乙酰化KLF4/6和促炎因子启动子上组蛋白调控MsPGN炎性病变的分子机制

Human mesangial proliferative glomerulonephritis (MsPGN) is a disease with high incidence, and the immunologic inflammation leading to damages is a difficult problem of medical research field in the world. Our previous studies demonstrated that the production of pro-inflammatory cytokines (TNF-α, IL-18, MCP-1 and Rantes) and infiltration of inflammatory T cells and macrophages were seen in the renal tissue of rats with Thy-1 nephritis (a model of MsPGN). Given that the transcription coactivator PCAF with acetyltransferase activity and transcriptional factor KLF4 and KLF6 were significantly co-upregulated both in the renal tissue of rat Thy-1 nephritis and in the glomerular mesangial cells (GMC) stimulated with sublytic C5b-9 complex, and in order to elucidate the mechanism of transcriptional regulation on production of the pro-inflammatory cytokines in the GMC upon sublytic C5b-9 stimulation, we attempt to explore the role of KLF4 or KLF6, including the effects of acetylated KLF4 or KLF6 and histone located in promoters of the pro-inflammatory cytokines on the gene transcription of these cytokines. The purpose of our study is to reveal molecular and epigenetic mechanism in the expression of pro-inflammatory cytokines and renal damage in the rat with Thy-1 nephritis, and further to provide an evidence for preventing and treating human MsPGN.

人类系膜增生性肾小球肾炎（MsPGN）发病率高，其肾组织免疫炎性病变是医学界难题之一。我们发现，大鼠Thy-1肾炎（MsPGN模型）发病早期，肾组织中有促炎因子（TNF-α、IL-18、MCP-1和Rantes）生成和T细胞及Mφ浸润。鉴于具有乙酰转移酶活性的转录辅激活因子（PCAF）和转录因子（KLF4、KLF6）均是Thy-1肾炎大鼠肾组织和亚溶解型补体攻膜复合物（即sublytic C5b-9）诱导肾小球系膜细胞（GMC）早期明显上调的共表达基因，故为了探讨sublytic C5b-9诱导促炎因子的转录调控机制，本研究拟从体内和体外探索KLF4、KLF6的作用及其PCAF乙酰化修饰这两种转录因子和促炎因子启动子上组蛋白致其染色质重塑后对前述促炎因子基因转录的影响。旨在为揭示Thy-1肾炎生成促炎因子和炎性病变的分子机制（包括表观遗传学调控），并为今后防治人类MsPGN提供科学依据。

系膜增生性肾炎（MsPGN）是人类常见的肾脏疾病，其肾内不仅可见C5b-9的沉积，而且还有促炎因子的明显增多，但两者之间的关系并不明了。大鼠Thy-1肾炎（Thy-1N）是研究MsPGN的动物模型。Thy-1N大鼠肾中既有C5b-9的形成，也有促炎因子的升高，且其病变还有sublytic C5b-9的依赖性。体外用sublytic C5b-9攻击肾小球系膜细胞（GMC）后可诱导合成一些促炎因子或介质。不过目前有关sublytic C5b-9启动促炎因子生成的作用及机制并未阐明。本研究利用Thy-1N模型和大鼠的GMCs实验发现，Thy-1N大鼠肾组织及sublytic C5b-9刺激的GMCs中不仅可见IL-23和IL-36a的升高，而且还见转录因子KLF4 和转录辅激活因子PCAF的上调，且KLF4与PCAF的表达时相接近，均早于IL-23和IL-36a的产生。此外，在sublytic C5b-9刺激GMCs后，KLF4能通过与IL-23和IL-36a启动子结合调控IL-23和IL-36a的转录。另PCAF经KLF4结合两因子的启动子也可调控其转录。再者，sublytic C5b-9刺激GMCs还能诱导PCAF与KLF4结合, 且PCAF可乙酰化KLF4第224位赖氨酸（K224），并由此增加了KLF4与IL-23和IL-36a启动子的结合，最终上调了两种促炎因子的表达。体内沉默肾内KLF4和PCAF基因后既能抑制Thy-1N大鼠IL-23和IL-36a的生成，又可降低GMC的增生和蛋白尿的分泌。提示，Thy-1N大鼠发病时，sublytic C5b-9确能诱导促炎因子的产生，其机制不仅涉及到上调的转录因子和转录辅激活因子共同参与，而且还与转录因子的乙酰化修饰相关。以上研究成果为防治人类MsPGN提供了有用的实验依据。