Shenzhen Key Laboratory of Molecular Epidemiology (Y.X., J.X., J.C., Y.Z., YK.), Shenzhen Center for Disease Control and Prevention, Guangdong, China.
Key Laboratory of Modern Toxicology of Shenzhen (H.H., X.Y.), Shenzhen Center for Disease Control and Prevention, Guangdong, China.
Circulation. 2019 May 7;139(19):2260-2277. doi: 10.1161/CIRCULATIONAHA.118.036336.
Elevated levels of S-adenosylhomocysteine (SAH), the precursor of homocysteine, are positively associated with the risk of cardiovascular disease and with the development and progression of atherosclerosis. However, the role of SAH in endothelial dysfunction is unclear.
Apolipoprotein E-deficient ( apoE) mice received dietary supplementation with the SAH hydrolase (SAHH) inhibitor adenosine dialdehyde or were intravenously injected with a retrovirus expressing SAHH shRNA. These 2 approaches, along with the heterozygous SAHH gene knockout ( SAHH) mouse model, were used to elevate plasma SAH levels and to examine the role of SAH in aortic endothelial dysfunction. The relationship between plasma SAH levels and endothelial dysfunction was also investigated in human patients with coronary artery disease and healthy control subjects.
Plasma SAH levels were increased in SAHH mice and in apoE mice after dietary administration of adenosine dialdehyde or intravenous injection with SAHH shRNA. SAHH mice or apoE mice with SAHH inhibition showed impaired endothelium-dependent vascular relaxation and decreased nitric oxide bioavailability after treatment with acetylcholine; this was completely abolished by the administration of the endothelial nitric oxide synthase inhibitor N-nitro-l-arginine methyl ester. Furthermore, SAHH inhibition induced production of reactive oxygen species and p66shc expression in the mouse aorta and human aortic endothelial cells. Antioxidants and p66shc siRNA prevented SAHH inhibition-induced generation of reactive oxygen species and attenuated the impaired endothelial vasomotor responses in high-SAH mice. Moreover, inhibition of SAHH induced hypomethylation in the p66shc gene promoter and inhibited expression of DNA methyltransferase 1. Overexpression of DNA methyltransferase 1, induced by transduction of an adenovirus, was sufficient to abrogate SAHH inhibition-induced upregulation of p66shc expression. Finally, plasma SAH levels were inversely associated with flow-mediated dilation and hypomethylation of the p66shc gene promoter and positively associated with oxidative stress levels in patients with coronary artery disease and healthy control subjects.
Our findings indicate that inhibition of SAHH results in elevated plasma SAH levels and induces endothelial dysfunction via epigenetic upregulation of the p66shc-mediated oxidative stress pathway. Our study provides novel molecular insight into mechanisms of SAH-associated endothelial injury that may contribute to the development of atherosclerosis.
URL: https://www.clinicaltrials.gov . Unique identifier: NCT03345927.
S-腺苷同型半胱氨酸（SAH）水平升高，同型半胱氨酸的前体，与心血管疾病风险以及动脉粥样硬化的发生和进展呈正相关。然而，SAH 在血管内皮功能障碍中的作用尚不清楚。
载脂蛋白 E 缺陷（apoE）小鼠接受 SAH 水解酶（SAHH）抑制剂腺苷dialdehyde 的饮食补充或静脉注射表达 SAHH shRNA 的逆转录病毒。这两种方法，以及杂合子 SAHH 基因敲除（SAHH）小鼠模型，被用于升高血浆 SAH 水平，并研究 SAH 在主动脉内皮功能障碍中的作用。在患有冠状动脉疾病的人类患者和健康对照者中，还研究了血浆 SAH 水平与内皮功能障碍之间的关系。
在给予腺苷 dialdehyde 饮食或静脉注射 SAHH shRNA 后，SAHH 小鼠和 apoE 小鼠的血浆 SAH 水平升高。SAHH 抑制的 SAHH 小鼠或 apoE 小鼠在用乙酰胆碱处理后表现出受损的内皮依赖性血管舒张和降低的一氧化氮生物利用度；这完全被内皮型一氧化氮合酶抑制剂 N-硝基-L-精氨酸甲酯的给药所消除。此外，SAHH 抑制诱导了小鼠主动脉和人主动脉内皮细胞中活性氧的产生和 p66shc 表达。抗氧化剂和 p66shc siRNA 防止了 SAHH 抑制诱导的活性氧的产生，并减轻了高 SAH 小鼠受损的内皮血管舒缩反应。此外，SAHH 抑制导致 p66shc 基因启动子的低甲基化，并抑制 DNA 甲基转移酶 1 的表达。通过转导腺病毒诱导的 DNA 甲基转移酶 1 的过表达足以消除 SAHH 抑制诱导的 p66shc 表达上调。最后，在患有冠状动脉疾病的患者和健康对照者中，血浆 SAH 水平与血流介导的扩张呈负相关，与 p66shc 基因启动子的低甲基化呈负相关，与氧化应激水平呈正相关。
我们的研究结果表明，SAHH 的抑制导致血浆 SAH 水平升高，并通过 p66shc 介导的氧化应激途径的表观遗传上调引起内皮功能障碍。我们的研究为与 SAH 相关的内皮损伤的机制提供了新的分子见解，这些机制可能有助于动脉粥样硬化的发生。
网址：https://www.clinicaltrials.gov。独特标识符：NCT03345927。
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