孕期脂多糖暴露对子代大鼠血压的跨代遗传效应及表观遗传机制

Prenatal lipopolysaccharide (LPS) exposure results in increased blood pressure in F1 generation. Our preliminary result showed this effect could pass to F2 generation. Both the F1 and F2 generations showed decreased sodium excretion and increased renal AT1R-induced urinary sodium retention, indicating that the enhanced AT1R function may play an important role in the transgenerational genetic effects of blood pressure. Our previous studies showed that GRK4 could positively regulate AT1R function and protein expression, and the SHR showed decreased methylation in promoter of GRK4, and increased mRNA and protein expression, but reversed to normal after treatment of 5-azacitidine, a inhibitor of methylation transferase. We found that both of the F1 and F2 generations showed increased GRK4 mRNA and protein expression, but restored significantly after 5-azacitidine treatment. So, we presumed that demethylation of GRK4 promoter may play an important role in increased GRK4 mRNA level and enhanced AT1R-induced sodium retention in F1 and F2 generations. Our study will provide a new idea on genetic mechanism for hypertension.

孕期免疫炎症刺激可引起子代（F1）血压升高。我们前期实验发现该效应可通过跨代遗传影响到F2代子鼠。F1、F2代子鼠均表现为基础状态下24小时尿钠排泄功能降低以及肾脏AT1R介导的尿钠潴留作用增强，提示AT1R功能增强可能是血压跨代遗传效应的重要原因。我们前期表明，GRK4可以正向调节AT1R功能, SHR大鼠随着血压升高GRK4启动子区甲基化程度降低， mRNA及蛋白表达升高，而我们发现F1、F2代子鼠肾脏GRK4 mRNA及蛋白表达水平均显著升高；当使用甲基化转移酶抑制剂后表达均显著恢复。 因此，我们推测GRK4启动子区去甲基化可能是F1、F2代子鼠肾脏GRK4 mRNA表达升高及AT1R介导的尿钠潴留作用增强的重要原因。该项目拟研究并证实孕期免疫炎症刺激可能通过GRK4表观遗传修饰调节AT1R功能进而导致连续子代血压跨代遗传效应，并为高血压的遗传机理提供新的认识。

孕期脂多糖暴露可致大鼠子代高血压。我们发现该效应有跨代遗传现象，子代伴有尿钠排泄障碍，通过对F1和F2代肾脏mRNA芯片分析，发现Ras相关C3肉毒素底物I(Rac1)在F1和F2的肾脏表达均增加，伴有盐皮质激素受体(MR)胞浆减少，入核增加。用Rac1特异抑制剂处理子代，发现尿钠代谢及血压均明显恢复，且用MR拮抗剂安体舒通处理子代，发现尿钠代谢及血压也有明显恢复，推测肾脏Rac1-MR信号轴的激活是高血压跨代遗传的主要机制。另外，发现孕期LPS暴露可导致子代大鼠肾脏组蛋白H3K9me2表达下降， H3K9me2能够调控Rac1的表达。孕期LPS刺激后的子一代大鼠肾脏和血浆氧化应激指标（MDA）升高，抗氧化指标（SOD）下降。但是子二代和子三代没有明显差异。且用氧化应激抑制剂Temple处理子一代大鼠，能够有效降低其血压。因此，通过本研究发现孕期LPS刺激后ROS水平上升、H3K9me2表达下降，致Rac1启动子区低甲基化和Rac1高表达；这种Rac1的低甲基化可稳定遗传给子代，持续激活子代Rac1-MR信号轴，致水钠代谢障碍，并最终导致高血压跨代遗传。该项目的研究为高血压跨代遗传的机制提供了新认识。