中國科學院上海生命科學研究院健康科學研究所沈南教授領導的研究組整合上海交通大學附屬仁濟醫院風濕科的臨床優勢和健康所的基礎研究力量，繼2009年在風濕病學領域最有影響力的雜志ARTHRITIS & RHEUMATISM上報道了miRNA作為負反饋調節分子在狼瘡關鍵致病通路中起了重要作用后，近日又在國際學術期刊Journal of immunology發表了有關miRNA參與狼瘡T細胞低甲基化調控的最新研究成果。該工作揭示了miRNA參與狼瘡發病的新機制，為今后發展miRNA為靶點的干預治療提供了重要依據。

系統性紅斑狼瘡(systemic lupus erythematosus, SLE) 發病機理復雜，被認為是自身免疫病的原型，T淋巴細胞異常低甲基化在SLE的發病中起著重要作用。但狼瘡T細胞異常低甲基化的機制尚未闡明。MicroRNA(miRNA)是近年來廣為關注的重要的基因表達調控因子，SLE患者T細胞異常低甲基化可能與某些miRNA異常表達有關。

為探索這一關鍵問題，研究人員通過高通量和特異性的miRNA表達譜分析、篩選發現，miR-21和miR-148a在SLE小鼠模型T淋巴細胞異常高表達。探索miR-21和miR-148a的表達與疾病臨床表型的相關性，發現在SLE患者T細胞中這兩個miRNA的表達水平與疾病的活動性以及免疫相關的甲基化敏感基因的表達呈正相關。進一步機制研究發現，狼瘡T細胞中高表達的miR-21通過直接抑制DNMT1上游信號分子RASGRP1而間接調控DNMT1的表達，miR-148a通過直接靶向DNMT1的編碼區來調控DNMT1的表達，加速細胞內低甲基化狀態，誘導自身免疫相關的甲基化敏感基因啟動子區域去甲基化，上調敏感基因的表達，介導疾病發生。使用這兩個miRNA特異性抑制劑對SLE病人T淋巴細胞進行干預處理，發現能夠有效逆轉低甲基化狀態。

該項研究表明，miR-21和miR-148a有望成為調控SLE患者T淋巴細胞異常低甲基化的新靶點，改變SLE患者T淋巴細胞內的miR-21和miR-148a表達水平可作為潛在的干預治療手段。

該項工作得到國家科技部、國家自然科學基金和上海市科委的經費支持。

點擊此處了解更多

MicroRNA-21 and MicroRNA-148a Contribute to DNA Hypomethylation in Lupus CD4+ T Cells by Directly and Indirectly Targeting DNA Methyltransferase Wen Pan,* Shu Zhu, Min Yuan,* Huijuan Cui,* Lijia Wang,* Xiaobing Luo,* Jia Li,* Haibo Zhou,*, Yuanjia Tang,*, and Nan Shen*,

*Joint Molecular Rheumatology Laboratory, Institute of Health Sciences and Shanghai Renji Hospital, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Shanghai Jiaotong University School of Medicine,? Laboratory of Immunity and Diseases, Institute of Health Sciences, and? Key Laboratory of Stem Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China

【Abstract】Systemic lupus erythematosus is a complex autoimmune disease caused by genetic and epigenetic alterations. DNA methylation abnormalities play an important role in systemic lupus erythematosus disease processes. MicroRNAs (miRNAs) have been implicated as fine-tuning regulators controlling diverse biological processes at the level of posttranscriptional repression. Dysregulation of miRNAs has been described in various disease states, including human lupus. Whereas previous studies have shown miRNAs can regulate DNA methylation by targeting the DNA methylation machinery, the role of miRNAs in aberrant CD4+ T cell DNA hypomethylation of lupus is unclear. In this study, by using high-throughput microRNA profiling, we identified that two miRNAs (miR-21 and miR-148a) overexpressed in CD4+ T cells from both patients with lupus and lupus-prone MRL/lpr mice, which promote cell hypomethylation by repressing DNA methyltransferase 1 (DNMT1) expression. This in turn leads to the overexpression of autoimmune-associated methylation-sensitive genes, such as CD70 and LFA-1, via promoter demethylation. Further experiments revealed that miR-21 indirectly downregulated DNMT1 expression by targeting an important autoimmune gene, RASGRP1, which mediated the Ras–MAPK pathway upstream of DNMT1; miR-148a directly downregulated DNMT1 expression by targeting the protein coding region of its transcript. Additionally, inhibition of miR-21 and miR-148a expression in CD4+ T cells from patients with lupus could increase DNMT1 expression and attenuate DNA hypomethylation. Together, our data demonstrated a critical functional link between miRNAs and the aberrant DNA hypomethylation in lupus CD4+ T cells and could help to develop new therapeutic approaches.