miR-146a在UVA诱导皮肤成纤维细胞光老化中作用机制的研究

Photoaging is cell aging caused by long-wave ultraviolet (UVA) radiation, which is the main cause of human skin aging produced by exogenous environment. How to delay skin photoaging has become an important scientific issue all over the world. As an endogenous non-coding small RNA, miRNAs modulate gene expression through paired binding with target gene sequences and miRNAs play essential roles in cell growth and development. miRNAs are sensitive to environmental change and the expression change of miRNAs is an important manner to adjust to environment. During UVA induced photoaging, it is our center to investigate whether miRNAs are responsive to UVA to participate in the UVA caused stress reaction of skin cells and then to discover specific miRNAs which can antagonize the UVA induced photoaging. The fibroblast of dermis is the main target site of UVA, so we established the in vitro photoaging model with UVA radiated human primary cultured fibroblasts, which was proved to be photoaged. To screen the differential miRNAs in photoaging, we revealed some differentially expressed miRNAs with gene chip, including 5 up- and 8 down-regulated miRNAs, which was verified by qRT-PCR analysis.We found that miRNA146a was correlated with inflammation negative regulation caused by UVA, and then we presumed that it could regulate its target gene SMAD4 and other classical aging associated proteins (such as p21) to participate in photoaging. Sequential work will focus on searching for miRNA146a targets and proving that miRNA146a plays important roles through targeting that target gene. We will also discover more functional miRNAs and their target genes and provide theoretic foundation for developing drug target of photoaging.

长波紫外线（UVA）照射所致的细胞老化是人类皮肤受外源环境影响产生衰老的最主要因素。miRNAs对外源环境非常敏感，是机体适应外界环境的重要调控方式。光老化中 miRNAs是否对UVA照射产生响应并参与调节皮肤细胞对UVA的应激反应是本课题研究的核心，以期发掘能够拮抗UVA导致的光老化的miRNAs。本课题组前期通过UVA照射人原代皮肤成纤维细胞构建光老化模型，筛选出差异表达miRNAs，发现miR-146a与调节紫外线辐射后炎症负调控相关，并推测其能通过调控编码的SMAD4等基因进而调节p21等经典的老化相关蛋白参与细胞的光老化进程，后续工作将着重围绕miRNA146a的靶基因，并用功能实验证实miRNA-146a是通过调控其靶基因的表达来发挥功能。我们也将发掘更多功能性的差异miRNAs及其靶基因，为研发光老化的药物靶点提供理论支持。

长波紫外线（UVA）照射所致的细胞老化是人类皮肤受外源环境影响产生衰老的最主要因素。miRNAs对外源环境非常敏感，是机体适应外界环境的重要调控方式。光老化中 miRNAs是否对UVA照射产生响应并参与调节皮肤细胞对UVA的应激反应是本课题研究的核心，以期发掘能够拮抗UVA导致的光老化的miRNAs。本课题组以UVA照射人原代皮肤成纤维细胞构建光老化模型筛选出差异表达miRNA-146a为研究靶点，研究其调控基因在光老化中可能存在的机制。通过细胞水平的研究，我们发现miRNA-146a可能通过其靶点基因SMAD4在炎症负调控中发挥其抗光老化的作用。NF-κB也是UVA上调的靶点基因，上调NF-κB蛋白的表达可促进细胞光老化进程，抑制其表达具有一定的光保护作用，但研究发现在光老化进程中NF-κB并未对miRNA146a及其靶基因SMAD4起到调控作用。此外研究还发现miRNA-146a也可能通过调控其靶点基因MED1在光老化中发挥作用，其具体机制可能与其调控成纤维细胞内DNA甲基化水平相关联，紫外线照射后DNA处于明显的低甲基化状态，细胞凋亡率增加，增殖活性下降。同时在动物实验中，我们通过UVA辐射小鼠背部去毛皮肤构建光老化模型，在体研究光老化的作用机制，研究显示光老化小鼠皮肤内miRNA146a表达量出现下调，P53、P21、P16等老化相关蛋白表达亦出现上调表达，miRNA146a的靶点基因SMAD4和MED1亦出现一定水平的过量表达，与前期细胞水平的观察研究一致。因此通过本课题的研究结果，我们推测UVA辐射诱导成纤维细胞及小鼠皮肤光老化的过程中， miRNA146a可能通过其靶基因SMAD4和MED1对光老化进程有一定调控作用，为研发抗光老化的药物基因靶点提供理论支持。