Inhibition of connective tissue growth factor/CCN2 expression in human dermal fibroblasts by interleukin‐1α and β

Abstract

Connective tissue growth factor (CTGF/CCN2) is a matricellular protein induced by transforming growth factor (TGF)-beta and intimately involved with tissue repair and overexpressed in various fibrotic conditions. We previously showed that keratinocytes in vitro downregulate TGF-beta-induced expression of CTGF in fibroblasts by an interleukin (IL)-1 alpha-dependent mechanism. Here, we investigated further the mechanisms of this downregulation by both IL-1alpha and beta. Human dermal fibroblasts and NIH 3T3 cells were treated with IL-1alpha or beta in presence or absence of TGF-beta1. IL-1 suppressed basal and TGF-beta-induced CTGF mRNA and protein expression. IL-1alpha and beta inhibited TGF-beta-stimulated CTGF promoter activity, and the activity of a synthetic minimal promoter containing Smad 3-binding CAGA elements. Furthermore, IL-1alpha and beta inhibited TGF-beta-stimulated Smad 3 phosphorylation, possibly linked to an observed increase in Smad 7 mRNA expression. In addition, RNA interference suggested that TGF-beta activated kinase1 (TAK1) is necessary for IL-1 inhibition of TGF-beta-stimulated CTGF expression. These results add to the understanding of how the expression of CTGF in human dermal fibroblasts is regulated, which in turn may have implications for the pathogenesis of fibrotic conditions involving the skin.

Interleukin-1-induced changes in the glioblastoma secretome suggest its role in tumor progression

“…IL-1-mediated suppression of CTGF may thus indicate that IL-1 can suppress TGFβ signaling in our secretome. In support of this, opposing effects of IL-1 on tenascin-C and CTGF (similar to ours) have been reported [58]. Thrombospondin 1 (THBS-1) is an adhesive glycoprotein that mediates cell-to-cell and cell-to-matrix interactions.…”

Runx2/Smad3 Complex Negatively Regulates TGF-β-Induced Connective Tissue Growth Factor gene Expression in Vascular Smooth Muscle Cells

“…Interleukin-1 and -1 inhibit TGF--stimulated Smad3 phosphorylation by increasing Smad7 expression and by TGF-activated kinase1 (TAK1) 45) . Interfering with Smad3, PPAR and its ligands suppress CTGF expression in response to TGF- 46,47) .…”

IL‐1α Counteract TGF‐β Regulated Genes and Pathways in Human Fibroblasts

“…CTGF is characteristically overexpressed in fibrotic diseases and stimulated by TGF‐β in dermal fibroblasts. We previously showed that IL‐1α counteract TGF‐β‐stimulated CTGF mRNA expression in fibroblasts [Nowinski et al, ]. In this study, using microarray, TGF‐β increased CTGF expression 15‐fold and IL‐1 inhibited this increase by 32% (q‐value = 0.06 for the latter).…”

“…One mechanism behind this may be keratinocyte‐mediated downregulation of TGF‐β in fibroblasts in a paracrine action [Le Poole and Boyce, ]. As another way to limit fibrosis, we previously identified IL‐1α secreted from keratinocytes as a mediator of CTGF mRNA and protein suppression in human dermal fibroblasts [Nowinski et al, ; Nowinski et al, ]. Since the skin has a unique reservoir of preformed IL‐1α in the epidermis, it is possible that this cytokine is an important player not only in the immune defense, but also to limit excessive scarring after injury [Murphy et al, ; Behm et al, ].…”

“…This kinase was first discovered in the context of TGF‐β signaling, but seems to function primarily as an essential component of the IL‐1 pathway [Lu et al, ]. In a TAK1 knock‐down experiment, we previously showed that this kinase, at least in part, mediates IL‐1 inhibition of TGF‐β stimulated CTGF suppression [Nowinski et al, ]. The mechanism behind this is likely an atypical phosphorylation of Smad 3 by TAK1, leading to inhibition of Smad3 [Benus et al, ].…”