PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-7 (7)
 

Clipboard (0)
None

Select a Filter Below

Journals
Year of Publication
Document Types
1.  Asbestos-Induced Alveolar Epithelial Cell Apoptosis. The Role of Endoplasmic Reticulum Stress Response 
Asbestos exposure results in pulmonary fibrosis (asbestosis) and malignancies (bronchogenic lung cancer and mesothelioma) by mechanisms that are not fully understood. Alveolar epithelial cell (AEC) apoptosis is important in the development of pulmonary fibrosis after exposure to an array of toxins, including asbestos. An endoplasmic reticulum (ER) stress response and mitochondria-regulated (intrinsic) apoptosis occur in AECs of patients with idiopathic pulmonary fibrosis, a disease with similarities to asbestosis. Asbestos induces AEC intrinsic apoptosis, but the role of the ER is unclear. The objective of this study was to determine whether asbestos causes an AEC ER stress response that promotes apoptosis. Using human A549 and rat primary isolated alveolar type II cells, amosite asbestos fibers increased AEC mRNA and protein expression of ER stress proteins involved in the unfolded protein response, such as inositol-requiring kinase (IRE) 1 and X-box–binding protein-1, as well as ER Ca²2+ release ,as assessed by a FURA-2 assay. Eukarion-134, a superoxide dismutase/catalase mimetic, as well as overexpression of Bcl-XL in A549 cells each attenuate asbestos-induced AEC ER stress (IRE-1 and X-box–binding protein-1 protein expression; ER Ca²2+ release) and apoptosis. Thapsigargin, a known ER stress inducer, augments AEC apoptosis, and eukarion-134 or Bcl-XL overexpression are protective. Finally, 4-phenylbutyric acid, a chemical chaperone that attenuates ER stress, blocks asbestos- and thapsigargin-induced AEC IRE-1 protein expression, but does not reduce ER Ca²2+ release or apoptosis. These results show that asbestos triggers an AEC ER stress response and subsequent intrinsic apoptosis that is mediated in part by ER Ca²2+ release.
doi:10.1165/rcmb.2013-0053OC
PMCID: PMC3931115  PMID: 23885834
alveolar epithelium; asbestos; mitochondria; endoplasmic reticulum; apoptosis
2.  Fat in Fibrosis 
doi:10.1164/rccm.201305-0971LE
PMCID: PMC3863733  PMID: 24236597
3.  Cyclic stretch-induced nuclear localization of transcription factors results in increased nuclear targeting of plasmids in alveolar epithelial cells 
The journal of gene medicine  2008;10(6):668-678.
Background
We have shown previously that cyclic stretch corresponding to that experienced by the pulmonary epithelium during normal breathing enhances nonviral gene transfer and expression in alveolar epithelial cells by increasing plasmid intracellular trafficking. Although reorganization of the microtubule and actin cytoskeletons by cyclic stretch is necessary for increased plasmid trafficking, the role of nuclear entry in this enhanced trafficking has not been elucidated.
Methods
Alveolar epithelial cells were subjected to biaxial cyclic stretch (10% change in surface area at 0.5 Hz) and assayed for RNA expression, nuclear localization and activation of key transcription factors. Stretched epithelial cells were transfected with plasmids via electroporation and exposed to inhibitors of transcription factor activation.
Results
When assayed by in situ hybridization, more plasmids were localized to the nuclei of cells that were stretched following electroporation compared to unstretched cells. Cyclic stretch also increases the nuclear localization of multiple transcription factors thought to be involved in plasmid nuclear entry, including AP1, AP2, NF-κB and NF1. Specific inhibition of the nuclear import of AP1 and/or NF-κB abolishes the enhanced plasmid nuclear localization seen with stretch.
Conclusions
Nuclear entry of plasmids is thought to be mediated by the binding of proteins that chaperone the DNA through the nuclear pore. Stretch-enhanced nuclear localization of transcription factors increases nuclear targeting of plasmids, whereas inhibition of the nuclear import of specific transcription factors abrogated stretch-enhanced plasmid nuclear localization. Taken together, these results suggest that cyclic stretch increases gene trafficking in the cytoplasm and at the nuclear envelope.
doi:10.1002/jgm.1187
PMCID: PMC4084625  PMID: 18361478
cyclic stretch; gene therapy; electroporation; plasmid; trafficking; transcription factors
4.  Nuclear β-Catenin Is Increased in Systemic Sclerosis Pulmonary Fibrosis and Promotes Lung Fibroblast Migration and Proliferation 
Pulmonary fibrosis is a disease that results in loss of normal lung architecture, but the signaling events that drive tissue destruction are incompletely understood. Wnt/β-catenin signaling is important in normal lung development, but whether abnormal signaling occurs in lung fibrosis due to systemic sclerosis and the consequences of β-catenin signaling toward the fibrogenic phenotype remain poorly defined. In this study, we show nuclear β-catenin accumulation in fibroblastic foci from lungs of patients with systemic sclerosis–associated advanced pulmonary fibrosis. Forced activation of β-catenin signaling in three independently derived sources of normal human lung fibroblasts promotes proliferation and migratory activities but is not sufficient to activate classic markers of fibroblast activation, such as TGF-β, type 1 collagen, α-smooth muscle actin, and connective tissue growth factor. These findings indicate that activation of β-catenin signaling in pulmonary fibroblasts may be a common feature of lung fibrosis, contributing to fibroproliferative and migratory activities associated with the disease.
doi:10.1165/rcmb.2010-0113OC
PMCID: PMC3262680  PMID: 21454805
Wnt/β-catenin signaling; scleroderma; fibrosis
5.  β-catenin signaling: a novel mediator of fibrosis and potential therapeutic target 
Current Opinion in Rheumatology  2011;23(6):562-567.
Purpose of review
The Wnt/β-catenin signaling pathway plays a critical role in development and adult tissue homeostasis. Recent investigations implicate Wnt/β-catenin signaling in abnormal wound repair and fibrogenesis. The purpose of this review is to highlight recent key studies that support a role for Wnt/β-catenin signaling in fibrosis.
Recent findings
Studies of patients with fibrotic diseases have demonstrated changes in components of the Wnt/β-catenin pathway. In animal models, perturbations in Wnt/β-catenin signaling appear to aggravate or ameliorate markers of injury and fibrosis in a variety of different tissues. Studies also suggest that fibroblasts from different tissue sources may have markedly divergent responses to Wnt/β-catenin signaling. Cross-talk between Wnt/β-catenin and transforming growth factor-β pathways is complex and context-dependent, and may promote fibrogenesis through coregulation of fibrogenic gene targets. High throughput screening has identified several novel chemical inhibitors of Wnt/β-catenin signaling that may be of therapeutic potential.
Summary
Wnt/β-catenin signaling appears important in normal wound healing and its sustained activation is associated with fibrogenesis. The mechanism by which Wnt/β-catenin signaling may modify the response to injury is cell-type and context-dependent. Better understanding of this signaling pathway may provide a promising new therapeutic approach for human fibrotic diseases.
doi:10.1097/BOR.0b013e32834b3309
PMCID: PMC3280691  PMID: 21885974
β-catenin; fibrosis; Wnt; wound repair
6.  Wnt/β-catenin signaling is hyperactivated in systemic sclerosis and induces Smad-dependent fibrotic responses in mesenchymal cells 
Arthritis and rheumatism  2012;64(8):2734-2745.
Introduction
Fibrosis in human diseases and animal models is associated with aberrant Wnt/β-catenin pathway activation. The regulation, activity, mechanism of action and significance of Wnt/β-catenin signaling in the context of systemic sclerosis (SSc) has not been characterized.
Methods
Expression of Wnt signaling pathway components in SSc skin biopsies was analyzed. The regulation of profibrotic responses by canonical Wnt/ß-catenin was examined in explanted human mesenchymal cells. Fibrotic responses were studied by proliferation, migration and gel contraction assays. The fate specification of subcutaneous preadipocytes by canonical Wnt signaling was evaluated.
Results
Analysis of published genome-wide expression datasets revealed elevated expression of the Wnt receptor Fzd2 and the Wnt target Lef1, and decreased expression of Wnt antagonists Dkk2 and Wif1 in skin biopsies from subsets of dcSSc patients. Immunohistochemistry showed increased nuclear β-catenin expression in these biopsies. In vitro, Wnt3a induced ß-catenin activation, stimulated fibroblast proliferation, migration, gel contraction and myofibroblast differentiation, and profibrotic gene expression. Genetic and pharmacological approaches were used to demonstrate that these profibrotic responses involved autocrine TGF-β signaling via Smads. In contrast, in explanted subcutaneous preadipocytes Wnt3a repressed adipogenesis and promoted myofibroblast differentiation.
Conclusions
Canonical Wnt signaling was hyperactivated in SSc skin biopsies, and in explanted mesenchymal cells Wnt3a stimulated fibrogenic responses while suppressing adipogenesis. Together, these results indicate that Wnts have potent profibrotic effects and canonical Wnt signaling plays an important role in the pathogenesis of fibrosis and lipoatrophy in SSc.
doi:10.1002/art.34424
PMCID: PMC3553791  PMID: 22328118
7.  Proteasomal inhibition after injury prevents fibrosis by modulating TGF-β1 signalling 
Thorax  2011;67(2):139-146.
Background
The development of organ fibrosis after injury requires activation of transforming growth factor β1 which regulates the transcription of profibrotic genes. The systemic administration of a proteasomal inhibitor has been reported to prevent the development of fibrosis in the liver, kidney and bone marrow. It is hypothesised that proteasomal inhibition would prevent lung and skin fibrosis after injury by inhibiting TGF-β1-mediated transcription.
Methods
Bortezomib, a small molecule proteasome inhibitor in widespread clinical use, was administered to mice beginning 7 days after the intratracheal or intradermal administration of bleomycin and lung and skin fibrosis was measured after 21 or 40 days, respectively. To examine the mechanism of this protection, bortezomib was administered to primary normal lung fibroblasts and primary lung and skin fibroblasts obtained from patients with idiopathic pulmonary fibrosis and scleroderma, respectively.
Results
Bortezomib promoted normal repair and prevented lung and skin fibrosis when administered beginning 7 days after the initiation of bleomycin. In primary human lung fibroblasts from normal individuals and patients with idiopathic pulmonary fibrosis and in skin fibroblasts from a patient with scleroderma, bortezomib inhibited TGF-β1-mediated target gene expression by inhibiting transcription induced by activated Smads. An increase in the abundance and activity of the nuclear hormone receptor PPARγ, a repressor of Smad-mediated transcription, contributed to this response.
Conclusions
Proteasomal inhibition prevents lung and skin fibrosis after injury in part by increasing the abundance and activity of PPARγ. Proteasomal inhibition may offer a novel therapeutic alternative in patients with dysregulated tissue repair and fibrosis.
doi:10.1136/thoraxjnl-2011-200717
PMCID: PMC3595535  PMID: 21921091

Results 1-7 (7)