Attenuation of lung fibrosis in mice with a clinically relevant inhibitor of glutathione-S-transferase π

Idiopathic pulmonary fibrosis (IPF) is a debilitating lung disease characterized by excessive collagen production and fibrogenesis. Apoptosis in lung epithelial cells is critical in IPF pathogenesis, as heightened loss of these cells promotes fibroblast activation and remodeling. Changes in glutathione redox status have been reported in IPF patients. S-glutathionylation, the conjugation of glutathione to reactive cysteines, is catalyzed in part by glutathione-S-transferase π (GSTP). To date, no published information exists linking GSTP and IPF to our knowledge. We hypothesized that GSTP mediates lung fibrogenesis in part through FAS S-glutathionylation, a critical event in epithelial cell apoptosis. Our results demonstrate that GSTP immunoreactivity is increased in the lungs of IPF patients, notably within type II epithelial cells. The FAS-GSTP interaction was also increased in IPF lungs. Bleomycin- and AdTGFβ-induced increases in collagen content, α-SMA, FAS S-glutathionylation, and total protein S-glutathionylation were strongly attenuated in Gstp(–/–) mice. Oropharyngeal administration of the GSTP inhibitor, TLK117, at a time when fibrosis was already apparent, attenuated bleomycin- and AdTGFβ-induced remodeling, α-SMA, caspase activation, FAS S-glutathionylation, and total protein S-glutathionylation. GSTP is an important driver of protein S-glutathionylation and lung fibrosis, and GSTP inhibition via the airways may be a novel therapeutic strategy for the treatment of IPF

Differential Requirement for c-Jun N-terminal Kinase 1 in Lung Inflammation and Host Defense

The c-Jun N-terminal kinase (JNK) - 1 pathway has been implicated in the cellular response to stress in many tissues and models. JNK1 is known to play a role in a variety of signaling cascades, including those involved in lung disease pathogenesis. Recently, a role for JNK1 signaling in immune cell function has emerged. The goal of the present study was to determine the role of JNK1 in host defense against both bacterial and viral pneumonia, as well as the impact of JNK1 signaling on IL-17 mediated immunity. Wild type (WT) and JNK1 −/− mice were challenged with Escherichia coli, Staphylococcus aureus, or Influenza A. In addition, WT and JNK1 −/− mice and epithelial cells were stimulated with IL-17A. The impact of JNK1 deletion on pathogen clearance, inflammation, and histopathology was assessed. JNK1 was required for clearance of E. coli, inflammatory cell recruitment, and cytokine production. Interestingly, JNK1 deletion had only a small impact on the host response to S. aureus. JNK1 −/− mice had decreased Influenza A burden in viral pneumonia, yet displayed worsened morbidity. Finally, JNK1 was required for IL-17A mediated induction of inflammatory cytokines and antimicrobial peptides both in epithelial cells and the lung. These data identify JNK1 as an important signaling molecule in host defense and demonstrate a pathogen specific role in disease. Manipulation of the JNK1 pathway may represent a novel therapeutic target in pneumonia

Modulation of Glutaredoxin-1 Expression in a Mouse Model of Allergic Airway Disease

Glutaredoxins (GRX) are antioxidant enzymes that preferentially catalyze the reduction of protein-glutathione mixed disulfides. The formation of mixed disulfides with GSH is known as S-glutathionylation, a post-translational modification that is emerging as an important mode of redox signaling. Since asthma is a disease that is associated with increased oxidative stress and altered antioxidant defenses, we investigated the expression of GRX in a murine model of allergic airway disease. Sensitization and challenge of C57BL/6 mice with ovalbumin resulted in increased expression of GRX1 mRNA, as well as increased amounts of GRX1 protein and total GRX activity in the lung. Because GRX1 expression is prominent in bronchial epithelium, we isolated primary epithelial cells from mouse trachea to investigate the presence of GRX. Primary tracheal epithelial cells were found to express both GRX1 and 2 mRNA and detectable GRX activity. Treatment with IFN-γ increased the expression of GRX1 and overall GRX activity, resulting in attenuation of protein S-glutathionylation. In contrast, TGF-β1 caused decreased GRX1 expression and overall GRX activity, leading to markedly enhanced protein S-glutathionylation. GRX1 joins the cadre of antioxidant defenses known to be modulated during allergic airway inflammation

Asbestos, Lung Cancers, and Mesotheliomas: From Molecular Approaches to Targeting Tumor Survival Pathways

Fifteen years have passed since we published findings in the AJRCMB demonstrating that induction of early response fos/jun proto-oncogenes in rodent tracheal and mesothelial cells correlates with fibrous geometry and pathogenicity of asbestos. Our study was the first to suggest that the aberrant induction of signaling responses by crocidolite asbestos and erionite, a fibrous zeolite mineral associated with the development of malignant mesotheliomas (MMs) in areas of Turkey, led to altered gene expression. New data questioned the widely held belief at that time that the carcinogenic effects of asbestos in the development of lung cancer and MM were due to genotoxic or mutagenic effects. Later studies by our group revealed that proto-oncogene expression and several of the signaling pathways activated by asbestos were redox dependent, explaining why antioxidants and antioxidant enzymes were elevated in lung and pleura after exposure to asbestos and how they alleviated many of the phenotypic and functional effects of asbestos in vitro or after inhalation. Since these original studies, our efforts have expanded to understand the interface between asbestos-induced redox-dependent signal transduction cascades, the relationship between these pathways and cell fate, and the role of asbestos and cell interactions in development of asbestos-associated diseases. Of considerable significance is the fact that the signal transduction pathways activated by asbestos are also important in survival and chemoresistance of MMs and lung cancers. An understanding of the pathogenic features of asbestos fibers and dysregulation of signaling pathways allows strategies for the prevention and therapy of asbestos-related diseases