Osteopontin is a multifunctional matricellular protein abundantly expressed during inflammation and repair. Osteopontin deficiency is associated with abnormal wound repair characterized by aberrant collagen fibrillogenesis in the heart and skin. Recent gene microarray studies found that osteopontin is abundantly expressed in both human and mouse lung fibrosis. Macrophages and T cells are known to be major sources of osteopontin. During lung fibrosis, however, osteopontin expression continues to increase when inflammation has receded, suggesting alternative sources of ostepontin during this response. In this study, we demonstrate immunoreactivity for osteopontin in lung epithelial and inflammatory cells in human usual interstitial pneumonitis and murine bleomycin-induced lung fibrosis. After treatment with bleomycin, osteopontin-null mice develop lung fibrosis characterized by dilated distal air spaces and reduced type I collagen expression compared with wild-type controls. There is also a significant decrease in levels of active transforming growth factor-beta(1) and matrix metalloproteinase-2 in osteopontin null mice. Type III collagen expression and total collagenase activity are similar in both groups. These results demonstrate that osteopontin expression is associated with important fibrogenic signals in the lung and that the epithelium may be an important source of osteopontin during lung fibrosis.

. NF-B induced by IL-1␤ inhibits elastin transcription and myofibroblast phenotype. Am J Physiol Cell Physiol 283: C58-C65, 2002; 10.1152/ ajpcell.00314.2001.-Interleukin (IL)-1␤ released after lung injury regulates the production of extracellular matrix components. We found that IL-1␤ treatment reduced the rate of elastin gene transcription by 74% in neonatal rat lung fibroblasts. Deletion analysis of the rat elastin promoter detected a cis-acting element located at Ϫ118 to Ϫ102 bp that strongly bound Sp1 and Sp3 but not nuclear factor (NF)-B. This element mediated IL-1␤-induced inhibition of the elastin promoter. IL-1␤ treatment did not affect the level of Sp1 but did induce translocation of the p65 subunit of NF-B. Overexpression of p65 decreased elastin promoter activity and markedly reduced elastin mRNA. Immunoprecipitation studies indicated an interaction between the p65 subunit and Sp1 protein. Microarray analysis of mRNA isolated after overexpression of p65 or treatment with IL-1␤ revealed downregulation of ␣-smooth muscle actin and calponin mRNAs. Expression of these genes is associated with the myofibroblast phenotype. These results indicate that IL-1␤ activates the nuclear localization of NF-B that subsequently interacts with Sp1 to downregulate elastin transcription and expression of the myofibroblast phenotype. nuclear factor-B; interleukin-1␤; Sp1 ELASTIN IS a major structural protein in the lung. It is found most notably in alveolar walls and blood vessels. Tropoelastin, a soluble precursor, is synthesized in alveolar structures by interstitial fibroblasts and in vascular tissue by smooth muscle cells (4,34,35). Elastin synthesis in the pulmonary parenchyma of the rodent lung is highest during alveolarization. This process usually begins in the postnatal period and decreases with maturity (4, 25). Disruption of elastin deposition during development results in failure of alveolar formation (19). In the adult lung parenchyma, elastin mRNA is minimally expressed in interstitial structures but can be reactivated during the development of pulmonary emphysema or fibrosis (18,20).We previously reported (20) that elastin and collagen mRNA levels are upregulated after bleomycin treatment of rodent lungs. This expression was confined primarily to myofibroblasts. The myofibroblast phenotype is characterized by ␣-smooth muscle actin expression (28). Myofibroblasts appear to be responsible for matrix deposition during wound healing (31). In the adult lung, elastin mRNA levels can be modulated by effector substances released from macrophages or resident interstitial cells or from the extracellular matrix after proteolytic injury. Elastin mRNA can be upregulated by insulin-like growth factor, transforming growth factor (TGF)-␤, and retinoic acid (13,16,22) and downregulated by basic fibroblast growth factor (7) and interleukin (IL)-1␤ (3).IL-1␤ affects gene transcription via several different families of trans-acting factors including AP-1 proteins, nuclear factor (NF)/IL-6-related factors [CCAAT box/enhancer b...

Transforming growth factor-beta (TGF-beta) stimulates alpha(1)(I) collagen mRNA synthesis in human lung fibroblasts through a mechanism that is partially sensitive to cycloheximide and that may involve synthesis of connective tissue growth factor (CTGF). Northern blot analyses indicate that TGF-beta stimulates time- and dose-dependent increases in CTGF mRNA. In TGF-beta-stimulated fibroblasts, maximal levels of CTGF mRNA (3.7-fold above baseline) occur at 6 h. The TGF-beta-stimulated increase in CTGF mRNA was not blocked by cycloheximide. Nuclear run-on analysis indicates that TGF-beta increases the CTGF transcription rate. The TGF-beta-stimulated increases in CTGF transcription and steady-state levels of CTGF mRNA are attenuated in prostaglandin E(2) (PGE(2))-treated fibroblasts. PGE(2) fails to attenuate luciferase activity induced by TGF-beta in fibroblasts transfected with the TGF-beta-responsive luciferase reporter construct p3TP-LUX. In amino acid-deprived fibroblasts, PGE(2) and insulin regulate alpha(1)(I) collagen mRNA levels without affecting CTGF mRNA levels. The data suggest that the regulation of alpha(1)(I) collagen mRNA levels by TGF-beta and PGE(2) may function through both CTGF-dependent and CTGF-independent mechanisms.