APOM deficiency contributes to renal failure in glomerular diseases

项目总结 脂质诱导的足细胞损伤是一种新出现的促进糖尿病进展的分子途径 代谢性和非代谢性肾小球疾病(GDS)。其他人和我们的研究强调了一个 胆固醇逆向转运受损和鞘磷脂代谢改变在脂质诱导中的作用 GDS的足细胞损伤，然而，调节RCT和鞘磷脂代谢的一个常见的可用药途径 足细胞仍有待鉴定。 在多种脂蛋白中，载脂蛋白M(ApoM)主要存在于高密度脂蛋白(Hdl)中。 促进RCT向高密度脂蛋白转化的颗粒，但也充当运送鞘氨醇-1-磷酸的伴侣 (S1P)通过循环。S1P信号通过apom/S1P复合体与S1P受体结合而发生 (S1PR1-5)，它调节许多生理过程，包括迁移、增殖和细胞生存。 我们最近发现肾小球载脂蛋白(GAPOM)mRNA表达显著降低。 GD患者登记在海王星队列中。我们新的初步数据显示，gapom减少 与血浆载脂蛋白(PAPOM)降低、肾小球鞘氨醇激酶1(SPHK1)升高、 将鞘氨醇转化为S1P的酶，S1PR4的表达和EGFR的下降。我们观察到一个 在GD的小鼠模型Col4A3 KO小鼠和Col4A3 KO足细胞中，基因表达谱相似，这 与肾小球/足细胞胆固醇和S1P积聚有关，这是由于RCT和激活受损所致 重组人载脂蛋白阻止S1P/S1PR4信号通路导致细胞凋亡增加 (RhAPOM)治疗。重要的是，重组人APOM对防止COL4A3细胞凋亡的治疗作用 KO足细胞优于SPHK1或S1PR4拮抗剂。最后，我们演示了对人类的治疗 含有外源性S1P的足细胞增加足细胞凋亡并导致微流体装置中的白蛋白泄漏 以及apom缺陷的Col4A3KO小鼠。 基于这些观察，我们假设GDS代表GAPOM缺陷引起的一种状态 足细胞RCT和激活S1P/S1PR信号受损，从而导致脂毒性足细胞损伤。我们 提出一种高度翻译的方法，具有三个具体目标：1)研究gAPOM缺陷是否与 随着肾小球S1P/S1PR信号的激活，与pAPOM水平下降相关，并预测 GD患者的结局：2)研究足细胞载脂蛋白缺乏对RCT和S1P/S1PR4的影响 3)在实验模型中研究重组人载脂蛋白的治疗潜力。 我是说。 如果成功，这项转译研究可能导致apom作为GDS生物标记物的临床发展。 以及重组载脂蛋白作为治疗GDS的新方法的应用。

PROJECT SUMMARY Lipid-induced podocyte injury is an emerging molecular pathway contributing to the progression of glomerular diseases (GDs) of metabolic and non-metabolic origin. Research by others and us has highlighted a role for impaired reverse cholesterol transport (RCT) and altered sphingolipid metabolism in lipid-induced podocyte injury in GDs, yet, a common druggable pathway regulating both RCT and sphingolipid metabolism in podocytes remains to be identified. Among several lipoproteins, Apolipoprotein M (APOM) is mainly located in high density lipoprotein (HDL) particles where it facilitates RCT to HDL but also acts as a chaperone to transport sphingosine-1-phosphate (S1P) through the circulation. S1P signaling occurs through binding of APOM/S1P complexes to S1P receptors (S1PR1-5), which regulate many physiological processes, including migration, proliferation, and cell survival. We recently demonstrated significantly decreased glomerular APOM (gAPOM) mRNA expression in patients with GD enrolled in the NEPTUNE cohort. Our new preliminary data show that decreased gAPOM correlates with decreased plasma APOM (pAPOM), with increased glomerular sphingosine kinase 1 (SPHK1), the enzyme that converts sphingosine to S1P, and S1PR4 expression and with eGFR decline. We observed a similar gene expression pattern in Col4a3 KO mice, a mouse model of GD, and in Col4a3 KO podocytes, which was associated with glomerular/podocyte cholesterol and S1P accumulation due to impaired RCT and activation of S1P/S1PR4 signaling leading to increased apoptosis which was prevented by recombinant human APOM (rhAPOM) treatment. Importantly, the therapeutic effect of rhAPOM in preventing podocyte apoptosis in Col4a3 KO podocytes was superior to SPHK1 or S1PR4 antagonism. Finally, we demonstrate that treatment of human podocytes with exogenous S1P increases podocyte apoptosis and causes albumin leakage in a microfluid device as well as in ApoM deficient Col4a3 KO mice. Based on these observations, we hypothesize that GDs represent a state of gAPOM deficiency causing impaired RCT and activation S1P/S1PR signaling in podocytes, thereby causing lipotoxic podocyte injury. We propose a highly translational approach with three specific aims to 1) investigate if gAPOM deficiency correlates with the activation of glomerular S1P/S1PR signaling, is associated with decreased pAPOM levels and predicts outcomes in patients with GD, 2) to investigate the role of podocyte APOM deficiency on RCT and S1P/S1PR4 signaling, and 3) to investigate the therapeutic potential of recombinant human APOM in an experimental model of GD. If successful, this translational study may lead to the clinical development of APOM as a biomarker in GDs and to the use of recombinant APOM as a novel therapy for GDs.