Novel Genomic Effects of Glucocorticoids in Epidermal Keratinocytes

Abstract

Glucocorticoids (GCs) have a long history of use as therapeutic agents for numerous skin diseases. Surprisingly, their specific molecular effects are largely unknown. To characterize GC action in epidermis, we compared the transcriptional profiles of primary human keratinocytes untreated and treated with dexamethasone (DEX) for 1, 4, 24, 48, and 72 h using large scale microarray analyses. The majority of genes were found to be regulated only after 24 h and remained regulated throughout treatment. In addition to regulation of the expected pro-inflammatory genes, we found that GCs regulate cell fate, tissue remodeling, cell motility, differentiation, and metabolism. GCs suppress the expression of essentially all IFN␥-regulated genes, including IFN␥ receptor and STAT-1, an effect that was previously unknown. GCs also block STAT-1 activation and nuclear translocation. Unexpectedly, GCs induce the expression of anti-apoptotic genes and repress pro-apoptotic ones, preventing UVinduced keratinocyte apoptosis. Consequently, treatment with GCs blocked UV-induced apoptosis of keratinocytes. GCs have profound effect on wound healing by inhibiting cell motility and the expression of the proangiogenic factor, vascular endothelial growth factor. They play an important role in tissue remodeling and scar formation by suppressing the expression of TGF␤1 and -2 and MMP1, -2, -9, and -10 and inducing TIMP-2. Finally, GCs promote terminal epidermal differentiation while simultaneously inhibiting early stage differentiation. These results provide new insights into the beneficial and adverse effects of GCs in the epidermis, defining the participating genes and mechanisms that coordinate the cellular responses important for GC-based therapies.

Anti-inflammatory functions of glucocorticoid-induced genes

“…Expression of TTP mRNA was elevated by dex treatment of pulmonary epithelial A549 and BEAS-2B cells (Ishmael et al, 2007;Smoak and Cidlowski, 2006), primary human keratinocytes (Stojadinovic et al, 2006) or HeLa cells (our unpublished observations). GC-induced expression of TTP mRNA and protein in several rat tissues was confirmed by quantitative PCR and western blotting (Smoak and Cidlowski, 2006).…”

“…However, they fall short of proving that IκBα induction plays no part in the antiinflammatory actions of GCs. IκBα expression is tissue-specifically regulated, and is enhanced by GCs in several primary or transformed cell types (Almon et al, 2005;Auphan et al, 1995;Kang et al, 2006;Kurata and Yamamoto, 1999;Kurokouchi et al, 2000;Quan et al, 2000;Ramdas and Harmon, 1998;Scheinman et al, 1995a;Shames et al, 1998;Stojadinovic et al, 2006;Thiele et al, 1999). In A c c e p t e d M a n u s c r i p t A Clark Anti-inflammatory functions of glucocorticoid-induced genes Page 17 of 53 some cases GC treatment inhibited IκBα degradation, nuclear translocation of p65 or formation of nuclear NFκB complexes (Eberhardt et al, 2002;Goppelt-Struebe et al, 2000;Kurata and Yamamoto, 1999;Kurokouchi et al, 2000;Ma et al, 2004;Mukaida et al, 1994;Vital et al, 2003).…”

“…It is expressed in response to GCs A Clark Anti-inflammatory functions of glucocorticoid-induced genes Page 18 of 53 in a wide variety of cell types including mast cells (Kassel et al, 2001), monocytes or macrophages (Abraham et al, 2006;Aeberli et al, 2006;Bhattacharyya et al, 2007;Chen et al, 2002;Zhao et al, 2005), microglia (Zhou et al, 2007), T lymphocytes , dermal, lung and synovial fibroblasts (Phillips et al, 2006;Toh et al, 2004;Yang et al, 2006), endothelial cells (Furst et al, 2007), osteoblasts (Engelbrecht et al, 2003;Leclerc et al, 2004), keratinocytes (Onda et al, 2006;Stojadinovic et al, 2006), adipocytes (Bazuine et al, 2004), lung epithelial cells (Chivers et al, 2006;Hermoso et al, 2004), airway smooth muscle cells (Issa et al, 2007) and HeLa cells (Imasato et al, 2002;Lasa et al, 2002). Typically expression is quite rapid (within one hour), sustained (up to 24 hours), requires relatively low concentrations of GC, and is blocked by the GR antagonist RU486.…”

Astrocytes are a neural target of morphine action via glucocorticoid receptor‐dependent signaling

“…Members of this group include Tsc22d3 (GILZ, Stojadinovic et al, 2007;Ayroldi and Riccardi, 2009) Other genes may display an astrocyte-specific response to GCs. GR-dependent signaling relies on the cellular context (Leong et al, 2003;Yu et al, 2011), which may be associated with the recruitment of cell-type specific GR coactivators (Grenier et al, 2006).…”

Gene profiling: implications in dermatology

“…The primary targets of OsM regulation are secreted cytokines and growth factors and their receptors, as well as nuclear transcription factors. On the other hand, our studies focused on transcriptional profiling of anti-inflammatory agents, corticosteroids, revealed that in addition to known TNFa and IL-1 inhibitory effects, corticosteroids block activation of IFN-γ pathway (44). Furthermore, the anti-inflammatory effects of corticosteroids have timed responses: anti-TNFα is the earliest (first hour), followed by anti-IL1 (24 -48 hours) and anti-IFN-γ (72 hours).…”