Sodium pump inhibitors in blood pressure regulation and in profibrotic signaling in salt sensitive hypertension and aging

MBG在动物模型中以及在培养的大鼠血管平滑肌细胞和心肌细胞中激活了两种促纤维化途径，Fli 1依赖性和TGF-β依赖性。在高血压Dahl盐敏感大鼠和血压正常的Sprague-Dawley大鼠的心血管和肾组织中，在高盐摄入的情况下，通过升高的MBG激活TGF-β依赖性途径。我们证明了（i）Fli 1依赖性和TGF-β依赖性促纤维化途径在磷酸化PKC-δ水平上表现出串扰，（ii）这些途径被独立或同时激活，（iii）促纤维化信号传导的激活与血压无关。 Dahl盐敏感大鼠（DSS）对高盐（HS）饮食的高血压反应伴随着中央动脉硬化（CAS）和内源性Na/K-ATP酶抑制剂海蟾毒配基（MBG）水平升高，海蟾毒配基是一种促高血压和促纤维化因子。CAS是痴呆症的危险因素。我们研究了体内施用MBG或HS饮食对年轻DSS和血压正常的Sprague-Dawley大鼠（SD）（DSS的遗传背景）的血压、CAS和行为功能的影响。 8周龄雄性SD和DSS给予HS饮食（8%NaCl; n=18/组）或低盐饮食（LS; 0.1%NaCl; n=14-18/组）8周，或通过渗透微泵给予MBG（n=15-18/组）4周。MBG处理组接受LS饮食。实验结束后测定收缩压（SBP）、脉搏波传导速度（PWV）、CAS指标、MBG、Morris水迷宫（MWM）和组织化学分析。 与SD-LS相比，DSS-LS的SBP和PWV较高，空间记忆较差。与LS对照组相比，应激源HS和MBG的给药增加了两种品系的PWV、SBP和主动脉壁胶原蛋白丰度。在SD中，HS和MBG给药与SD-LS对照相比，不影响通过超声心动图（ECHO）评估的心脏参数，其中与DSS一样，在DS-HS与DS-LS中，HS饮食后观察到全心脏结构和功能受损。MBG治疗不影响DSS-MBG与DSS-LS的ECHO参数。HS饮食导致SD和DSS的内源性血浆和尿MBG增加。因此，HS的促高血压和促纤维化作用可至少部分归因于MBG增加。MBG的促高血压和促纤维化功能在DSS和SD中都是显著的，尽管定量PCR揭示了MBG或HS激活的DSS和SD中促纤维化基因的不同谱。空间记忆不受HS饮食或MBG治疗的影响，而不是在SD，也不是在DSS。 结论：与年轻的SD-LS相比，年轻的DSS-LS总体上更高的血压、CAS和心血管重构可能是认知功能受损的基础。MBG和HS对DSS和SD大鼠心血管系统和功能的影响接近，但SD大鼠的变化率低于DSS大鼠。增加的PWV和血压对空间记忆的累积效应的缺乏可以通过年轻大鼠的脑可塑性来解释，这有助于动物维持升高的CAS并抵消MBG的促纤维化效应。

Two pro-fibrotic pathways, Fli1-dependent and TGF-beta-dependent, are activated by MBG in the animal models, and in the cultured rat vascular smooth muscle cells and cardiac myocytes. The TGF-beta-dependent pathway is activated by heightened MBG in the presence of a high salt intake in cardiovascular and renal tissues from hypertensive Dahl salt-sensitive rats and normotensive Sprague-Dawley rats. We demonstrated (i) that Fli1-dependent and TGF-beta-dependent pro-fibrotic pathways exhibit a crosstalk at the level of phosphorylated PKC-delta, (ii) that these pathways are activated either independently, or simultaneously, and (iii) that the activation of the profibrotic signaling is blood pressure independent. Hypertensive response in Dahl Salt-Sensitive rats (DSS) on a high salt (HS) diet is accompanied by central arterial stiffening (CAS) and heightened levels of an endogenous Na/K-ATPase inhibitor, marinobufagenin (MBG), a pro-hypertensive and profibrotic factor. CAS is a risk factor for dementia. We studied the effect of the in vivo administration of MBG or HS diet on blood pressure, CAS and behavioral function in young DSS and normotensive Sprague-Dawley rats (SD), a genetic background for DSS. Eight weeks old male SD and DSS were given HS diet (8% NaCl; n=18/group), or low salt diet (LS; 0.1% NaCl; n=14-18/group) for 8 weeks, or MBG (n=15-18/group) administered via osmotic minipumps for 4 weeks. The MBG-treated groups received LS diet. Systolic blood pressure (SBP), pulse wave velocity (PWV), a marker of CAS, MBG, Morris water maze (MWM) test to measure spatial memory and the tissue collection for the histochemical analysis were assessed at the end of the experiment. DSS-LS had higher SBP and PWV and worst spatial memory than SD-LS. The administration of stressors, HS and MBG, increased PWV, SBP and aortic wall collagen abundance in both strains vs. their LS controls. In SD, HS and MBG administration did not affect heart parameters, assessed by echocardiography (ECHO), vs. SD-LS control, where as in DSS, the impaired whole-heart structure and function were observed after HS diet in DSS-HS vs. DSS-LS. MBG treatment did not affect the ECHO parameters in DSS-MBG vs. DSS-LS. HS diet led to increase of an endogenous plasma and urine MBG in both SD and DSS. Thus, the pro-hypertensive and profibrotic effect of HS can be at least partially attributed to MBG increase. The pro-hypertensive and profibrotic functions of MBG were pronounced in both DSS and SD, although quantitative PCR revealed different profiles of profibrotic genes in DSS and SD activated by MBG or HS. Spatial memory was not affected by HS diet or MBG treatment not in SD, nor in DSS. Conclusions: Overall higher blood pressure, CAS and cardiovascular remodeling may underlie the impaired cognitive functions in young DSS-LS in comparison to young SD-LS. MBG and HS had near similar effects on cardiovascular system and function in DSS and SD rats, although the rate of changes vs. control in SD was lower than that in DSS rats. The absence of the cumulative effect of the increased PWV and blood pressure on spatial memory can be explained by the brain plasticity in young rats, which helped the animals to sustain the elevated CAS and to counterbalance the profibrotic effects of MBG.