Cytokine-induced MMP13 Expression in Human Chondrocytes Is Dependent on Activating Transcription Factor 3 (ATF3) Regulation

Abstract

Irreversible breakdown of cartilage extracellular matrix (ECM) by the collagenase matrix metalloproteinase 13 (MMP13) represents a key event in osteoarthritis (OA) progression. Although inflammation is most commonly associated with inflammatory joint diseases, it also occurs in OA and is thus relevant to the prevalent tissue destruction. Here, inflammation generates a cFOS AP-1 early response that indirectly affects MMP13 gene expression. To ascertain a more direct effect on prolonged MMP13 production we examined the potential molecular events occurring between the rapid, transient expression of cFOS and the subsequent MMP13 induction. Importantly, we show MMP13 mRNA expression is mirrored by nascent hnRNA transcription. Employing ChIP assays, cFOS recruitment to the MMP13 promoter occurs at an early stage prior to gene transcription and that recruitment of transcriptional initiation markers also correlated with MMP13 expression. Moreover, protein synthesis inhibition following early FOS expression resulted in a significant decrease in MMP13 expression thus indicating a role for different regulatory factors modulating expression of the gene. Subsequent mRNA transcriptome analyses highlighted several genes induced soon after FOS that could contribute to MMP13 expression. Specific small interfering RNA-mediated silencing highlighted that ATF3 was as highly selective for MMP13 as cFOS. Moreover, ATF3 expression was AP-1(cFOS/cJUN)-dependent and expression levels were maintained after the early transient cFOS response. Furthermore, ATF3 bound the proximal MMP13 AP-1 motif in stimulated chondrocytes at time points that no longer supported binding of FOS Consequently, these findings support roles for both cFOS (indirect) and ATF3 (direct) in effecting MMP13 transcription in human chondrocytes.

Phenotypic instability of chondrocytes in osteoarthritis: on a path to hypertrophy

“…185,186 In OA chondrocytes, MMP13 gene expression can be induced by mechanical stress and inflammatory cytokines and adipokines, which act via different signaling cascades, including MAPKs. 69 These pathways impact on a complex transcriptional network that involves the actions of transcription factors like RUNX2, 187 CEBP␤, 116,187,188 ELF3, 82 HIF-2␣, 97,98,149 CREB, 148 and ATF3, 189 among others. 69 The transactivation of MMP13 in articular chondrocytes is also subject to epigenetic modulation, as shown by the repression of LEF1-driven MMP13 gene expression by SIRT1 190 or the impact of the methylation status of the MMP13 promoter in OA cartilage on its CREB-148 and HIF-2␣-driven 149 transcriptional activation.…”

Collagenolytic matrix metalloproteinases antagonize proteinase-activated receptor-2 activation, providing insights into extracellular matrix turnover

“…5B,C). ATF3 is a transcription factor we recently identified as regulating MMP13 expression following cytokine stimulation (24). Secreted MMP-1 and MMP-13 were subsequently detected in the culture medium 48 hours post-stimulation ( Fig.…”

Dynamic chromatin accessibility landscape changes following interleukin-1 stimulation

“…MMP13 is highly regulated by inflammatory signalling, the inhibition of which is a proposed therapeutic strategy in OA, however the mechanism by which cytokines directly impact on its expression has proven to be somewhat elusive [43]. Proximal promoter AP-1 factor binding is critical for the accurate inflammatory induced expression of the gene and in part the binding of ATF3, however, NF-B is also critical for activating cytokine-induced MMP13 expression [44][45][46][47]. The data here suggests this could in part be via a novel RelA-bound intron 5 enhancer.…”