Pleiotropic Effects of Statins in Cardiac Arrhythmia and Coagulability

• Main Authors: Sheng-Nan Chang, 張勝南
• Other Authors: 江福田
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/n6r2j3

博士 === 國立臺灣大學 === 臨床醫學研究所 === 106 === Atrial fibrillation (AF) is the most common arrhythmia in clinical practice, and is associated with thromboembolic stroke. Recent studies have demonstrated the role of inflammation in the mechanism of AF. C-reactive protein (CRP) is closely related with inflammation reaction. Therefore, our project is designed to investigate the effect of serum CRP level and genetic polymorphisms of CRP on the incidence of thromboembolic events in patients with AF. Furthermore, statins are well clinically used for anti-inflammation, we also try to investigate how statins prevent inflammation-related pro-coagulation by basic cellular studies. In the section I of the project, a genetic association study between CRP gene polymorphisms and AF was performed in two independent populations (I: 100 AF patients and 101 controls; II: 348 AF patients and 356 controls). Three polymorphisms (T-861C, A-821G and C-390A⁄ C-390T) were found in the 1-kb promoter of CRP. A triallelic polymorphism (C-390A⁄ C-390T) captured all haplotype information and determined the CRP gene promoter activity and the plasma CRP level, and was in nearly complete linkage disequilibrium with G1059C polymorphism in exon 2. The -390A variant was associated with a higher CRP gene promoter activity, a higher plasma CRP level and a higher risk of AF. Patients with AF also had a higher plasma CRP level than controls. CRP significantly increased the inward L-type calcium current in atrial myocytes with no changes in other ionic currents. CRP did not affect the expressions of type I alpha 1 (COL1A1), type III alpha 1 (COL3A1) and type 1 alpha 2 (COL1A2) procollagens in atrial fibroblasts. In the section II of the project, a total of 725 AF patients were longitudinally followed-up for more than 10 years. CRP gene promoter triallelic polymorphism (C-390A/C-390T) were genotyped and CRP levels were checked. After adjustment for conventional risk factors, patients with higher CRP levels were more likely to develop thromboembolic stroke compared to those with the lowest CRP quartile (hazard ratio= 2.27, 95% confidence interval 1.08-4.81; the lowest CRP quartile as the reference group). Patients carrying the A-390 or T-390 allele had higher CRP levels (3.35±2.71 vs 2.43±2.00 mg/L), and were more likely to develop thromboembolic stroke, even after adjustment for conventional risk factors (hazard ratio= 2.07, 95% confidence interval 1.23-3.48). In the section III of the project, we conducted the study to investigate the potential molecular mechanisms for the anti-thrombotic effect of statins. Cultured human hepatoma cells (HepG2) were used as the in vitro model. The human protein C gene promoter was cloned into the luciferase reporter to study the transcriptional regulation of human protein C gene. Wistar rats fed with simvastatin (5 mg • kg–1 • d–1) were used as the in vivo model. We found simvastatin increased the expression of protein C in hepatocytes (361±64% and 313±59% after 2 hrs and 6 hrs of stimulation, respectively, both p< 0.01). In the animal study, the serum protein C levels were increased in the simvastatin treated group (8.4 ± 3.2 unit/ml in controls vs. 22.7 ± 15.2 unit/ml for 1 week, and 20.3 ± 16.9 unit/ml for 2 weeks, respectively, both p< 0.05). The level of hepatocyte nuclear factor 1α (HNF1α) was also increased in both the in vivo and in vitro models. We found that the protein C promoter activity was increased by simvastatin, and this effect was inhibited by HNF1α knockdown and constitutively active Rac1. Our project identify inflammation-related genetic risk factors for AF occurrence, AF-related thromboembolic events, and establish the beneficial effects of statins in reducing AF complication.