Therapies for bleomycin induced lung fibrosis through regulation of TGF-Β1 induced collagen gene expression

This review describes normal and abnormal wound healing, the latter characterized by excessive fibrosis and scarring, which for lung can result in morbidity and sometimes mortality. The cells, the extracellular matrix (ECM) proteins, and the growth factors regulating the synthesis, degradation, and deposition of the ECM proteins will be discussed. Therapeutics with particular emphasis given to gene therapies and their effects on specific signaling pathways are described. Bleomycin (BM), a potent antineoplastic antibiotic increases TGF-Β1 transcription, TGF-Β1 gene expression, and TGF-Β protein. Like TGF-Β1, BM acts through the same distal promoter cis -element of the COL1A1 gene causing increased COL1 synthesis and lung fibrosis. Lung fibroblasts exist as subpopulations with one subset predominately responding to fibrogenic stimuli which could be a specific cell therapeutic target for the onset and development of pulmonary fibrosis. J. Cell. Physiol. 211: 585–589, 2007. © 2007 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55994/1/20972_ftp.pd

All-trans-Retinoic Acid Inhibition of Proα1(I) Collagen Gene Expression in Fetal Rat Skin Fibroblasts: Identification of a Retinoic Acid Response Element in the Proα1(I) Collagen Gene

The current study was undertaken to determine the mechanism by which the retinoid all-trans-retinoic acid regulates proα1(I) collagen gene expression in fetal rat skin fibroblasts. FRS fibroblasts were stably transfected with the ColCat3.6 plasmid, which contains a portion of the 5′ flanking region of the rat proα1(I) collagen gene linked to a reporter gene, chloramphenicol acetyltransferase. The effect of t-RA on CAT activity was determined as a function of concentration and incubation time. Maximal inhibition of CAT activity by t-RA occurred at 10−8 M after 48h of treatment. Transforming growth factor-β1; did not block the inhibitory effect of t-RA on CAT activity. Computer sequence analysis of the 3.6-kb DNA fragment that contains the promoter for the rat proα1(I) collagen gene identified a direct repeat RARE sequence composed of one diverse (5′-AG-TAGA-3′) and one idealized (5′-GGGTCA-3′) half site located at positions −1345 and −1335, respectively. Two nuclear retinoid receptors that were expressed in bacteria, retinoic acid receptor-γ and retinoid X receptor-α, were found to bind specifically to a double-stranded oligonucleotide containing the RARE in gel mobility shift assays. Mutation of the idealized half-site eliminated the binding of receptor proteins to the oligonucleotide. Gel mobility shift assays using nuclear protein extracts prepared from t-RA-treated FRS fibroblasts showed that binding to the oligonucleotide containing the RARE was decreased from control values. The same assays performed with the mutated oligonucleotide resulted in only slight bindbig. These studies indicate that t-RA downregulates the promoter activity of the rat proα1(I) collagen gene by decreasing the binding of nuclear protein to the RARE sequence in the 5′ flanking region of the gene