Chen Kai, Zhou Xiaoli, Sun Zhongjie
From the Department of Physiology, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City (K.C., X.Z., Z.S.); and Department of Cardiology, the First Affiliated Hospital, Chongqing Medical University, Chongqing, China (X.Z.).
Hypertension. 2015 Nov;66(5):1006-13. doi: 10.1161/HYPERTENSIONAHA.115.06033. Epub 2015 Aug 31.
The prevalence of arterial stiffness increases with age, whereas the level of the aging-suppressor protein klotho decreases with age. The objective of this study is to assess whether haplodeficiency of klotho gene causes arterial stiffness and to investigate the underlying mechanism. Pulse wave velocity, a direct measure of arterial stiffness, was increased significantly in klotho heterozygous (klotho(+/-)) mice versus their age-matched wild-type (WT) littermates, suggesting that haplodeficiency of klotho causes arterial stiffening. Notably, plasma aldosterone levels were elevated significantly in klotho(+/-) mice. Treatment with eplerenone (6 mg/kg per day IP), an aldosterone receptor blocker, abolished klotho deficiency-induced arterial stiffening in klotho(+/-) mice. Klotho deficiency was associated with increased collagen and decreased elastin contents in the media of aortas. In addition, arterial matrix metalloproteinase-2, matrix metalloproteinase-9, and transforming growth factor-β1 expression and myofibroblast differentiation were increased in klotho(+/-) mice. These klotho deficiency-related changes can be blocked by eplerenone. Protein expression of scleraxis, a transcription factor for collagen synthesis, and LC3-II/LC3-I, an index of autophagy, were upregulated in aortas of klotho(+/-) mice, which can be abolished by eplerenone. In cultured mouse aortic smooth muscle cells, aldosterone increased collagen-1 expression that can be completely eliminated by small interfering RNA knockdown of scleraxis. Interestingly, aldosterone decreased elastin levels in smooth muscle cells, which can be abolished by small interfering RNA knockdown of Beclin-1, an autophagy-related gene. In conclusion, this study demonstrated for the first time that klotho deficiency-induced arterial stiffening may involve aldosterone-mediated upregulation of scleraxis and induction of autophagy, which led to increased collagen-1 expression and decreased elastin levels, respectively.
动脉僵硬度的患病率随年龄增长而增加，而衰老抑制蛋白α-klotho的水平则随年龄下降。本研究的目的是评估α-klotho基因单倍体不足是否会导致动脉僵硬度，并探讨其潜在机制。脉搏波速度是动脉僵硬度的直接测量指标，与年龄匹配的野生型（WT）同窝小鼠相比，α-klotho杂合子（klotho(+/-)）小鼠的脉搏波速度显著增加，这表明α-klotho单倍体不足会导致动脉僵硬。值得注意的是，klotho(+/-)小鼠的血浆醛固酮水平显著升高。使用醛固酮受体阻滞剂依普利酮（每天6 mg/kg，腹腔注射）治疗可消除klotho(+/-)小鼠中α-klotho缺乏诱导的动脉僵硬。α-klotho缺乏与主动脉中膜胶原蛋白增加和弹性蛋白含量减少有关。此外，klotho(+/-)小鼠的动脉基质金属蛋白酶-2、基质金属蛋白酶-9和转化生长因子-β1表达以及肌成纤维细胞分化增加。这些与α-klotho缺乏相关的变化可被依普利酮阻断。胶原蛋白合成转录因子硬骨素和自噬指标LC3-II/LC3-I的蛋白表达在klotho(+/-)小鼠的主动脉中上调，这可被依普利酮消除。在培养的小鼠主动脉平滑肌细胞中，醛固酮增加胶原蛋白-1表达，而通过小干扰RNA敲低硬骨素可完全消除这种增加。有趣的是，醛固酮降低平滑肌细胞中的弹性蛋白水平，而通过小干扰RNA敲低自噬相关基因Beclin-1可消除这种降低。总之，本研究首次证明，α-klotho缺乏诱导的动脉僵硬可能涉及醛固酮介导的硬骨素上调和自噬诱导，分别导致胶原蛋白-1表达增加和弹性蛋白水平降低。
