The fibrotic phenotype induced by IGFBP-5 is regulated by MAPK activation and egr-1-dependent and -independent mechanisms

Early growth response transcription factors: key mediators of fibrosis and novel targets for anti-fibrotic therapy

Fibrosis is a deregulated and ultimately defective form of tissue repair that underlies a large number of chronic human diseases, as well as obesity and aging. The pathogenesis of fibrosis involves multiple cell types and extracellular signals, of which transforming growth factor-ß (TGF-ß) is pre-eminent. The prevalence of fibrosis is rising worldwide, and to date no agents has shown clinical efficacy in the attenuating or reversing the process. Recent studies implicate the immediate-early response transcription factor Egr-1 in the pathogenesis of fibrosis. Egr-1 couples acute changes in the cellular environment to sustained alterations in gene expression, and mediates a broad spectrum of biological responses to injury and stress. In contrast to other ligand-activated transcription factors such as NF-κB, c-jun and Smad2/3 that undergo post-translational modification such as phosphorylation and nuclear translocation, Egr-1 activity is regulated via its biosynthesis. Aberrant Egr-1 expression or activity is implicated in cancer, inflammation, atherosclerosis, and ischemic injury and recent studies now indicate an important role for Egr-1 in TGF-ß-dependent profibrotic responses. Fibrosis in various animal models and human diseases such as scleroderma (SSc) and idiopathic pulmonary fibrosis (IPF) is accompanied by aberrant Egr-1 expression. Moreover Egr-1 appears to be required for physiologic and pathological connective tissue remodeling, and Egr-1-null mice are protected from fibrosis. As a novel profibrotic mediator, Egr-1 thus appears to be a promising potential target for the development of anti-fibrotic therapies.

Expression of high-mobility groups box-1/receptor for advanced glycation end products/osteopontin/early growth response-1 pathway in proliferative vitreoretinal epiretinal membranes

PURPOSE

The high-mobility group box -1 (HMGB1)/receptor for advanced glycation end products (RAGE)/osteopontin (OPN)/early growth response-1 (Egr-1) pathway is involved in inflammation, angiogenesis, and fibrosis. We investigated the expression of the components of this pathway in proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR) epiretinal membranes.

METHODS

Nine active and 13 inactive membranes from patients with PDR and 21 membranes from patients with PVR were studied by immunohistochemistry.

RESULTS

In PDR membranes, vascular endothelial cells expressed HMGB1, RAGE, OPN, and Egr-1 in 21, 15, 20, and 16 membranes, respectively. Stromal cells expressed HMGB1, RAGE, OPN, and Egr-1 in 21, 20, 20, and 16 membranes, respectively. Significant correlations were detected between the number of blood vessels expressing the panendothelial cell marker CD34 and the number of blood vessels and stromal cells expressing HMGB1, RAGE, and OPN. The numbers of blood vessels and stromal cells expressing CD34, HMGB1, RAGE, and OPN and stromal cells expressing Egr-1 were significantly higher in active membranes than in inactive membranes. In PVR membranes, spindle-shaped myofibroblasts expressing α-smooth muscle actin coexpressed HMGB1, RAGE, OPN, and Egr-1.

CONCLUSIONS

The HMGB1/RAGE/OPN/Egr-1 pathway may be involved in inflammatory, angiogenic and fibrotic responses in proliferative vitreoretinal disorders.

Interstitial lung disease in connective tissue diseases: evolving concepts of pathogenesis and management

Interstitial lung disease (ILD) is a challenging clinical entity associated with multiple connective tissue diseases, and is a significant cause of morbidity and mortality. Effective therapies for connective tissue disease-associated interstitial lung disease (CTD-ILD) are still lacking. Multidisciplinary clinics dedicated to the early diagnosis and improved management of patients with CTD-ILD are now being established. There is rapid progress in understanding and identifying the effector cells, the proinflammatory and profibrotic mediators, and the pathways involved in the pathogenesis of CTD-ILD. Serum biomarkers may provide new insights as risk factors for pulmonary fibrosis and as measures of disease progression. Despite these recent advances, the management of patients with CTD-ILD remains suboptimal. Further studies are therefore urgently needed to better understand these conditions, and to develop effective therapeutic interventions.

Curcumin upregulates insulin-like growth factor binding protein-5 (IGFBP-5) and C/EBPalpha during oral cancer suppression

Curcumin is a common food ingredient derived from the plant Curcuma longa and is a potent drug against tumorigenesis. Both insulin-like growth factor binding protein-5 (IGFBP-5) and CCAAT/enhancer-binding protein alpha (C/EBPalpha) are suppressors of head and neck carcinogenesis. We identified curcumin as an inducer of IGFBP-5 expression in multiple types of oral keratinocytes; furthermore, curcumin induces IGFBP-5 promoter activity in SAS oral cancer cells. Promoter deletion mapping identified a region (nt -71 to nt -59 relative to the transcription start site) as containing a C/EBPalpha-binding element that is indispensable for curcumin-mediated IGFBP-5 upregulation. Chromatin immunoprecipitation assays revealed that in vivo binding of C/EBPalpha to this region was remarkably increased in the presence of curcumin. Curcumin increased nuclear C/EBPalpha expression and IGFBP-5 expression through p38 activation and this was abrogated by SB203580 treatment. Furthermore, MKK6 expression activated p38 and C/EBPalpha, increasing IGFBP-5 promoter activity and expression. Finally, curcumin-induced IGFBP-5 expression is associated with the suppression of xenograft tumorigenesis in mice due to oral cancer cells. We conclude that curcumin activates p38, which, in turn, activates the C/EBPalpha transactivator by interacting with binding elements in the IGFBP-5 promoter. The consequential upregulation of C/EBPalpha and IGFBP-5 by curcumin is crucial to the suppression of oral carcinogenesis.