PARP15 promotes vascular barrier integrity in inflammation

The vascular endothelial barrier, which supports balanced plasma solute and macromolecule composition, controls hemostasis, and limits leukocyte extravasation at homeostasis, is frequently disrupted in inflammation associated with sepsis and other critical illness. Monoclonal gammopathy-associated idiopathic systemic capillary leak syndrome (ISCLS, Clarkson disease) is a rare and devastating disorder characterized by relapsing-remitting episodes of spontaneous, profound microvascular hyper-permeability. A loss of function (LOF) mutation (G628R) in the mono ADP-ribosyltransferase PARP15, a protein of unknown function that is absent in mice, is associated with ISCLS and correlates with clinical markers of severe vascular leakage. In vascular endothelial cells, PARP15 suppresses cytokine-induced barrier disruption by ADP-ribosylating the scaffold protein JNK-interacting protein 3 (JIP3) and inhibiting p38 MAP kinase activation. Mice expressing human wild type (WT) PARP15 have curtailed inflammation-associated vascular leakage compared to mice expressing PARP15(G628R) in a p38-dependent fashion. Thus, PARP15 is essential for vascular endothelial barrier function under inflammatory stress. To investigate the functional effects of PARP15 G268R mutation on endothelial cell function, we conducted RNAseq on mutant and control microvascular endothelial cells, both stimulated and unstimulated.

血管内皮屏障（vascular endothelial barrier）可维持血浆溶质与大分子成分的稳态平衡、调控止血过程，并在生理稳态下限制白细胞外渗，但其功能常于脓毒症及其他重症疾病相关的炎症状态下受损。单克隆丙种球蛋白病相关性特发性系统性毛细血管渗漏综合征（ISCLS，克拉克森病）是一种罕见且毁灭性的疾病，以自发性、严重的微血管高通透性复发缓解发作为特征。小鼠体内不表达、功能尚未明确的单ADP核糖基转移酶PARP15发生功能丧失（LOF）突变（G628R），与ISCLS发病相关，且与严重血管渗漏的临床标志物存在显著关联。在血管内皮细胞（vascular endothelial cells）中，PARP15可通过对支架蛋白JNK相互作用蛋白3（JIP3）进行ADP核糖基化修饰，并抑制p38丝裂原活化蛋白激酶（p38 MAP kinase）的激活，从而抑制细胞因子诱导的屏障破坏。相较于以p38依赖方式表达PARP15(G628R)的小鼠，表达人野生型（WT）PARP15的小鼠其炎症相关性血管渗漏症状得到显著缓解。综上，PARP15对于炎症应激状态下的血管内皮屏障功能至关重要。为探究PARP15 G268R突变对内皮细胞功能的影响，我们对刺激组与未刺激组的突变型及对照微血管内皮细胞开展了RNA测序（RNAseq）。