Roles of Cysteinyl Cathepsins in TGF-β Signaling and Tissue Fibrosis

Transforming growth factor beta (TGF-β) signaling contributes to tissue fibrosis. Here we demonstrate that TGF-β enhances CatS and CatK expression but reduces CatB and CatL expression in mouse kidney tubular epithelial cells (TECs). CatS- and CatK deficiency reduces TEC nuclear membrane importer importin-β expression, Smad-2/3 activation, and extracellular matrix (ECM) production. Yet CatB- and CatL-deficiency displays the opposite observations with reduced nuclear membrane exporter RanBP3 expression. CatS and CatK form immunocomplexes with the importin-β and RanBP3 more effectively than do CatB and CatL. On the plasma membrane, CatS and CatK preferentially form immunocomplexes with and activate TGF-β receptor-2, whereas CatB and CatL form immunocomplexes with and inactivate TGF-β receptor-1. Unilateral ureteral obstruction-induced renal injury tests differential cathepsin activities in TGF-β signaling and tissue fibrosis. CatB- or CatL-deficiency exacerbates fibrosis, whereas CatS- or CatK-deficiency protects kidneys from fibrosis. These cathepsins exert different effects in the TGF-β signaling cascade independent of their proteolytic properties.

Role of Nephronectin in Pathophysiology of Silicosis

Silicosis is a typical form of pneumoconiosis and is characterized as a type of lung fibrosis. Silica particles are captured and recognized upon by alveolar macrophages via the macrophage receptor with collagenous structure (MARCO) scavenger receptor, and thereafter the inflammasome is activated. Thereafter, various chemokines/cytokines play their roles to eventually form fibrosis. Additionally, silica particles chronically activate T helper cells which sets the background for the formation of silicosis-associated autoimmune disturbances. The occurrence and progression of lung fibrosis, the extracellular matrix-related molecules such as integrins and their ligands including fibronectin, vitronectin, laminin, and collagens, all play important roles. Here, the roles of these molecules in silicosis-related lung fibrosis are reviewed from the literature. Additionally, the measurement of serum nephronectin (Npnt), a new member of the integrin family of ligands, is discussed, together with investigations attempting to delineate the role of Npnt in silica-induced lung fibrosis. Serum Npnt was found to be higher in silicosis patients compared to healthy volunteers and seems to play a role in the progression of fibrosis with other cytokines. Therefore, serum Npnt levels may be employed as a suitable marker to monitor the progression of fibrosis in silicosis patients.

Study of lung toxicity in rats exposed to silica powder with different hard metal constituents

The objective of this study was to assess the lung toxicity induced by the inhalation of different hard metal constituents and silica powder and screen for potential toxicity biomarkers. Rats were randomly divided into saline, cobalt, tungsten carbide, silica, and hard metal (HM) groups and were administered a single 10-mg dose of the respective treatments. After 8 weeks, the lung tissue structure in the HM group was deformed, numerous nucleated giant and epithelial-like cells appeared in the stroma, and the computed tomography scanning images appeared abnormal. Krebs von den Lungen-6 (KL-6), transforming growth factor (TGF)-β1, and TGF-β2 expression in bronchoalveolar lavage fluid (BALF) significantly differed between the groups ( p < 0.05). Serum KL-6 and TGF-β1, but not TGF-β2, levels significantly differed between some groups ( p < 0.05). We observed multinucleated giant cells in the rat lung tissue. While the serum and BALF levels of KL-6 and TGF-β2 are not highly specific, TGF-β1 may be a valuable reference diagnostic marker in HM lung disease.

Impact of Ultraviolet Radiation on Expression of Transforming Growth Factor β, Smad2, Metalloproteinases-1, -3, -8, -9, Cathepsin K and Progerin

Ultraviolet radiation (UVR) is one of the most important environmental factors involved in photoaging. Exposure to UVR leads to dysregulation of expression of cell cycle-related proteins which play key role in skin photodegradation that pretends to develop carcinogenesis. This study examines the role of various UVB doses on the expression of transforming growth factor beta (TGF-β), Smad2, cathepsin K, progerin and matrix metalloproteinases (MMPs)-1,-3,-8,-9. A group consisting of 63 healthy individuals underwent one of the following treatments: (1) whole body exposed to UVB irradiation on each of 10 consecutive days with 0.7 MED, or (2) whole-body irradiation as described followed by a single erythemal UVB dose on a small body area, or (3) irradiated only with a single erythemal UVB dose on small body area, or (4) were not irradiated at all (control group). When we compared all irradiated groups to the control group, there was significantly higher expression of TGF-β, MMP-1,-3,-9 and cathepsin K proteins evaluated by Western blot method. The results suggest the role of UVB in impairment of proteins expression that is involved in cell cycle's regulation. Changes in the protein expression involved by acute and chronic UVR confirm its essential role in skin photodestruction. Moreover, obtained result indicates the tendency to occurrence of photoadaptation phenomenon.

The Multifaceted Role of the Lysosomal Protease Cathepsins in Kidney Disease

Kidney disease is worldwide the 12th leading cause of death affecting 8–16% of the entire population. Kidney disease encompasses acute (short-lasting episode) and chronic (developing over years) pathologies both leading to renal failure. Since specific treatments for acute or chronic kidney disease are limited, more than 2 million people a year require dialysis or kidney transplantation. Several recent evidences identified lysosomal proteases cathepsins as key players in kidney pathophysiology. Cathepsins, originally found in the lysosomes, exert important functions also in the cytosol and nucleus of cells as well as in the extracellular space, thus participating in a wide range of physiological and pathological processes. Based on their catalytic active site residue, the 15 human cathepsins identified up to now are classified in three different families: serine (cathepsins A and G), aspartate (cathepsins D and E), or cysteine (cathepsins B, C, F, H, K, L, O, S, V, X, and W) proteases. Specifically in the kidney, cathepsins B, D, L and S have been shown to regulate extracellular matrix homeostasis, autophagy, apoptosis, glomerular permeability, endothelial function, and inflammation. Dysregulation of their expression/activity has been associated to the onset and progression of kidney disease. This review summarizes most of the recent findings that highlight the critical role of cathepsins in kidney disease development and progression. A better understanding of the signaling pathways governed by cathepsins in kidney physiopathology may yield novel selective biomarkers or therapeutic targets for developing specific treatments against kidney disease.

Therapeutic effects of bone marrow-derived mononuclear cells from healthy or silicotic donors on recipient silicosis mice

Background

Administration of bone marrow mononuclear cells (BMMCs) modulates lung inflammation and fibrosis in experimental silicosis. However, no studies have evaluated whether silicosis affects the efficacy of autologous BMMCs treatment. We hypothesized that BMMCs obtained from healthy or silicotic mice may improve lung function, but they might affect the inflammatory and fibrotic processes differently in experimental silicosis.

Methods

C57BL/6 mice were randomly divided into control (C) and silicosis (SIL) groups. Mice in the SIL group were instilled with silica particles intratracheally; the C animals received saline using the same protocol. On day 15, the animals were treated with saline (Sal) or BMMCs (2 × 10⁶ cells) from healthy (BMMC-healthy) and silicotic (BMMC-sil) donors. Lung mechanics were measured, and lungs were collected for histology and molecular biology analysis.

Results

BMMCs obtained from healthy and silicotic donors presented similar percentages of cell populations. ^99mTc-BMMCs tracking revealed preferential migration of cells to the liver, and only a few GFP⁺ BMMCs were observed in lung tissue 24 h after treatment, regardless of donor type. Both the SIL-BMMC-healthy and SIL-BMMC-sil groups showed improvement in lung function, a reduction in the fractional area of granuloma, and a decrease in the number of mononuclear and apoptotic cells in lung parenchyma. In addition, the number of F4/80⁺ macrophages, the levels of interleukin-1 beta and transforming growth factor beta, and collagen fiber content in granuloma were reduced in SIL-BMMC-healthy mice, whereas mRNA expression of MMP-9 and procollagen I and III was reduced in the SIL-BMMC-sil group.

Conclusions

Administration of BMMCs from healthy and silicotic donors reduced lung inflammation and fibrosis, thus improving lung function. In addition, BMMC-healthy exhibited a greater improvement in lung morpho-functional changes in murine model of silicosis.

The interplay of matrix metalloproteinase-8, transforming growth factor-β1 and vascular endothelial growth factor-C cooperatively contributes to the aggressiveness of oral tongue squamous cell carcinoma

Background:

Matrix metalloproteinase-8 (MMP-8) has oncosuppressive properties in various cancers. We attempted to assess MMP-8 function in oral tongue squamous cell carcinoma (OTSCC).

Methods:

MMP-8 overexpressing OTSCC cells were used to study the effect of MMP-8 on proliferation, apoptosis, migration, invasion and gene and protein expression. Moreover, MMP-8 functions were assessed in the orthotopic mouse tongue cancer model and by immunohistochemistry in patient samples.

Results:

MMP-8 reduced the invasion and migration of OTSCC cells and decreased the expression of MMP-1, cathepsin-K and vascular endothelial growth factor-C (VEGF-C). VEGF-C was induced by transforming growth factor-β1 (TGF-β1) in control cells, but not in MMP-8 overexpressing cells. In human OTSCC samples, low MMP-8 in combination with high VEGF-C was an independent predictor of poor cancer-specific survival. TGF-β1 treatment also restored the migration of MMP-8 overexpressing cells to the level of control cells. In mouse tongue cancer, MMP-8 did not inhibit metastasis, possibly because it was eliminated in the peripheral carcinoma cells.

Conclusions:

The suppressive effects of MMP-8 in OTSCC may be mediated through interference of TGF-β1 and VEGF-C function and altered proteinase expression. Together, low MMP-8 and high VEGF-C expression have strong independent prognostic value in OTSCC.

Role of Proteases in Lung Disease: A Brief Overview

Proteases play an important role in health and disease of the lung. In the normal lungs, proteases maintain their homeostatic functions that regulate processes like its regeneration and repair. Dysregulation of proteases–antiproteases balance is crucial in the manifestation of different types of lung diseases. Chronic inflammatory lung pathologies are associated with a marked increase in protease activities. Thus, in addition to protease activities, inhibition of anti-proteolytic control mechanisms are also important for effective microbial infection and inflammation in the lung. Herein, we briefly summarize the role of different proteases and to some extent antiproteases in regulating a variety of lung diseases.

Development of a Novel Enzyme-Linked Immunosorbent Assay Targeting a Neo-Epitope Generated by Cathepsin-Mediated Turnover of Type III Collagen and Its Application in Chronic Obstructive Pulmonary Disease

A high level of extracellular matrix (ECM) turnover characterizes several lung diseases with fibrotic features. Type III collagen is one of the most abundant collagens in lung parenchyma, and cathepsins play a role in lung pathology, being responsible for tissue remodeling. In this study, we explore the diagnostic features of neo-epitope fragments of type III collagen generated by cathepsins that could reflect the pathological tissue turnover in patients with different diseases. A novel enzyme-linked immunosorbent assay (ELISA) measuring cathepsins B, L, S and K -generated type III collagen fragments (C3C) was developed for assessment in serum and plasma. The assay was biologically validated in serum from patients with chronic obstructive pulmonary disease (COPD). Serological levels of C3C were significantly elevated in patients with COPD compared to healthy controls (p = 0.0006). Levels of C3C in serum and heparin plasma of COPD patients had a highly significant correlation (R² = 0.86, p<0.0001). The data suggests that the C3C fragment is elevated in patients with COPD compared to healthy controls.

The Elusive Antifibrotic Macrophage

Fibrotic diseases, especially of the liver, the cardiovascular system, the kidneys, and the lungs, account for approximately 45% of deaths in Western societies. Fibrosis is a serious complication associated with aging and/or chronic inflammation or injury and cannot be treated effectively yet. It is characterized by excessive deposition of extracellular matrix (ECM) proteins by myofibroblasts and impaired degradation by macrophages. This ultimately destroys the normal structure of an organ, which leads to loss of function. Most efforts to develop drugs have focused on inhibiting ECM production by myofibroblasts and have not yielded many effective drugs yet. Another option is to stimulate the cells that are responsible for degradation and uptake of excess ECM, i.e., antifibrotic macrophages. However, macrophages are plastic cells that have many faces in fibrosis, including profibrotic behavior-stimulating ECM production. This can be dependent on their origin, as the different organs have tissue-resident macrophages with different origins and a various influx of incoming monocytes in steady-state conditions and during fibrosis. To be able to pharmacologically stimulate the right kind of behavior in fibrosis, a thorough characterization of antifibrotic macrophages is necessary, as well as an understanding of the signals they need to degrade ECM. In this review, we will summarize the current state of the art regarding the antifibrotic macrophage phenotype and the signals that stimulate its behavior.

In vitro cadmium effects on ECM gene expression in human bronchial epithelial cells

Occupational and environmental exposure to the heavy metal cadmium (Cd) and its inhalation from cigarette smoke are associated with emphysema. Many growth factors and extracellular matrix (ECM) cell signaling molecules are directly involved in the epithelial bronchial cell pathway. This study investigated the direct effects of Cd on the production of several ECM components in human bronchial epithelial cells (BEAS-2B) that were exposed in vitro for 48 h to sub-toxic and toxic concentrations of Cd. Gene expression of collagens, metalloproteases (MMPs), integrins, tenascin and vitronectin were quantified by RT-PCR. To study apoptosis cascade, annexin assay and cellular cytotoxicity by MTT assay were performed. We also investigated whether an imbalance in the TGFβ/TGFβ receptor (TGFβR) expression mediated Cd effects. The results showed the sub-toxic Cd dose significantly increased tenascin, vitronectin, β1 and β5 integrin gene expression. The toxic Cd dose decreased type IV and V collagen, α1, α2 and β3 integrins. Both Cd doses down-regulated type I collagen and up-regulated metalloproteases. Each Cd dose caused a different imbalance in the complex pattern of TGFβ and its receptors. No alteration in classic apoptotic marker protein expression was observed in presence of the sub-toxic dose of Cd, suggesting this metal alters ECM production without apoptotic activation. In conclusion, all these data show even sub-toxic Cd dose exposure alters the specific gene expression of several ECM components that are crucially implicated in the mechanical properties of lung parenchyma supporting the hypothesis that the mechanism underlying Cd-induced lung disease may involve downstream changes in TGFβ/TGFβR signaling.

Ultraviolet A-induced cathepsin K expression is mediated via MAPK/AP-1 pathway in human dermal fibroblasts

Background

Cathepsin K (CatK), a cysteine protease with the potent elastolytic activity, plays a predominant role in intracellular elastin degradation in human dermal fibroblasts (HDFs), and contributes to solar elastosis. In previous studies, CatK expression was downregulated in photoaged skin and fibroblasts, but upregulated in acute UVA-irradiated skin and fibroblasts. The underlying mechanisms regulating UVA-induced CatK expression remain elusive.

Objective

This study investigates mechanisms involved in the regulation of UVA-induced CatK expression in HDFs.

Methods

Primary HDFs were exposed to UVA. Cell proliferation was analyzed using a colorimetric assay of relative cell number. Quantitative real-time RT-PCR and Western blot were performed to detect CatK expression in HDFs on three consecutive days after 10 J/cm² UVA irradiation, or cells treated with increasing UVA doses. UVA-activated MAPK/AP-1 pathway was examined by Western blot. Effects of inhibition of MAPK pathway and knockdown of Jun and Fos on UVA-induced CatK expression were also measured by real-time RT-PCR and Western blot.

Results

UVA significantly increased CatK mRNA and protein expression in a dose-dependent manner. UVA-induced CatK expression occurred along with UVA-activated phosphorylation of JNK, p38 and Jun, UVA-increased expression of Fos. Inactivation of JNK and p38MAPK pathways both remarkably decreased UVA-induced CatK expression, which was suppressed more by inhibition of JNK pathway. Furthermore, knockdown of Jun and Fos significantly attenuated basal and UVA-induced CatK expression.

Conclusion

UVA is capable of increasing CatK expression in HDFs, most likely by activation of MAPK pathway and of AP-1, which has been shown to be the case for matrix metalloproteinases. As current strategies for selecting anti-photoaging agents focus on their ability to decrease MMPs' expression through inhibiting UV- activated MAPK pathway, future strategies should also consider their effect on CatK expression.

Regulation of TGF-β1-driven differentiation of human lung fibroblasts: emerging roles of cathepsin B and cystatin C

Lung matrix homeostasis partly depends on the fine regulation of proteolytic activities. We examined the expression of human cysteine cathepsins (Cats) and their relative contribution to TGF-β1-induced fibroblast differentiation into myofibroblasts. Assays were conducted using both primary fibroblasts obtained from patients with idiopathic pulmonary fibrosis and human lung CCD-19Lu fibroblasts. Pharmacological inhibition and genetic silencing of Cat B diminished α-smooth muscle actin expression, delayed fibroblast differentiation, and led to an accumulation of intracellular 50-kDa TGF-β1. Moreover, the addition of Cat B generated a 25-kDa mature form of TGF-β1 in Cat B siRNA-pretreated lysates. Inhibition of Cat B decreased Smad 2/3 phosphorylation but had no effect on p38 MAPK and JNK phosphorylation, indicating that Cat B mostly disturbs TGF-β1-driven canonical Smad signaling pathway. Although mRNA expression of cystatin C was stable, its secretion, which was inhibited by brefeldin A, increased during TGF-β1-induced differentiation of idiopathic pulmonary fibrosis and CCD-19Lu fibroblasts. In addition, cystatin C participated in the control of extracellular Cats, because its gene silencing restored their proteolytic activities. These data support the notion that Cat B participates in lung myofibrogenesis as suggested for stellate cells during liver fibrosis. Moreover, we propose that TGF-β1 promotes fibrosis by driving the effective cystatin C-dependent inhibition of extracellular matrix-degrading Cats.

Genome-wide transcriptional response during the development of bleomycin-induced pulmonary fibrosis in sprague-dawley rats

Pulmonary fibrosis is a common consequence of many lung diseases and a leading cause of morbidity and mortality. The molecular mechanisms underlying the development of pulmonary fibrosis remain poorly understood. One model used successfully to study pulmonary fibrosis over the past few decades is the bleomycin-induced pulmonary fibrosis model. We aimed to identify the genes associated with fibrogenesis using an Affymetrix GeneChip system in a bleomycin-induced rat model for pulmonary fibrosis. To confirm fibrosis development, several analyses were performed, including cellular evaluations using bronchoalveolar lavage fluid, measurement of lactate dehydrogenase activity, and histopathological examinations. Common aspects of pulmonary fibrosis such as prolonged inflammation, immune cell infiltration, emergence of fibroblasts, and deposition of extracellular matrix and connective tissue elements were observed. Global gene expression analysis revealed significantly altered expression of genes (≥ 1.5-fold, p < 0.05.) in a time-dependent manner during the development of pulmonary fibrosis. Our results are consistent with previous results of well-documented gene expression. Interestingly, the expression of triggering receptor expressed on myeloid cells 2 (Trem2) , secreted phosphoprotein 1 (Spp1) , and several proteases such as Tpsab1, Mcpt1, and Cma1 was considerably induced in the lung after bleomycin treatment, despite little evidence that they are involved in pulmonary fibrogenesis. These data will aid in our understanding of fibrogenic mechanisms and contribute to the identification of candidate biomarkers of fibrotic disease development.

Cathepsin K is present in invasive oral tongue squamous cell carcinoma in vivo and in vitro

Objectives

Cathepsin K, a lysosomal cysteine protease, is expressed in the tumor microenvironment (TME) of skin carcinoma, but nothing is known about cathepsin K in oral tongue squamous cell carcinoma (OTSCC). Our aim was to describe the expression of cathepsin K in invasive OTSCC in vitro and in a series of clinical cancer specimens.

Materials and Methods

OTSCC invasion in vitro was studied using invasive HSC-3 tongue carcinoma cells in 3D organotypic models. In total, 121 mobile tongue OTSCCs and 10 lymph node metastases were analyzed for cathepsin K expression. The association between cathepsin K expression and clinicopathological factors was evaluated.

Results

Cysteine protease inhibitor E64 and cathepsin K silencing significantly (p<0.0001) reduced HSC-3 cell invasion in the 3D models. Cathepsin K was expressed in a majority of carcinoma and metastatic cells, but the expression pattern in carcinoma cells did not correlate with clinical parameters. Instead, the weak expression of cathepsin K in the invasive TME front correlated with increased overall recurrence (p<0.05), and in early-stage tumors this pattern predicted both cancer recurrence and cancer-specific mortality (p<0.05 and p<0.005, respectively).

Conclusions

Cathepsin K is expressed in OTSCC tissue in both carcinoma and TME cells. Although the diminished activity and expression in aggressive tongue HSC-3 cells reduced 3D invasion in vitro, the amount of cathepsin K in carcinoma cells was not associated with the outcome of cancer patients. Instead, cathepsin K in the invasive TME front seems to have a protective role in the complex progression of tongue cancer.

The expression and activity of cathepsins D, H and K in asthmatic airways

Tumstatin is an anti-angiogenic collagen IV α3 fragment, levels of which are reduced in the airways of asthmatics. Its reduction may be due to the degradation by extracellular matrix (ECM) proteases. Cathepsins play a role in ECM remodelling, with cathepsin D, H and K (CTSD, CTSH and CTSK) being associated with lung diseases. CTSD modulates the NC1 domains of collagen molecules including tumstatin, while CTSH and CTSK are involved in ECM degradation. The role of these cathepsins in the regulation of tumstatin in the lung has not previously been examined. We demonstrated that CTSB, D, F, H, K, L and S mRNA was expressed in the airways. Quantification of immunohistochemistry showed that there is no difference in the global expression of CTSD, CTSH and CTSK between asthmatics and non-asthmatics. CTSD and CTSK, but not CTSH had the capacity to degrade tumstatin. No difference was observed in the activity of CTSD and H in bronchoalveolar lavage fluid of asthmatic and non-asthmatics, while CTSK was undetectable. This indicates that while CTSD possesses the potential to directly regulate tumstatin, and thus angiogenesis through this mechanism however, it is not likely to be involved in the dysregulation of tumstatin found in asthmatic airways.

Regular exercise training attenuates pulmonary inflammatory responses to inhaled alumina refinery dust in mice

Exposure to alumina dust has been recently associated with impaired lung mechanics and inflammation. We aimed at evaluating if moderate exercise training prevents these outcomes. Twenty-three female BALB/c mice (25-30g) were randomly divided in two main groups: control (C) and exercise (E), which were submitted, or not, to 15min of swimming, 5 days/week during 4 weeks. Then, the animals were exposed for 1h to either saline solution (CS or ES) or to a suspension of 8mg/m(3) of alumina dust (CA or EA). Twenty-four hours later pulmonary mechanics was determined by the end-inflation occlusion method. Left lungs were prepared for histology and right lungs for TGF-β determination. Static elastance increased after alumina dust exposure independently of swimming. In CA group the viscoelastic component of elastance, the viscoelastic/inhomogeneous pressure, the polymorphonuclear amount, the fraction area of alveolar collapse and TGF-β increased. Thus, exercise training may mitigate the pro-inflammatory response to inhaled aluminum refinery dust.

Hypoxia-induced mitogenic factor (HIMF/FIZZ1/RELMα) in chronic hypoxia- and antigen-mediated pulmonary vascular remodeling

Background

Both chronic hypoxia and allergic inflammation induce vascular remodeling in the lung, but only chronic hypoxia appears to cause PH. We investigate the nature of the vascular remodeling and the expression and role of hypoxia-induced mitogenic factor (HIMF/FIZZ1/RELMα) in explaining this differential response.

Methods

We induced pulmonary vascular remodeling through either chronic hypoxia or antigen sensitization and challenge. Mice were evaluated for markers of PH and pulmonary vascular remodeling throughout the lung vascular bed as well as HIMF expression and genomic analysis of whole lung.

Results

Chronic hypoxia increased both mean pulmonary artery pressure (mPAP) and right ventricular (RV) hypertrophy; these changes were associated with increased muscularization and thickening of small pulmonary vessels throughout the lung vascular bed. Allergic inflammation, by contrast, had minimal effect on mPAP and produced no RV hypertrophy. Only peribronchial vessels were significantly thickened, and vessels within the lung periphery did not become muscularized. Genomic analysis revealed that HIMF was the most consistently upregulated gene in the lungs following both chronic hypoxia and antigen challenge. HIMF was upregulated in the airway epithelial and inflammatory cells in both models, but only chronic hypoxia induced HIMF upregulation in vascular tissue.

Conclusions

The results show that pulmonary vascular remodeling in mice induced by chronic hypoxia or antigen challenge is associated with marked increases in HIMF expression. The lack of HIMF expression in the vasculature of the lung and no vascular remodeling in the peripheral resistance vessels of the lung is likely to account for the failure to develop PH in the allergic inflammation model.

Antifibrotic effects of curcumin are associated with overexpression of cathepsins K and L in bleomycin treated mice and human fibroblasts

Background

Lung fibrosis is characterized by fibroblast proliferation and the deposition of collagens. Curcumin, a polyphenol antioxidant from the spice tumeric, has been shown to effectively counteract fibroblast proliferation and reducing inflammation and fibrotic progression in animal models of bleomycin-induced lung injury. However, there is little mechanistic insight in the biological activity of curcumin. Here, we study the effects of curcumin on the expression and activity of cathepsins which have been implicated in the development of fibrotic lung diseases.

Methods

We investigated the effects of curcumin administration to bleomycin stimulated C57BL/6 mice and human fetal lung fibroblasts (HFL-1) on the expression of cathepsins K and L which have been implicated in matrix degradation, TGF-β1 modulation, and apoptosis. Lung tissues were evaluated for their contents of cathepsins K and L, collagen, and TGF-β1. HFL-1 cells were used to investigate the effects of curcumin and cathepsin inhibition on cell proliferation, migration, apoptosis, and the expression of cathepsins K and L and TGF-β1.

Results

Collagen deposition in lungs was decreased by 17-28% after curcumin treatment which was accompanied by increased expression levels of cathepsins L (25%-39%) and K (41%-76%) and a 30% decrease in TGF-β1 expression. Moreover, Tunel staining of lung tissue revealed a 33-41% increase in apoptotic cells after curcumin treatment. These in vivo data correlated well with data obtained from the human fibroblast line, HFL-1. Here, cathepsin K and L expression increased 190% and 240%, respectively, in the presence of curcumin and the expression of TGF-β1 decreased by 34%. Furthermore, curcumin significantly decreased cell proliferation and migration and increased the expression of surrogate markers of apoptosis. In contrast, these curcumin effects were partly reversed by a potent cathepsin inhibitor.

Conclusion

This study demonstrates that curcumin increases the expression of cathepsins K and L in lung which an effect on lung fibroblast cell behavior such as proliferation, migration and apoptosis rates and on the expression of TGF-β1 in mouse lung and HFL-1 cells. These results suggest that cathepsin-inducing drugs such as curcumin may be beneficial in the treatment of lung fibrosis.

Pulmonary fibroblasts mobilize the membrane-tethered matrix metalloprotease, MT1-MMP, to destructively remodel and invade interstitial type I collagen barriers

In acute and chronic lung disease, widespread disruption of tissue architecture underlies compromised pulmonary function. Pulmonary fibroblasts have been implicated as critical effectors of tissue-destructive extracellular matrix (ECM) remodeling by mobilizing a spectrum of proteolytic enzymes. Although efforts to date have focused on the catabolism of type I collagen, the predominant component of the lung interstitial matrix, the key collagenolytic enzymes employed by pulmonary fibroblasts remain unidentified. Herein, membrane type-1 matrix metalloprotease (MT1-MMP) is identified as the dominant and direct-acting protease responsible for the type I collagenolytic activity mediated by both mouse and human pulmonary fibroblasts. Furthermore, MT1-MMP is shown to be essential for pulmonary fibroblast migration within three-dimensional (3-D) hydrogels of cross-linked type I collagen that recapitulate ECM barriers encountered in the in vivo environment. Together, these findings demonstrate that MT1-MMP serves as a key effector of type I collagenolytic activity in pulmonary fibroblasts and earmark this pericellular collagenase as a potential target for therapeutic intervention.

Effect of mesoporous silica under Neisseria meningitidis transformation process: environmental effects under meningococci transformation

Background

This study aimed the use of mesoporous silica under the naturally transformable Neisseria meningitidis, an important pathogen implicated in the genetic horizontal transfer of DNA causing a escape of the principal vaccination measures worldwide by the capsular switching process. This study verified the effects of mesoporous silica under N. meningitidis transformation specifically under the capsular replacement.

Methods

we used three different mesoporous silica particles to verify their action in N. meningitis transformation frequency.

Results

we verified the increase in the capsular gene replacement of this bacterium with the three mesoporous silica nanoparticles.

Conclusion

the mesouporous silica particles were capable of increasing the capsule replacement frequency in N. meningitidis.

The effect of cathepsin K deficiency on airway development and TGF-β1 degradation

BACKGROUND

Cathepsin K, a cysteine protease predominantly expressed in osteoclasts, is a major drug target for the treatment of osteoporosis. Recent findings, however, indicate that cathepsin K is also involved in non-skeletal metabolism. The development of fibrotic phenotypes in lung and skin is a concern for cathepsin K inhibitors presently evaluated in clinical trials. Cathepsin K is expressed in lung tissue and has been implicated in lung fibrosis. However, little is known about the role of cathepsin K in airway development and its effect on TGF-β1 degradation.

METHODS

We investigated the effects of cathepsin K-deficiency on alterations in airway integrity, extracellular matrix composition, and TGF-β1 expression and degradation. Lung homogenates of wild-type and cathepsin K-deficient mice were used to evaluate their contents of collagen, glycosaminoglycans, and TGF-β1. The accessibility of TGF-β1 to cathepsin K-mediated degradation was determined in vitro and lung fibroblast proliferations in wild-type and cathepsin K-deficient cells were evaluated.

RESULTS

Lung airway cathepsin K expression in wild-type mice remained constant between 1 and 6 months of age and the airway integrity was maintained. In contrast, after 2 months of age, all Ctsk-/- mice demonstrated increased airway epithelium thickness by 16-28%, a lower structural airway integrity (1-2 score units lower), elevated cytokeratin expression of 12%, increased α-actin and vimentin expression by 50% and 70%, increased area of smooth muscle cells by 15%, elevated hydroxyproline and GAGs content by 20% and 25%, and increased TGF-β1 expression by 25%. TGF-β1 proved an efficient substrate of cathepsin K and TGF-β1 protein content in lung was increased by a potent cathepsin inhibitor. Lung fibroblasts from Ctsk-/- mice after TGF-β1 treatment showed increased proliferation rates, increased levels of TGF-β1 by 30%, and increased ECM secretion.

CONCLUSION

This study suggests that airway development is partly regulated by cathepsin K and that its expression contributes to the maintenance of the airway structural integrity. The anticipated use of therapeutic cathepsin K inhibitors needs to take potential changes in human lungs into consideration.

Morphea-like skin reactions in patients treated with the cathepsin K inhibitor balicatib

BACKGROUND

In a multicenter clinical trial in North America and Europe that tested the cathepsin K (catK) inhibitor balicatib for the treatment of osteoporosis, several patients developed hardening of the skin.

OBJECTIVE

We sought to characterize these observed adverse events.

METHODS

Patients with skin hardening were examined by a local dermatologist. All of those patients except one had at least one biopsy specimen taken from affected skin, which was read by local and two central dermatopathologists. Workup was directed for consideration of systemic scleroderma.

RESULTS

Nine patients of 709 treated with balicatib developed skin hardening and were given a diagnosis of morphea-like skin changes. No such events were observed in patients taking placebo or the lowest balicatib dose. After discontinuation of balicatib, skin changes resolved completely in 8 and partially in one patient.

LIMITATIONS

Each patient was seen by a different dermatologist in 6 different countries.

CONCLUSIONS

These observations are likely dose-related adverse effects of balicatib. Although catK was originally thought to be expressed only in osteoclasts, it has more recently also been found in lung and dermal fibroblasts and been implicated in the degradation of the extracellular matrix in the lung and the skin. It is therefore plausible that the observed dermal fibrosis in balicatib-treated patients is a result of impaired degradation of extracellular matrix proteins and may represent a class effect of catK inhibitors. We recommend that further exploration of catK inhibition for the treatment of osteoporosis or cancer should include monitoring for similar adverse effects.

Micro-computed tomography of pulmonary fibrosis in mice induced by adenoviral gene transfer of biologically active transforming growth factor-β1

Background

Micro-computed tomography (micro-CT) is a novel tool for monitoring acute and chronic disease states in small laboratory animals. Its value for assessing progressive lung fibrosis in mice has not been reported so far. Here we examined the importance of in vivo micro-CT as non-invasive tool to assess progression of pulmonary fibrosis in mice over time.

Methods

Pulmonary fibrosis was induced in mice by intratracheal delivery of an adenoviral gene vector encoding biologically active TGF-ß1 (AdTGF-ß1). Respiratory gated and ungated micro-CT scans were performed at 1, 2, 3, and 4 weeks post pulmonary adenoviral gene or control vector delivery, and were then correlated with respective histopathology-based Ashcroft scoring of pulmonary fibrosis in mice. Visual assessment of image quality and consolidation was performed by 3 observers and a semi-automated quantification algorithm was applied to quantify aerated pulmonary volume as an inverse surrogate marker for pulmonary fibrosis.

Results

We found a significant correlation between classical Ashcroft scoring and micro-CT assessment using both visual assessment and the semi-automated quantification algorithm. Pulmonary fibrosis could be clearly detected in micro-CT, image quality values were higher for respiratory gated exams, although differences were not significant. For assessment of fibrosis no significant difference between respiratory gated and ungated exams was observed.

Conclusions

Together, we show that micro-CT is a powerful tool to assess pulmonary fibrosis in mice, using both visual assessment and semi-automated quantification algorithms. These data may be important in view of pre-clinical pharmacologic interventions for the treatment of lung fibrosis in small laboratory animals.

Silica-induced TNF-alpha and TGF-beta1 expression in RAW264.7 cells are dependent on Src-ERK/AP-1 pathways

The cytokines secreted by lung macrophages have been shown to play a critical role in the pathogenesis of silicosis, tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta1 (TGF-beta1) are prominent cytokines in silicosis, but the underlying mechanism remains to be determined. The aim of the present study was to investigate the roles of Src-mitogen-activated protein kinase (MAPKs)/activator protein-1 (AP-1) signaling pathways in silica-induced TNF-alpha and TGF-beta1 expression in macrophage cells (RAW264.7). It was found that silica activated Src, p38 kinase, and extracellular signal-regulated kinase (ERK) in RAW264.7 cells. The induction of TNF-alpha and TGF-beta1 by silica was suppressed by Src inhibitor (PP1), ERK inhibitor (PD98059), but not by p38 kinase inhibitor (SB203580). Dominant negative mutant c-Jun (TAM67) inhibited silica-induced AP-1 DNA binding activity and downregulated the TNF-alpha and TGF-beta1 expression. In addition, PD98059 but not SB203580 inhibited the AP-1 DNA binding activity induced by silica. Based on these findings, it was conclude that Src-ERK/AP-1 signaling pathways are involved in the TNF-alpha and TGF-beta1 expression induced by silica in macrophages.

Time-response relationship of nano and micro particle induced lung inflammation. Quartz as reference compound

An increasing number of engineered particles, including nanoparticles, are being manufactured, increasing the need for simple low-dose toxicological screening methods. This study aimed to investigate the kinetics of biomarkers related to acute and sub-chronic particle-induced lung inflammation of quartz. Mice were intratracheal instilled with 50 µg of microsized or nanosized quartz. Acute inflammation was assessed 1, 2, 4, 8, 16 or 48 hours post exposure, whereas sub-chronic inflammation was investigated 3 months after exposure. Markers of acute inflammation in the bronchoalveolar lavage fluid (BALF) were neutrophils (PMN), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, macrophage inflammatory protein-2 (MIP-2), keratinocyte derived chemokine (KC) and total protein, which were all close to maximum 16 hours post instillation. No major differences were seen in the time-response profiles of nano- and micro-sized particles. The potency of the two samples cannot be compared; during the milling process, a substantial part of the quartz was converted to amorphous silica and contaminated with corundum. For screening, BALF PMN, either TNF-α or IL-1β at 16 hours post instillation may be useful. At 3 months post instillation, KC, PMN and macrophages were elevated. Histology showed no interstitial inflammation three months post instillation. For screening of sub-chronic effects, KC, PMN, macrophages and histopathology is considered sufficient.

Pulmonary toxicity of multi-walled carbon nanotubes (Baytubes) relative to alpha-quartz following a single 6h inhalation exposure of rats and a 3 months post-exposure period

Manufactured multi-walled carbon nanotubes (MWCNT) have attracted a great deal of attention due to their unique structural, chemical, and physical characteristics. This study utilized a 1x 6h inhalation exposure protocol followed by a 3 months post-exposure period. Wistar rats were nose-only exposed to 11 and 241 mg/m(3) MWCNT (Baytubes) of respirable, solid aerosol. MWCNT depleted of residual metals (depletion from 0.53% to 0.12% Co) were compared at 11 mg/m(3). Rats similarly exposed to air and alpha-quartz (248 mg/m(3)) served as negative and positive controls, respectively. Pulmonary response was characterized by bronchoalveolar lavage (BAL), lung histopathology, organ burden determinations, and gene expression analyses of lung homogenates with emphasis on extracellular matrix components. This acute inhalation exposure protocol was suitable to characterize and distinguish acute deposition-related effects from the long-term sequelae of retained MWCNT. Subtle differences in acute pulmonary toxic potency due to differences in metal contaminations could be revealed by this protocol. Consistent with the long retention halftime of poorly soluble particles, even short-term inhalation studies may require post-exposure periods of at least 3 months to reveal MWCNT-specific dispositional and toxicological characteristics relative to alpha-quartz. Distinct differences in the time course of pulmonary inflammation of MWCNT and alpha-quartz could be demonstrated. Transcriptomics proved to be a useful tool to analyze the etiopathology of collagen detected by BAL and histopathology. In summary, the pulmonary inflammogenicity following exposure to MWCNT was concentration-dependent with evidence of regression over time. Conversely, alpha-quartz resulted in progressive changes over time. The time course of pulmonary inflammation associated with retained MWCNT was independent on the concentration of residual cobalt. This supports the conclusion that the predominant response to inhaled MWCNT is principally related to the assemblage structure and not catalyst impurities (if in the range of < or = 0.5%).

Expression and regulation of cathepsin K in skin fibroblasts

Cathepsin K (catK) is a lysosomal cysteine protease with strong collagenolytic activity well known to mediate bone resorption in osteoclasts. Recently, catK has also been reported to be expressed in other tissues. In the dermis, it is expressed only under certain circumstances such as scarring or inflammation. We therefore investigated the expression and regulation of this protease in dermal fibroblasts using immunoblotting and immunostaining. Cultured skin fibroblasts were found to strongly express catK in lysosomes. Internalization of collagen I and IV to lysosomes of fibroblasts indicates a role of catK in intracellular collagen degradation after endocytosis, a process that is different from the metalloproteinase-mediated collagen degradation in the extracellular space. In fibroblasts, interleukin-1alpha and cellular confluence upregulate catK expression and transforming growth factor-beta1 inhibits confluence-induced catK upregulation in skin fibroblasts. RANKL (ligand of receptor activator of NF-kappaB) did not alter catK expression. These regulators of catK expression are likely to play a role in the as-needed upregulation in certain skin conditions, where the prominent matrix-degrading properties of catK are thought to require tight regulation to maintain the homeostasis of the extracellular matrix.

Modulation of cytokine production and silica-induced lung fibrosis by inhibitors of aminopeptidase N and of dipeptidyl peptidase-IV-related proteases

AIMS

Dipeptidyl peptidase IV (DP IV)-related proteases and aminopeptidase N (APN) are drug targets in various diseases. Here we investigated for the first time the effects of DP-IV-related protease inhibitors and APN inhibitors on chronic inflammatory lung diseases.

MAIN METHODS

A murine model of silica (SiO2)-induced lung fibrosis and in vitro cultures of human lung epithelial cells and monocytes have been used and the influence of silica-treatment and inhibitors on inflammation and fibrosis has been measured.

KEY FINDINGS

We found increased inflammation and secretion of the chemokines IL-6, MCP-1 and MIP-alpha 2 weeks after SiO2 application, and increased lung fibrosis after 3 months. Treatment with the APN inhibitor actinonin reduced chemokine secretion in the lung and bronchoalveolar lavage fluid, and in cell culture, and decreased the level of fibrosis after 3 months. Treatment with inhibitors of DP-IV-related proteases, or a combination of DP IV inhibitors and APN inhibitors, had no significant effect. We found no obvious side effects of long-term treatment with inhibitors of APN and DP IV.

SIGNIFICANCE

Overall, our findings show that actinonin, an inhibitor of aminopeptidase N, might modulate chemokine secretion in the lung and thus attenuate the development of lung fibrosis. Additional targeting of DP-IV-related proteases had no significant effect on these processes.

Nuclear cathepsin F regulates activation markers in rat hepatic stellate cells

Activation of hepatic stellate cells during liver fibrosis is a major event facilitating an increase in extracellular matrix deposition. The up-regulation of smooth muscle alpha-actin and collagen type I is indicative of the activation process. The involvement of cysteine cathepsins, a class of lysosomal cysteine proteases, has not been studied in conjunction with the activation process of hepatic stellate cells. Here we report a nuclear cysteine protease activity partially attributed to cathepsin F, which co-localizes with nuclear speckles. This activity can be regulated by treatment with retinol/palmitic acid, known to reduce the hepatic stellate cell activation. The treatment for 48 h leads to a decrease in activity, which is coupled to an increase in cystatin B and C transcripts. Cystatin B knockdown experiments during the same treatment confirm the regulation of the nuclear activity by cystatin B. We demonstrate further that the inhibition of the nuclear activity by E-64d, a cysteine protease inhibitor, results in a differential regulation of smooth muscle alpha-actin and collagen type I transcripts. On the other hand, cathepsin F small interfering RNA transfection leads to a decrease in nuclear activity and a transcriptional down-regulation of both activation markers. These findings indicate a possible link between nuclear cathepsin F activity and the transcriptional regulation of hepatic stellate cell activation markers.

Increased carcinogenic potential of myeloid tumor cells induced by aberrant TGF-beta1-signaling and upregulation of cathepsin B

The TGF-beta signaling pathways are implicated in cancer. Cysteine cathepsins can contribute to the carcinogenic potential of tumor cells. The aim of this study was to investigate the regulation of cysteine cathepsin expression by TGF-beta1 and the functional implications in tumor cells. We found an upregulation of cathepsin B (CathB, 2- to 5-fold) in different myeloid tumor cells (THP-1, MonoMac-1, MonoMac-6) after incubation with TGF-beta1. No upregulation was found in monocytes, and there was suppression of CathB expression in epithelial tumor cells (A549). Increased cathepsin B activity led to enhanced carcinogenic potential, which was reflected by increased migration and invasion of the cells and resistance to inhibitor-induced apoptosis. Analysis of the TGF-beta signaling pathways showed no alterations in TGF-beta/BMP receptor expression or SMAD2/3 phosphorylation, and no influence of MAP kinase pathways. However, a reduction in SMAD1 expression was detected. The lack of BMP action on cysteine cathepsin expression in myeloid tumor cells, but not in epithelial tumor cells, suggests a defect in the Smad1/Smad5 pathway. We located a related TGF-beta1-responsive element within the first intron of the CathB gene. In conclusion, alterations in the TGF-beta1 signaling pathway lead to upregulation of CathB, which contributes to the carcinogenic potential of tumor cells.