miR-31负向调节SLC15A4介导pDCs-IFNⅠ轴异常在SLE发病机制中的作用研究

The excessive activation of IFN I pathway resulted from the abnormal regulation of plasmacytoid dendritic cells (pDCs)-type I interferon(IFN I) and the abnormality of innate immune response is one of the important links in the pathogenesis of systemic lupus erythematosus(SLE). Solute carrier family 15, member 4(SLC15A4) is one of susceptibility genes for SLE and it is a critical regulating factor in type I IFN production. The strong correlation between the two SNPs in SLC15A4-3'UTR region and the clinical phenotypes and disease activity of SLE has been verified in our previous studies. Then the close relationship between miR-31 and SLC15A4-3'UTR region was predicted by some databases. At the same time, other studies showed that down-regulated expression of miR-31 in peripheral blood cell from SLE patients and there was strong correlation between the down-regulated miR-31 and the disease activity of SLE. Thus we speculate that the negative regulation of miR-31 to SLC15A4 is reduced in pDCs，and then overactive IFNI pathway enhances the downstream inflammation response, which finally promotes the initiation and development of SLE. In the study, we will first analyze the relationship between miR-31 and SLC15A4 expression. Further in vitro and in vivo by knockout lupus-like mice, the effects of miR-31 negatively regulating SLC15A4 on pDCs-IFN I axis and its downstream inflammation pathways. It is very important to clarify the regulation mechanism of the autoimmune inflammatory reaction of SLE and it may lay a foundation for the targeted therapy of SLE.

浆细胞样树突状细胞(pDCs)-Ⅰ型IFN轴调节异常致IFNⅠ通路过度活化以及天然免疫异常是SLE发病的重要环节，SLC15A4作为SLE的易感基因，是调节pDCs产生IFNⅠ的关键因素。我们前期研究证实SLC15A4-3’UTR区2个SNPs与SLE临床表型及疾病活动性密切相关,进一步通过数据库预测提示miR-31与该SNPs区域高度相关。同时有研究证实SLE外周血miR-31表达降低且与狼疮活动性相关。由此推测pCDs中miR-31对SLC15A4负向调节作用减弱，使IFNⅠ通路过度活化，下游炎症应答增强，从而促进SLE发生发展。本课题拟先分析miR-31和SLC15A4的表达及其相互作用，体外及基因敲除狼疮鼠体内研究miR-31对SLC15A4的负向调节对pDCs-IFNⅠ轴及其下游炎症通路的影响，明确其对SLE自身免疫性炎症反应的调节作用，为寻找SLE新的治疗靶点提供实验依据。

浆细胞样树突状细胞(pDCs)-Ⅰ型IFN轴调节异常致Ⅰ型IFN通路过度活化以及天然免疫异常是SLE发病的重要环节，SLC15A4作为SLE的易感基因，是调节pDCs产生Ⅰ型IFN的关键因素。课题组前期研究发现SLC15A4在SLE患者PBMC中表达显著升高，且SLC15A4-3’UTR区2个SNPs与SLE临床表型及疾病活动性密切相关，通过数据库预测提示miR-31与该SNPs区域高度相关。在此基础上通过检测SLE患者PBMC中miR-31及SLC15A4表达水平，及其与IFNⅠ相关炎症因子及SLE临床疾病活动性指标间的相关性分析，体外细胞水平验证miR-31与SLC15A4之间的作用靶点及其对下游I型IFN相关基因的表达调控，最后狼疮鼠动物模型体内进一步验证miR-31间的负性调节作用对pDCs-Ⅰ型IFN轴的影响。研究结果表明，miR-31-5p对SLC15A4产生负向调节作用，miR-31-5p通过直接靶向作用于SLC15A4调节其表达水平及其下游I型IFN相关炎症因子表达。有趣的是，研究过程中我们发现miR-506-3p对SLC15A4具有和miR-31-5p相似的调节作用。SLE患者PBMC中miR-31-5p及miR-506-3p均低表达，SLC15A4表达水平与其呈负相关，高表达的SLC15A4通过激活IRF通路，促进I型IFN产生及干扰素刺激基因FILT3、MX1、OSA1等表达，I型IFN相关炎症因子的产生，导致SLE自身免疫性炎症的形成。该研究结果进一步表明SLC15A4是pDCs-IFNⅠ轴的关键性调控分子之一，而SLC15A4可能受多种不同分子机制调控，此结果对阐明SLE自身免疫性炎症反应的调节机制，尤其明确了SLC15A4对I型IFN相关炎症调节的关键作用，为探索SLE的潜在治疗靶点提供了新的实验依据。