Cell-specific elevation of NRF2 and sulfiredoxin-1 as markers of oxidative stress in the lungs of idiopathic pulmonary fibrosis and non-specific interstitial pneumonia.

Human idiopathic pulmonary fibrosis (IPF) and non-specific interstitial pneumonia (NSIP) have been proposed to be attributable to oxidative stress. The nuclear factor, erythroid derived 2, like protein (NRF2)-sulfiredoxin-1 (SRX1) pathway was hypothesized to be associated with the pathogenesis of human pulmonary fibrosis. Several methods including digital morphometry were used in the assessment of the cell-specific localization and expression of NRF2 and SRX1 and selected proteins linked to their activation/stability in human IPF/usual interstitial pneumonia (UIP) and NSIP lung. The proteins of the NRF2 pathway were localized in the hyperplastic alveolar epithelium and inflammatory cells in IPF and NSIP, but were absent in the fibroblastic foci characteristic of IPF. Morphometric evaluation revealed NRF2 and KEAP1 to be significantly elevated in the hyperplastic alveolar epithelium compared with the normal alveolar epithelium, and NRF2 was remarkably expressed in the nuclear compartment of the hyperplastic cells. SRX1 was expressed mainly in alveolar macrophages, and the number of SRX1-positive macrophages/surface area was elevated in NSIP, a disease which contains more marked inflammatory reaction compared with the IPF/UIP lung. The expression of the NRF2 pathway in human IPF and NSIP is further evidence that the pathogenesis of human fibrotic lung diseases is oxidant-mediated and originates from the alveolar epithelium.

Homing peptides as targeted delivery vehicles.

Each normal organ and pathological condition appear to contain organ- or disease-specific molecular tags on its vasculature, which constitute a vascular "zip code" system. In vivo phage display has been exploited to profile this vascular heterogeneity and a number of peptides that home specifically to various normal organs or pathological conditions have been identified. These peptides have been used for targeted delivery of oligonucleotides, drugs, imaging agents, inorganic nanoparticles, liposomes, and viruses. Identification of the receptor molecules for the homing peptides has revealed novel biomarkers for target organs. In tumors many of these receptors seem to play a functional role in tumor angiogenesis. Recently, tumor homing peptides have entered clinical trials. Results from several Phase I and II trials have been reported, and a number of trials are currently ongoing or recruiting patients. In these trials no dose-limiting toxicity has occurred and all combinations of peptide-targeted therapies have been well tolerated.

Peroxiredoxin II expression and its association with oxidative stress and cell proliferation in human idiopathic pulmonary fibrosis.

Oxidant burden has been suggested to be a contributor to the pathogenesis of idiopathic pulmonary fibrosis (IPF). The study focused on peroxiredoxin (Prx) II, an antioxidant that has been associated with platelet-derived growth factor (PDGF) signaling and consequent cell proliferation. Localization and expression of Prx II, PDGF receptors (PDGFRalpha, PDGFRbeta), Ki67, and nitrotyrosine were assessed in control (n=10) and IPF/usual interstitial pneumonia (UIP) (n=10) lung biopsies by immunohistochemistry and morphometry. Prx II oxidation was determined by standard and non-reducing Western blots, two-dimensional gel electrophoresis, and mass spectrometry. Prx II localized in the IPF/UIP epithelium and alveolar macrophages. Prx II-positive area in the fibroblastic foci (FF) was smaller than in other parenchymal areas (p=0.03) or in the hyperplastic epithelium (p=0.01). There was no major Prx II oxidation in IPF/UIP compared with the normal lung. The FF showed only minor immunoreactivity to the PDGFRs; Ki67, a marker of cell proliferation; and nitrotyrosine, a marker of oxidative/nitrosative stress. The results suggest that Prx II oxidation does not relate to the pathogenesis of IPF/UIP and that Prx II, PDGFRs, and proliferating cells colocalize in the IPF/UIP lung. Unexpectedly, FF represented areas of low cell proliferation.

Imatinib mesylate inhibits fibrogenesis in asbestos-induced interstitial pneumonia.

Profibrogeneic cytokines contribute to the accumulation of myofibroblasts in the lung interstitium in idiopathic pulmonary fibrosis (IPF). Imatinib mesylate, a tyrosine kinase inhibitor specific for Abl, platelet-derived growth factor receptor (PDGFR) and c-Kit tyrosine kinases, has been shown to inhibit fibrosis and profibrotic signaling in mouse models of inflammation-mediated lung reactions. The authors tested imatinib mesylate in vivo in a mouse model of crocidolite asbestos-induced progressive fibrosis. The ability of imatinib mesylate to inhibit profibrogeneic cytokine-induced human pulmonary fibroblast migration was tested in vitro and the expression of its target protein tyrosine kinases was assessed with immunofluorescence. In vivo, 10 mg/kg/day imatinib mesylate inhibited histological parenchymal fibrosis and led to a decrease in collagen deposition, but had no significant effect on asbestos-induced neutrophilia. However, 50 mg/kg/day imatinib mesylate did not inhibit collagen deposition. In vitro, IPF fibroblasts expressed Abl, PDGFR-alpha, PDGF-beta, but not c-Kit, and 1 microM imatinib mesylate inhibited profibrogeneic cytokine-induced IPF fibroblast migration. These results suggest that imatinib mesylate is a potential and specific inhibitor of fibroblast accumulation in asbestos-induced pulmonary fibrosis.

Elevated matrilysin levels in bronchoalveolar lavage fluid do not distinguish idiopathic pulmonary fibrosis from other interstitial lung diseases.

Microarray studies have shown that matrilysin or matrix metalloproteinase (MMP)-7 is highly upregulated in the lungs of patients with idiopathic pulmonary fibrosis (IPF), but MMP-7 protein expression has not been systematically compared between IPF and other interstitial lung diseases. MMP-7 levels in bronchoalveolar lavage fluid (BALF) were compared to corresponding samples from nonspecific interstitial pneumonia (NSIP), sarcoidosis, and healthy controls. MMP-7 levels in the BALF were determined by ELISA and localization of MMP-7 in the lung tissue by immunohistochemistry. MMP-7 was similarly elevated in the BALF of all these disorders compared to healthy controls (p=0.007). Even control subjects with prolonged cough displayed a tendency towards elevated MMP-7 expression. There was a negative correlation between BALF MMP-7 levels and forced expiratory vital capacity (r=-0.348, p=0.02, n=42). In IPF lung, MMP-7 immunoreactivity appeared predominantly in the fibrotic parenchyma and arterial wall. In sarcoidosis and NSIP, prominent MMP-7 immunoreactivity was found in areas of inflammation. These results demonstrate that elevated BALF MMP-7 is not restricted to IPF alone but is also observed in other interstitial lung diseases and cannot be used as a differential diagnostic marker for IPF.

Bone morphogenetic protein-4 inhibitor gremlin is overexpressed in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF), ie, usual interstitial pneumonia in histopathology, is a disease characterized by tissue destruction and active areas of fibroproliferation in the lung. Gremlin (Drm), a member of the cysteine knot family of bone morphogenetic protein (BMP) inhibitors, functions to antagonize BMP-4-mediated signals during lung development. We describe here consistent overexpression of gremlin in the lung interstitium of IPF patients. Quantitative real-time reverse transcriptase-polymerase chain reaction analyses revealed considerably higher levels of gremlin mRNA in lung biopsies from IPF patients, the highest level being 35-fold higher compared to controls. Lung fibroblasts isolated from IPF patients also expressed elevated levels of gremlin, which was associated with impaired responsiveness to endogenous and exogenous BMP-4. Transforming growth factor-beta-induced epithelial-to-mesenchymal transition of A549 lung epithelial cells in culture was also associated with induction of gremlin mRNA expression. In addition, A549 cells transfected to overexpress gremlin were more susceptible to transforming growth factor-beta-induced epithelial-to-mesenchymal transition. Gremlin-mediated inhibition of BMP-4 signaling pathways is likely to enhance the fibrotic response and reduce epithelial regeneration in the lung. The overexpression of this developmental gene in IPF may be a key event in the persistence of myofibroblasts in the lung interstitium and provides a potential target for therapeutic intervention.

Structural and functional analysis of integrin alpha2I domain interaction with echovirus 1.

Integrins are cell surface receptors for several microbial pathogens including echovirus 1 (EV1), a picornavirus. Cryo-electron microscopy revealed that the functional domain (alpha(2)I) of human alpha(2)beta(1) integrin binds to a surface depression on the EV1 capsid. This three-dimensional structure of EV1 bound to alpha(2)I domain provides the first structural details of an integrin interacting with a picornavirus. The model indicates that alpha(2)beta(1) integrin cannot simultaneously bind both EV1 and the physiological ligand collagen. Compared with collagen binding to the alpha(2)I domain, the virus binds with a 10-fold higher affinity but in vitro uncoating of EV1 was not observed as a result of attachment of alpha(2)I. A molecular model, constructed on the basis of the EV1-integrin complex, shows that multiple alpha(2)beta(1) heterodimers can bind at adjacent sites around the virus 5-fold symmetry axes without steric hindrance. In agreement with this, virus attachment to alpha(2)beta(1) integrin on the cell surface was found to result in integrin clustering, which can give rise to signaling and facilitate the initiation of the viral entry process that takes place via caveolae-mediated endocytosis.