钠钾对Dahl盐敏感大鼠肾髓质PHD2/HIF-1α通路的影响及机制研究

Excess salt intake is an important environmental risk factor for the predisposition to essential hypertension. Previous studies reported that hypoxia-inducible factor (HIF) 1α and its target genes, such as NO synthase, cyclooxygenase 2, and hemeoxygenase 1, are highly expressed in the renal medulla. These HIF-1α target genes play critical roles in the maintenance of sodium homeostasis, and prolyl hydroxylase (PHD) is the key molecule of adjusting HIF-1α. We have found high salt intake can increase renal medullary PHD2, and reduce the levels of HIF-1α and its target genes in Dahl salt-sensitive rats, which promotes the occurrence and development of salt-sensitive hypertension, and potassium supplementation may counteract the effect of sodium. But it is unclear that potassium and sodium influence PHD/HIF-1α pathway by which approach. We hypothesized that inflammation is one of the mechanisms, causing impaired PHD2 response to high salt in Dahl salt-sensitive rats. Potassium supplementation can improve this impairment. Our group will combine molecular biology techniques with animal experiments, considering Dahl salt-sensitive and SS13BN rats as the research models, using immunohistochemistry, Real time RT-PCR and Western blotting methods, exploring the important mechanism of impaired PHD2 response to high salt intake and whether potassium supplement has therapeutic effect by changing the renal medullary PHD2/HIF-1α channel in Dahl salt-sensitive rats. Our study will help to elucidate the molecular mechanism of salt-sensitive hypertension and provide the theoretical bases and molecular targets for the treatment of salt-sensitive hypertension.

钠盐是高血压的一个重要易患因素。文献报道，肾髓质缺氧诱导因子（HIF）1α及其靶基因在维持钠平衡方面发挥重要作用，而脯氨酰羟化酶（PHD）是调节HIF-1α的关键分子。本课题组前期预实验发现，高盐摄入升高Dahl大鼠肾髓质PHD2水平，降低HIF-1α及其靶基因水平，促进了盐敏感性高血压的发生发展；补钾可拮抗这一变化。但钠钾通过何种途径影响该通路尚不清楚。为此，我们提出假说：炎症是引起Dahl大鼠肾髓质PHD2对高盐反应受损的重要机制之一；补钾能起到一定逆转作用。本研究将以Dahl盐敏感和SS13BN大鼠为动物模型，采用Real-time RT-PCR、Western blotting等方法进行深入研究，探索Dahl大鼠肾髓质PHD2对高盐反应受损的机制和补钾是否通过改变PHD2/HIF-1α通路，从而对盐敏感性高血压起到治疗作用，为阐明盐敏感性高血压发生的分子机制和临床治疗提供理论依据。

盐敏感性高血压是当前心血管领域研究的热点内容之一，肾脏钠钾代谢紊乱是盐敏感性形成的主要机制。本课题组前期研究发现，补钾有拮抗高盐引起的血压升高、防止高血压发生的保护作用，尤其对盐敏感者更为显著，但其机制有待进一步阐明。本研究在我们既往研究基础上采用新的研究思路，以Dahl盐敏感大鼠和SS13BN大鼠为研究模型，给予钠钾和酶抑制剂干预4周后应用实时定量PCR检测肾髓质PHD2和 HIF-1α mRNA表达；采用免疫组化和Western blotting方法检测肾髓质PHD2、HIF-1α及其靶基因COX-2、NOS2蛋白水平；采用ELISA检测血清纤溶酶原激活物抑制剂-1、纤维蛋白原和FKN水平；免疫比浊法检测血清hsCRP水平，化学比色法检测肾髓质纤溶酶原激活物抑制剂-1、纤维蛋白原和FKN水平。通过观察钠钾对肾髓质炎性指标、PHD2、HIF-1α及其靶基因表达的影响，进一步探讨了DS大鼠肾髓质PHD2对高盐反应受损的重要机制和补钾的治疗作用。本研究结果显示高盐摄入能升高Dahl盐敏感大鼠肾髓质PHD2水平，同时降低HIF-1α及其靶基因水平，在盐敏感性高血压的发生发展中发挥作用；同时发现炎症是引起Dahl盐敏感大鼠肾髓质PHD2对高盐反应受损的重要机制之一。 补钾在一定程度上通过改变肾髓质PHD/HIF-1α通路从而对盐敏感性高血压起到治疗作用。这对进一步揭示盐敏感性高血压的发生机制，指导高血压临床诊治和人群防治具有重大理论意义和实际应用价值。本课题的完成拓展了人们对盐敏感性高血压发生机制的认识，为研究环境因素（钠钾摄入）在盐敏感性高血压中的作用提供了思路，并为临床治疗提供了新的依据。