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Durham University

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Ciechomska, M., O'Reilly, S., Przyborski, S., Oakley, F., Bogunia-Kubik, K. & van Laar, J.M. (2016). Histone demethylation and toll‐like receptor 8–dependent cross‐talk in monocytes promotes transdifferentiation of fibroblasts in systemic sclerosis via Fra‐2. Arthritis & Rheumatology 68(6): 1493-1504.

Author(s) from Durham

Abstract

Objectives: To investigate whether epigenetic changes can modulate monocytes to produce tissue-inhibitor of metalloproteinase-1 (TIMP-1) via Fra2 (AP-1 family member), a novel downstream mediator promoting fibrogenesis.

Methods: AP-1 transcription factors and TIMP-1 expression was measured in monocytes from systemic sclerosis (SSc) patients and healthy controls (HC). Involvement of Fra2 in the regulation of TIMP-1 following TLR8 agonist treatment was investigated using luciferase activity assay and ChIP analysis. Expression of TIMP-1 and Fra2 was determined in response to TLR8 treatment and different histone modifications including 3'deazaneplanocin (DZNep) and apicidin. HC fibroblasts were co-cultured with DZNep plus TLR8-treated HC monocytes.

Results: Upregulation of Fra2 was detected in bleomycin-challenged mice and SSc skin biopsies. Enhanced expression of Fra2 and TIMP-1 was correlated in SSc monocytes (p=0.021). The expression of Fra1 was significantly (p=0.037) reduced in SSc monocytes. Inhibiting AP-1 activity reduced TIMP-1 production in TLR8 stimulated HC and SSc monocytes. ChIP experiments revealed binding of Fra-2 to the TIMP-1 promoter. Combination of DZNep plus TLR8 enhanced Fra2 and TIMP-1 expression in HC monocytes, whereas TLR8 plus apicidin repressed Fra2 and TIMP-1 expression. Finally, DZNep plus TLR8-treated HC monocytes induced strong production of α-SMA in dermal fibroblasts, which was inhibited by TIMP-1 blocking antibody.

Conclusions: These data demonstrate a novel role of histone demethylation induced by DZNep on Fra2-mediated TIMP-1 production by monocytes in the presence of TLR8 agonist. This consequently orchestrates fibroblasts' trans-differentiation, a key event in the pathogenesis of SSc.