JunD and HIF-1α mediate transcriptional activation of angiotensinogen by TGF-β1 in human lung fibroblasts

Earlier work showed that TGF-β1 potently increases angiotensinogen (AGT) gene mRNA in primary human lung fibroblasts. Here the mechanism of TGF-β1-induced AGT expression was studied in the IMR90 human lung fibroblast cell line. The increase in AGT mRNA induced by TGF-β1 was completely blocked by actinomycin-D. TGF-β1 increased the activity of a full-length human AGT promoter-luciferase reporter (AGT-LUC) but did not alter AGT mRNA half-life. Serial deletion analyses revealed that 67% of TGF-β-inducible AGT-LUC activity resides in a small domain of the AGT core promoter; this domain contains binding sites for hypoxia-inducible factor (HIF)-1 and activation protein-1 (AP-1) transcription factors. TGF-β1 increased HIF-1α protein abundance and the activity of a hypoxia-responsive element reporter; overexpression of HIF-1 increased basal AGT-LUC activity. Both oligonucleotide pulldown and chromatin immunoprecipitation assays revealed increased binding of JunD and HIF-1α to the AGT core promoter in response to TGF-β1. TGF-β1-inducible AGT-LUC was reduced by an AP-1 dominant negative or by mutation of the AP-1 site. Knockdown of either JunD or HIF-1α individually by siRNA partially reduced AGT-LUC. In contrast, simultaneous knockdown of both JunD and HIF-1α completely eliminated TGF-β1-inducible AGT-LUC activity. These data suggest that TGF-β1 up-regulates AGT transcription in human lung fibroblasts through a mechanism that requires both JunD and HIF-1α binding to the AGT core promoter. They also suggest a molecular mechanism linking hypoxia signaling and fibrogenic stimuli in the lungs.—Abdul-Hafez, A., Shu, R., Uhal, B. D. JunD and HIF-1α mediate transcriptional activation of angiotensinogen by TGF-β1 in human lung fibroblasts

Hematopoietic colony stimulating factors in cardiovascular and pulmonary remodeling: Promoters or inhibitors?

Hemopoietic colony stimulating factors (HCSFs) are naturally occurred substances that are released in response to infection or inflammation and regulate the proliferation and differentiation of hemopoietic progenitor cells. Some representative members of this peptide family induce atherogenesis through the mediation of monocyte-endothelial cell adhesive interaction and promotion of angiogenesis within the atherosclerotic plaques. HCSFs, such as granulocyte-macrophage colony-stimulating factor (GM-CSF), also promote post-infarction cardiac remodeling though the enhanced activation and infiltration of monocytes into injured myocardial tissue and through altered equilibrium of collagen deposition/degradation. On the other hand, exogenous administration of granulocyte colony-stimulating factor (G-CSF) or eythropoietin (EPO) in patients with chronic ischemic disease or recent myocardial infarction have lead to beneficial arteriogenesis or myocardial cell regeneration, thus preventing adverse cardiac remodeling. While GM-CSF may hold therapeutic potential as an inhibitor of lung fibrogenesis, G-CSF appears to promote fibrosis in the lungs. The pathophysiological role of HCSFs also depends on the timing of their action on cardiovascular remodeling, as well as on the target progenitor hematopoietic cell. This article summarizes current knowledge about the clinical and therapeutic implications of these factors in chronic artery disease, post-infarction cardiac remodeling, chronic heart failure and in pulmonary fibrosis. © 2006 Bentham Science Publishers Ltd

Cytopede: A Three-Dimensional Tool for Modeling Cell Motility on a Flat Surface

When cultured on flat surfaces, fibroblasts and many other cells spread to form thin lamellar sheets. Motion then occurs by extension of the sheet at the leading edge and retraction at the trailing edge. Comprehensive quantitative models of these phenomena have so far been lacking and to address this need, we have designed a three-dimensional code called Cytopede specialized for the simulation of the mechanical and signaling behavior of plated cells. Under assumptions by which the cytosol and the cytoskeleton are treated from a continuum mechanical perspective, Cytopede uses the finite element method to solve mass and momentum equations for each phase, and thus determine the time evolution of cellular models. We present the physical concepts that underlie Cytopede together with the algorithms used for their implementation. We then validate the approach by a computation of the spread of a viscous sessile droplet. Finally, to exemplify how Cytopede enables the testing of ideas about cell mechanics, we simulate a simple fibroblast model. We show how Cytopede allows computation, not only of basic characteristics of shape and velocity, but also of maps of cell thickness, cytoskeletal density, cytoskeletal flow, and substratum tractions that are readily compared with experimental data