胱硫醚-γ-裂解酶/硫化氢体系在尿毒症加速性动脉粥样硬化中的作用及其分子机制研究

Atherosclerotic cardiovascular disease (ASCD) is the most common complication and the leading cause of death in patients with maintenance hemodialysis. The condition, with its age of onset being younger and the progress faster than that of the conventional ASCD, is referred to as uremic accelerated atherosclerosis. However, mechanism of the accelerated formation of atherosclerosis in maintenance hemodialysis patients is not yet clear. Hydrogen sulfide is a novel gas signaling molecule, which has the effects of relaxing vascular smooth muscle and inhibiting proliferation of vascular smooth muscle cells. In our recent preliminary studies, we found that the levels of plasma H2S and the expression of Cystathionine-γ-lyase(CSE) mRNA were decreased in maintenance hemodialysis patients, with the lowest seen in the maintenance hemodialysis patients with concurring carotid atherosclerosis. Furthermore, levels of plasma TGF-β1 was seen to decrease and plasma MMP-12 increase in MHD patients. We hypothesised that the CSE/H2S system disorder is involved in uremic accelerated atherosclerosis. The proposed study aims to explore the effect of CSE/H2S system on uremic accelerated atherosclerosis and its molecular mechanism on gene and protein expression levels and by in vivo and in vitro studies. The study will employ mouse model of uremic accelerated atherosclerosis, mouse aortic smooth muscle cells and involve the dialysis patients. It is hope that the study would provide the mechanistic explanation of the pathogenesis of uremic accelerated atherosclerosis and new ideas for the prevention and treatment of cardiovascular diseases in chronic kidney disease, especially in patients with end-stage renal disease.

透析患者最常见的并发症和首位死亡原因是心血管疾病，发病年龄提前且进展较快，称为加速性动脉粥样硬化。但透析患者动脉粥样硬化加速形成的机制仍未完全明确。硫化氢是一种气体信号分子，能够舒张血管平滑肌、抑制平滑肌细胞增殖。我们前期研究发现透析患者血浆硫化氢水平降低，内源性硫化氢合成酶胱硫醚-γ-裂解酶转录下调，有颈动脉粥样硬化者更低，同时其血浆TGF-β1水平下降、MMP-12水平升高。推测胱硫醚-γ-裂解酶/硫化氢体系失调可能参与尿毒症加速性动脉粥样硬化发生。为此，我们拟分别以透析患者、小鼠模型和小鼠主动脉平滑肌细胞为研究对象，通过体内和体外研究，在基因和蛋白质表达两个层面探讨胱硫醚-γ-裂解酶/硫化氢体系在尿毒症加速性动脉粥样硬化发病过程中的作用与分子机制，以期明确该病的发病机制，为慢性肾脏病、透析患者心血管疾病防治提供新思路。

动脉粥样硬化性心血管疾病是慢性肾脏病 (chronic kidney disease, CKD)，尤其是终末期肾脏病患者最常见的并发症和引起死亡的首位原因，并由于其发病年龄提前而且进展较快，称为尿毒症加速性动脉粥样硬化(uremic accelerated atherosclerosis, UAAS)。多种传统与非传统危险因素均参与了UAAS发生与发展，然而其分子机制尚不清楚。本研究发现： 1. 终末期肾病进行维持性血液透析 (chronic hemodialysis，CHD) 患者血浆硫化氢 (H2S) 水平降低，且其降低是CHD患者UAAS发生的独立危险因素，也是CHD患者心血管死亡和全因死亡的独立危险因素；2. CHD患者血浆内源性H2S合成酶胱硫醚--裂解酶 (Cystathionine-γ-lyase,CSE) mRNA表达下调，且血浆H2S水平与其颈动脉内中膜厚度进展呈负相关；同时其血浆转化生长因子-beta1 (transforming growth factor-beta1, TGF-beta1) 水平下降而血浆金属蛋白酶-12 (metal matrix proteinase-12, MMP-12) 升高，提示CSE/H2S体系可能通过调控TGF-beta/Smads信号通路影响UAAS的发生发展；3、CHD患者血浆H2S水平降低，而其外周血单个核细胞中经典型蛋白激酶C beta II (conventional protein kinase C beta II, cPKC beta II)激活，同时Akt磷酸化水平降低 (*P<0.05)，提示cPKC beta II激活可能参与了UAAS的发生及发展过程，且可能通过Akt信号通路发挥作用；3. 利用雄性载脂蛋白E敲除 (ApoE-/-) 小鼠UAAS模型发现，小鼠体内H2S水平升高可减少其UAAS的形成，而抑制小鼠体内H2S则促进UAAS发生；4. 利用培养人脐静脉内皮细胞及UAAS小鼠主动脉平滑肌细胞，发现加入H2S供体NaHS后，细胞培养液中H2S水平明显升高。总之，本研究通过多个实验证实CSE/H2S体系及其相关信号通路在UAAS形成和发展中的作用。有关成果进一步丰富了人们对终末期肾脏病CHD患者UAAS形成机制的认识，并为临床预防治疗UAAS相关疾病提供了新的思路和实验依据。