ADP-ribosylation in experimental atherosclerosis: a potential link between dyslipidemia and inflammation in cardiovascular disease

Multimodal inflammation and lipid accumulation are major features of atherosclerosis, a leading cause of death and morbidity worldwide. Our previous study recognized ADP-ribosylation, a post-translational modification, as a novel regulator of macrophage-induced inflammation and atherogenesis.2 Our recent ADP-ribosylome study using an acute inflammation mouse model demonstrated that systemic IFN-gamma administration induced changes to the ADP-ribosylation of lipid-binding and macrophage-associated proteins in the liver and spleen of wild-type mice, respectively. We also identified ADP-ribosylated apolipoproteins A-I and A-II (APOA1, APOA2) in the liver of wild-type mice. In this current study, we investigated the ADP-ribosylome of the atherosclerotic aorta derived from low-density lipoprotein receptor-deficient (Ldlr-/-) mice. Mice were fed a regular chow diet or a high-fat diet (HFD) for 3 or 6 months before harvesting the aorta, liver, and plasma. ADP-ribosylome enrichment from mouse aorta presented several challenges that were overcome by pooling 10 aortae per diet/month group, and applying our unique and recently optimized ion mobility mass spectrometry strategy to increase ADP-ribosyl peptide signals. The increased prevalence of ADP-ribosylated apolipoproteins in both liver and aorta of HFD-fed mice suggests that the liver secreted them as lipoproteins which eventually accumulated in the aorta. In particular, ADP-ribosylation sites predominated the C-terminus of APOA1. As C-terminal helices of APOA1 are important for lipid binding, engagement of ABCA1 in smaller HDL particles, and the interaction of lipid-free APOA1 with macrophages and specific lipid efflux, disturbance in the ADP-ribosylation of this region could impair the protein’s functions.

多模态炎症与脂质蓄积是动脉粥样硬化的核心病理特征，而动脉粥样硬化是全球范围内致死与致残的首要病因之一。我们既往研究已证实，翻译后修饰过程ADP-核糖基化（ADP-ribosylation）是巨噬细胞介导炎症与动脉粥样硬化发生的新型调控因子[2]。我们近期利用急性炎症小鼠模型开展的ADP-核糖基化修饰组（ADP-ribosylome）研究显示，全身性给予干扰素γ（IFN-γ）可分别诱导野生型小鼠肝脏与脾脏内脂质结合蛋白及巨噬细胞相关蛋白的ADP-核糖基化水平发生改变。本研究团队同时还在野生型小鼠肝脏中鉴定出了ADP-核糖基化修饰的载脂蛋白A-I与A-II（APOA1、APOA2）。本研究中，我们针对低密度脂蛋白受体缺陷型（Ldlr-/-）小鼠的动脉粥样硬化主动脉开展ADP-核糖基化修饰组学分析。实验小鼠分别接受常规饲料或高脂饲料（HFD）喂养3个月或6个月后，采集其主动脉、肝脏与血浆样本。从小鼠主动脉中富集ADP-核糖基化修饰肽段存在诸多技术难点，我们通过将每个饮食/喂养时长组的10根主动脉样本混合，并采用本团队新近优化的专属离子迁移质谱策略以提升ADP-核糖基化肽段的信号强度，成功克服了上述难题。高脂饲料喂养小鼠的肝脏与主动脉中，ADP-核糖基化载脂蛋白的检出率均有所升高，这提示肝脏将这些修饰后的载脂蛋白以脂蛋白形式分泌，最终在主动脉中发生蓄积。尤为值得关注的是，APOA1的C端区域富集了大量ADP-核糖基化修饰位点。由于APOA1的C端螺旋结构对于脂质结合、介导ATP结合盒转运蛋白A1（ABCA1）参与小型高密度脂蛋白（HDL）颗粒形成，以及无脂质结合的APOA1与巨噬细胞的相互作用和特异性脂质外流过程均至关重要，该区域的ADP-核糖基化修饰紊乱可能会损害该蛋白的生理功能。