BAG3在糖尿病血管病变高糖"代谢记忆"中的作用及其机制研究

Vascular complications are the main cause of diabetic patients with high morbidity and high mortality. It is evident that metabolic memory, whereby diabetic vascular complications continue to develop and progress in individuals who returned to normal glycemic control after a period of transient hyperglycemia, has long lasting effects. The mechanisms underlying metabolic memory remain largely unclarified. BAG3 is a member of BAG family with multiple cellular functions. Recent studies imply an important role of BAG3 in cardiac diseasese.Normal tissues seldom express BAG3, except for cardiomyocyte and skeletal muscle cells, but many stressful stimuli induce its expression. For the first time, we found that BAG3 expression was increased with continued passages in cultured primary rat vascular smooth muscle cells (VSMCs). We also demonstrated that high glucose increased BAG3 expression and promoted its nuclear translocation. Importantly, transient exposure to high glucose resulted in lasted increase in BAG3 expression and nuclear localization. We also demonstrated that BAG3 positively regulated the expression of inflammatory factors. Collectively, our previous data indicated that increase in BAG3 expression and its nuclear localization may play a potential role in metabolic memory of VSMCs. The current project aims to clarify the role of BAG3 in metabolic memory of diabetic vascular complications, as well as the underlying mechanisms. This project may enhance our understanding on metabolic memory of diabetic vascular complications, and may provide a potential target for combating with diabetic vascular complications.

血管并发症是糖尿病患者高发病率和高死亡率的主要原因。糖尿病患者在血糖得到控制后，慢性炎症和血管病变持续进展，提示存在高血糖"代谢记忆"。但高血糖"代谢记忆"分子机制远未阐明。BAG3是共分子伴侣BAG家族一员，发挥许多生物学功能。最新研究表明BAG3在心脏疾病中发挥重要功能。除心肌和骨骼肌外，正常组织很少表达BAG3，但在许多应激情况下，BAG3可被诱导表达。我们前期研究首次发现随传代次数增加，原代大鼠血管平滑肌细胞开始表达BAG3。高糖增加BAG3的表达并促进其向核内的转运，并且在短暂高糖处理恢复常糖培养后，该效果持续存在。另外，我们发现BAG3的表达水平与炎性因子表达正相关。这些结果提示BAG3表达增加及其核内定位可能与血管平滑肌细胞的高糖"代谢记忆"有关。本项目拟阐明BAG3在糖尿病血管平滑肌细胞高糖"代谢记忆"中的作用及其可能机制，可能为糖尿病血管病变的治疗带来全新的思路和方法。

BAG3过表达HUVEC细胞在常糖培养条件下增殖速率明显延缓，不能长期稳定传代，b-gal染色显示BAG3过表达促进HUVEC细胞衰老。高糖培养诱导HUVEC细胞衰老，而BAG3过表达HUVEC细胞对高糖耐受能力增强，BAG3过表达HUVEC细胞抵抗高糖诱导的细胞衰老。相反，高糖培养HUVEC细胞成管能力明显下降，而BAG3过表达HUVEC细胞在高糖条件下成管能力明显增加。另外，我们发现高糖在翻译后水平稳定BAG3的表达，并且BAG3的高表达通过转录和转录后水平诱导SASP，即衰老相关分泌表型。这些结果提示BAG3在高糖状态下可能对内皮细胞具有保护作用，而在常糖下，BAG3的过表达可能诱导HUVEC内皮细胞的衰老。在糖尿病肾病大鼠肾小管上皮细胞中BAG3蛋白表达。另外，本研究发现AUF1在糖尿病肾病中表达增加，并且AUF1的高表达参与肾间质纤维化的进程，我们发现AUF1在转录后水平调节Nedd4L表达，进而调节Smad2和Smad3磷酸化水平可能是其参与肾间质纤维化的机制之一。另外，我们还发现AUF1与BAG3相互作用，可能共同参与肾间质纤维化的进展。