Idiopathic pulmonary fibrosis (IPF) is a progressive chronic disorder characterized by activation of fibroblasts and overproduction of extracellular matrix (ECM). Caveolin-1 (cav-1), a principal component of caveolae, has been implicated in the regulation of numerous signaling pathways and biological processes. We observed marked reduction of cav-1 expression in lung tissues and in primary pulmonary fibroblasts from IPF patients compared with controls. We also demonstrated that cav-1 markedly ameliorated bleomycin (BLM)-induced pulmonary fibrosis, as indicated by histological analysis, hydroxyproline content, and immunoblot analysis. Additionally, transforming growth factor β1 (TGF-β1), the well-known profibrotic cytokine, decreased cav-1 expression in human pulmonary fibroblasts. cav-1 was able to suppress TGF-β1–induced ECM production in cultured fibroblasts through the regulation of the c-Jun N-terminal kinase (JNK) pathway. Interestingly, highly activated JNK was detected in IPF- and BLM-instilled lung tissue samples, which was dramatically suppressed by ad–cav-1 infection. Moreover, JNK1-null fibroblasts showed reduced smad signaling cascades, mimicking the effects of cav-1. This study indicates a pivotal role for cav-1 in ECM regulation and suggests a novel therapeutic target for patients with pulmonary fibrosis.

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Interstitial lung fibrosis can develop as a consequence of occupational or medical exposure, as a result of genetic defects, and after trauma or acute lung injury leading to fibroproliferative acute respiratory distress syndrome, or it can develop in an idiopathic manner. The pathogenesis of each form of lung fibrosis remains poorly understood. They each result in a progressive loss of lung function with increasing dyspnea, and most forms ultimately result in mortality. To better understand the pathogenesis of lung fibrotic disorders, multiple animal models have been developed. This review summarizes the common and emerging models of lung fibrosis to highlight their usefulness in understanding the cell-cell and soluble mediator interactions that drive fibrotic responses. Recent advances have allowed for the development of models to study targeted injuries of Type II alveolar epithelial cells, fibroblastic autonomous effects, and targeted genetic defects. Repetitive dosing in some models has more closely mimicked the pathology of human fibrotic lung disease. We also have a much better understanding of the fact that the aged lung has increased susceptibility to fibrosis. Each of the models reviewed in this report offers a powerful tool for studying some aspect of fibrotic lung disease.Keywords: fibrosis; collagen; fibroblast; aging; cytokines Interstitial lung disease is often associated with the development of chronic fibrosis. These diseases are characterized clinically by progressive dyspnea, cough, restrictive physiology, and impaired gas exchange. Humans manifest many types of fibrotic lung disease (1). Among the diffuse parenchymal lung disorders (DPLDs) are diseases of known cause (e.g., drug-related, environmental exposures, or those associated with collagen vascular disease), the idiopathic interstitial pneumonias (IIPs), the granulomatous DPLDs (e.g., sarcoidosis), and rare noncategorized diseases, such as lymphangioleiomyomatosis. Idiopathic pulmonary fibrosis (IPF) is the most common disease within the category of IIPs, and is histopathologically identified as usual interstitial pneumonia (UIP). Additional diseases within the IIP category include desquamative interstitial pneumonia, respiratory bronchiolitis interstitial lung disease, acute interstitial pneumonia, cryptogenic organizing pneumonia, lymphocytic interstitial pneumonia, and nonspecific interstitial pneumonia (NSIP). IPF carries a poor prognosis, with a mean survival time of less than 5 years after diagnosis (2-5). Biopsies from a single patient can show heterogenous patterns consistent with both UIP and NSIP (4, 6, 7), suggesting that NSIP shares common pathogenic mechanisms with UIP.Diagnoses of patients with IPF who do not exhibit classic high-resolution computed tomography scan changes are confirmed by histopathologic evaluations of surgical lung biopsies, which demonstrate the pattern of UIP. Hallmark features of UIP include epithelial cell hyperplasia, basement membrane denudation, alveolar consolidation, and fibroblastic foci in a pa...

The intracellular lalization of human copper,zinc superoxide dismutase (Cu,Zn-SOD; superoxide:superoxide oxidoreductase, EC 1.15.1.1) was evaluated by using EM immunocytochemistry and both Isolated human cell lines and human tissues. Eight monoclonal antibodies raised against either native or recombinant human Cu,Zn-SOD and two polyclonal antibodies raised against either native or recombinant human Cu,Zn-SOD were used. Fixation with 2% paraformaldehyde/0.2% glutaraldehyde was found necessary to preserve normal distribution of the protein. Monoclonal antibodies were less effective than polydonal antibodies in recognizing the antigen after adequate fixation oftissue. Cu,Zn-SOD was found widely distributed in the cell cytosol and in the cell nucleus, consistent with it being a soluble cytosolic protein.Mitochondria and secretory compartments did not label for this protein. In human cells, peroxisomes showed a labeling density slightly less than that of cytoplasm.The superoxide dismutases (SODs; superoxide:superoxide oxidoreductase, EC 1.15.1.1) are a family of enzymes commonly characterized by the metals that they contain and by their function to dismute 2-, thus providing essential protection of biological tissues against uncontrolled reactions with oxygen-based radicals. The copper,zinc form of SOD (Cu,Zn-SOD) is a dimer having a molecular mass of 32,000 Da. It has been identified as a soluble enzyme widely distributed in the cytoplasm of all mammalian cells (1). Previous EM immunocytochemical localization of this protein has been done on rat liver hepatocytes. The enzyme was found to be excluded from many membrane-bound compartments, such as nuclear envelope, endoplasmic reticulum, Golgi elements, secretory vesicles, and mitochondria (2). Quantitative immunocytochemistry done on rat Cu,Zn-SOD identified it to be widely distributed throughout the cytoplasm and nucleus; the cytoplasmic matrix had a concentration of 1.36 mg/ml, a concentration --50%o higher than that of the nuclear matrix (3). Lysosomes contained the highest concentration (5.81 mg/ml). Rat hepatocyte peroxisomes were found to contain the Cu,Zn-SOD in relatively low concentrations (0.27 mg/ml) (3).Keller et al. (4) recently evaluated the intracellular localization of Cu,Zn-SOD in human fibroblasts and hepatoma cells with four monoclonal antibodies (mAbs) raised against recombinant human (rh) Cu,Zn-SOD. Immunolocalization was done by using immunofluorescence (4, 5). The enzyme was reported to be localized only in punctate regions of the cells that were identified as peroxisomes because of colocalization of catalase to the same sites with a dual-immunofluorescence method. These authors speculated that the use of mAbs raised against a recombinant protein insured the reliability of their studies localizing SOD only to peroxisomes. MATERIALS AND METHODS mAbs. Four mAbs raised against rh Cu,Zn-SOD were obtained from Robert A. Hallewell (Chiron) and were designated CZSOD F2, CZSOD A3, CZSOD A6, and CZSOD A7, as reported by Keller et al. (4). A mAb ...

Idiopathic pulmonary fibrosis (IPF) is a severely debilitating disease associated with a dismal prognosis. There are currently no effective therapies for IPF, thus the identification of novel therapeutic targets is greatly needed. The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin superfamily of cell surface receptors whose activation has been linked to various pathologies. In healthy adult animals, RAGE is expressed at the highest levels in the lung compared to other tissues. To investigate the hypothesis that RAGE is involved in IPF pathogenesis, we have examined its expression in two mouse models of pulmonary fibrosis and in human tissue from IPF patients. In each instance we observed a depletion of membrane RAGE and its soluble (decoy) isoform, sRAGE, in fibrotic lungs. In contrast to other diseases in which RAGE signaling promotes pathology, immunohistochemical and hydroxyproline quantification studies on aged RAGEnull mice indicate that these mice spontaneously develop pulmonary fibrosis-like alterations. Furthermore, when subjected to a model of pulmonary fibrosis, RAGE-null mice developed more severe fibrosis, as measured by hydroxyproline assay and histological scoring, than wild-type controls. Combined with data from other studies on mouse models of pulmonary fibrosis and human IPF tissues indicate that loss of RAGE contributes to IPF pathogenesis. Idiopathic pulmonary fibrosis (IPF) is a debilitating disease with a dismal prognosis. Mean survival time after biopsy-confirmed diagnosis is 3 to 5 years.1,2 Traditional therapy involves the use of corticosteroids as nonspecific anti-inflammatory agents. This treatment produces an objective response in only 10 to 20% of patients and has a minimal effect on the fatal course of IPF.2-4 Thus, the need for new therapeutic modalities is evident.The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin super family of cell surface receptors. 5 In most healthy adult animal tissues, RAGE is expressed at low to undetectable levels.6,7 Activation of membrane-bound RAGE (mRAGE) by its ligands (including advanced glycation end products, HMGB1/amphoterin, S100/calgranulins, and amyloid-␤ peptide) often leads to proinflammatory signaling as well as up-regulation of RAGE itself.8 This signaling by mRAGE is believed to play an important role in disease progression for several nonpulmonary diseases, including various diabetic complications, chronic inflammation, and Alzheimer's disease, among others. 9,10 In contrast to other healthy adult tissues, RAGE mRNA and sRAGE protein are highly expressed in normal adult lungs. 6,7,11 Most recently it has been suggested that RAGE is a marker of type I alveolar epithelial cells 12 and type II alveolar epithelial cell transdifferentiation, a component of pulmonary re-epithelialization and repair.

The median survival of patients with idiopathic pulmonary fibrosis (IPF) continues to be approximately 3 years from the time of diagnosis, underscoring the lack of effective medical therapies for this disease. In the United States alone, approximately 40,000 patients die of this disease annually. In November 2012, the NHLBI held a workshop aimed at coordinating research efforts and accelerating the development of IPF therapies. Basic, translational, and clinical researchers gathered with representatives from the NHLBI, patient advocacy groups, pharmaceutical companies, and the U.S. Food and Drug Administration to review the current state of IPF research and identify priority areas, opportunities for collaborations, and directions for future research. The workshop was organized into groups that were tasked with assessing and making recommendations to promote progress in one of the following six critical areas of research: (1) biology of alveolar epithelial injury and aberrant repair; (2) role of extracellular matrix; (3) preclinical modeling; (4) role of inflammation and immunity; (5) genetic, epigenetic, and environmental determinants; (6) translation of discoveries into diagnostics and therapeutics. The workshop recommendations provide a basis for directing future research and strategic planning by scientific, professional, and patient communities and the NHLBI.

Reactive oxygen species, including superoxide, generally are considered neurotoxic molecules whose effects can be alleviated by antioxidants. Different from this view, we show that scavenging of superoxide with an antioxidant enzyme is associated with deficits in hippocampal long-term potentiation (LTP), a putative neural substrate of memory, and hippocampal-mediated memory function. Using transgenic mice that overexpress extracellular superoxide dismutase (EC-SOD), a superoxide scavenger, we found that LTP was impaired in hippocampal area CA1 despite normal LTP in area CA3. The LTP impairment in area CA1 could be reversed by inhibition of EC-SOD. In addition, we found that EC-SOD transgenic mice exhibited impaired long-term memory of fear conditioning to contextual cues despite exhibiting normal short-term memory of the conditioning experience. These findings strongly suggest that superoxide, rather than being considered exclusively a neurotoxic molecule, should also be considered a signaling molecule necessary for normal neuronal function.

SUMMARY The receptor for advanced glycation endproducts (RAGE) is a pro-inflammatory pattern recognition receptor (PRR) that has been implicated in the pathogenesis of numerous inflammatory diseases. It was discovered in 1992 on endothelial cells and was named for its ability to bind advanced glycation endproducts and promote vascular inflammation in the vessels of patients with diabetes. Further studies revealed that RAGE is most highly expressed in lung tissue and spurred numerous explorations into RAGE’s role in the lung. These studies have found that RAGE is an important mediator in allergic airway inflammation (AAI) and asthma, pulmonary fibrosis, lung cancer, chronic obstructive pulmonary disease (COPD), acute lung injury, pneumonia, cystic fibrosis, and bronchopulmonary dysplasia. RAGE has not yet been targeted in the lungs of paediatric or adult clinical populations, but the development of new ways to inhibit RAGE is setting the stage for the emergence of novel therapeutic agents for patients suffering from these pulmonary conditions.