Remodelling of the endothelial cell transcriptional program via paracrine and DNA-binding activities of MPO [polyA-enriched total RNA-Seq]

Myeloperoxidase (MPO) is an enzyme, which functions in host defence by catalysing the formation of reactive oxygen intermediates. Synthesized majorly by myeloid progenitor cell types and neutrophils MPO is released into vascular lumen during inflammation, where it may adhere and internalize the endothelial cells coating vascular walls. Here we describe the moonlighting properties of MPO and its regulation of gene transcription in endothelial cells upon nuclear internalization. We show that MPO independently of its enzymatic activity possess chromatin binding properties in vitro and in cyto. Upon nuclear translocation, MPO changes chromatin condensation. Locally at sites of binding, MPO drives de-condensation of chromatin and at the regions flanking MPO binding sites drives an increased chromatin condensation. MPO-guided changes in chromatin condensation lead to activation of endothelial-to-mesenchymal transition in ECs and enhanced migratory potential. Moreover, MPO directly binds to the double-stranded RNA binding protein and transcription factor ILF3 and facilitates translocation of its isoform NF90 into the nucleus. This results in positive regulation of expression of VEGFA, as well lowered stability of CXCL1 and CXCL8 transcripts due to loss of cytoplasmic ILF3. Overall design: polyA-enriched mRNA profiles of MPO treated and mock treated HUVECs

髓过氧化物酶（Myeloperoxidase，MPO）是一种酶，通过催化活性氧中间产物的生成参与宿主防御反应。该酶主要由髓系祖细胞及中性粒细胞合成，在炎症过程中被释放至血管腔，可黏附并内化覆盖血管壁的内皮细胞。本研究阐述了MPO的兼职功能，以及其在细胞核内化后对内皮细胞基因转录的调控作用。研究发现，MPO不依赖其酶活性，在体外及细胞内均具有染色质结合能力。进入细胞核后，MPO会改变染色质凝缩状态：在MPO结合位点局部，该酶可介导染色质解凝缩；而在结合位点侧翼区域，则会促进染色质凝缩程度升高。MPO介导的染色质凝缩状态改变，可诱导内皮细胞-间充质转化，并提升细胞迁移能力。此外，MPO可直接结合双链RNA结合蛋白兼转录因子ILF3，并促进其异构体NF90向细胞核内转位。这一过程可正向调控血管内皮生长因子A（VEGFA）的表达；同时由于胞质ILF3的减少，CXCL1与CXCL8转录本的稳定性会降低。实验整体设计：经MPO处理与模拟处理的人脐静脉内皮细胞（Human Umbilical Vein Endothelial Cells，HUVECs）的polyA富集mRNA表达谱。