NF-κB induced by IL-1β inhibits elastin transcription and myofibroblast phenotype

Abstract

. 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...

Tumor Necrosis Factor-α Inhibits Endothelial Nitric-oxide Synthase Gene Promoter Activity in Bovine Aortic Endothelial Cells

“…Alternatively, NFB could reduce Sp1 binding to DNA through protein-protein interactions that don't directly involve DNA contact points. Interaction of p65 and Sp1 have been demonstrated in co-immunoprecipitation studies previously (72). If this is the correct mechanism, it would imply selectivity for certain Sp1-binding elements, because Sp1 binding to the downstream element was unaffected by TNF-␣ treatment.…”

Regression of Abdominal Aortic Aneurysms by Simultaneous Inhibition of Nuclear Factor κB and Ets in a Rabbit Model

“…Activation of NFB induced by interleukin-1␤ decreased elastin promoter activity and elastin mRNA level. 10 NFB may also affect elastin synthesis indirectly through decreased tumor necrosis factor ␣ expression. Tumor necrosis factor ␣ is regulated by NFB and has been found to markedly suppress the elastin mRNA level and transcriptional activity of the elastin gene in cultured human skin fibroblasts and rat aortic vascular smooth muscle cells.…”

“…[7][8][9] Furthermore, recent studies have demonstrated that NFB inhibits transcription of the elastin and collagen genes, leading to suppression of their synthesis. 10,11 In contrast, members of the ets family, including MMP-1, MMP-2, and MMP-9, also play important roles in regulating gene expression in response to multiple developmental and mitogenic signals. [12][13][14] From this viewpoint, we used chimeric decoy oligodeoxynucleotides (ODNs) to inhibit both NFB and ets simultaneously, leading to the inhibition of a wide variety of MMPs, including MMP-1, MMP-2, MMP-3, and MMP-9, which play a pivotal role in human AAA.…”

Positive transcriptional regulatory element located within exon 1 of elastin gene

“…Other positive-acting ELN promoter elements directly bind transactivating factors, such as the nuclear factor-1 binding site at approximately Ϫ400 of the ELN gene (5). Functional elements that repress elastin expression on exposure to basic fibroblast growth factor (bFGF) (2,3,27), interleukin (IL)-1␤ (14,15), and tumor necrosis factor-␣ (TNF-␣) (11) have been defined. Studies in transgenic mice reported tissue-specific activity of a transgene containing 5.2 kb of 5Ј-flanking sequence, although comparisons between expression patterns of the transgene and the endogenous gene were not made (9,13,17,26).…”