The Wnt antagonists DKK1 and SFRP1 are downregulated by promoter hypermethylation in systemic sclerosis
The Wnt antagonists DKK1 and SFRP1 are downregulated by promoter hypermethylation in systemic sclerosis
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DOI：
10.1136/annrheumdis-2012-203194
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发表时间：
2014-06-01
影响因子：
27.4
通讯作者：
Distler, Joerg H. W.
中科院分区：
文献类型：
--
作者：
Dees, Clara;Schlottmann, Inga;Distler, Joerg H. W.
目的激活Wnt信号并降低内源性抑制物的表达是近年来系统性硬化症(SSC)的一种中枢病理机制。异常的表观遗传修饰也有助于SSC成纤维细胞的持续激活。我们研究了SSC中Wnt信号的增加和表观遗传学的改变是否与启动子超甲基化导致Wnt拮抗剂沉默有关。方法采用甲基化特异性聚合酶链式反应方法检测内源性Wnt拮抗剂在白细胞和成纤维细胞中的甲基化状态。用5-氮杂-2‘-脱氧胞苷抑制成纤维细胞DNA甲基转移酶(DNMT)和博莱霉素诱导的小鼠皮肤纤维化模型。结果SSC患者成纤维细胞和外周血单个核细胞中Dkk1和SFRP1启动子高甲基化。在SSC中，启动子高甲基化导致Dkk1和SFRP1转录受损，表达降低。用5-aza处理SSC成纤维细胞或博莱霉素攻击的小鼠可以阻止启动子甲基化诱导的沉默，并将这两个基因的表达提高到正常水平。结论Dkk1和SFRP1启动子的高甲基化与SSC中异常的Wnt信号转导有关，Dnmt抑制有效地降低了Wnt信号转导。这些数据提供了表观遗传学改变和SSC中Wnt信号增加之间的新联系，也具有翻译意义，因为DNMT抑制剂已经被批准用于临床。
Objective Activated Wnt signalling with decreased expression of endogenous inhibitors has recently been characterised as a central pathomechanism in systemic sclerosis (SSc). Aberrant epigenetic modifications also contribute to the persistent activation of SSc fibroblasts. We investigated whether increased Wnt signalling and epigenetic changes in SSc are causally linked via promoter hypermethylation-induced silencing of Wnt antagonists.Methods The methylation status of endogenous Wnt antagonists in leucocytes and fibroblasts was evaluated by methylation-specific PCR. 5-aza-2'-deoxycytidine was used to inhibit DNA methyltransferases (Dnmts) in cultured fibroblasts and in the mouse model of bleomycin-induced skin fibrosis. Activation of Wnt signalling was assessed by analysing Axin2 mRNA levels and by staining for beta-catenin.Results The promoters of DKK1 and SFRP1 were hypermethylated in fibroblasts and peripheral blood mononuclear cells of patients with SSc. Promoter hypermethylation resulted in impaired transcription and decreased expression of DKK1 and SFRP1 in SSc. Treatment of SSc fibroblasts or bleomycin-challenged mice with 5-aza prevented promoter methylation-induced silencing and increased the expression of both genes to normal levels. Reactivation of DKK1 and SFRP1 transcription by 5-aza inhibited canonical Wnt signalling in vitro and in vivo and effectively ameliorated experimental fibrosis.Conclusions We demonstrate that hypermethylation of the promoters of DKK1 and SFRP1 contributes to aberrant Wnt signalling in SSc and that Dnmt inhibition effectively reduces Wnt signalling. These data provide a novel link between epigenetic alterations and increased Wnt signalling in SSc and also have translational implications because Dnmt inhibitors are already approved for clinical use.