Effect Of Selenium On The Damage Induced By Hyperhomocysteinemia On Spontaneous Hypertensive Rat Arterial Walls

Objective:Hyperhomocysteinemia is an independent risk factor of atherosclerotic disease.Clinical studies have proven that hyperhomocysteinemia(Hhcy) increases the risk of cardiovascular disease in hypertension. Animal experiments show that the aorta of spontaneous hypertensive rats(SHR) have more serious damages than that of normotensive rats after oral administration of methionine. Oxidative stress is important in Hhcy-related pathogenesis of aorta. However,the specific mechanism of Hhcy-induced oxidant stress in hypertension is unclear. Selenium is an essential trace that exerts its effects mainly through its incorporation into selenoproteins. Adequate selenium intake is needed to maximize the activity of selenoproteins, among which GPX-1 has been shown to play a major role in defense against oxidative stress. This study was designed to investigate the mechanism of HHcy-induced damage in SHR,and observe the protective effects of selenium.Metholds:Thirty 6-week-old male SHRs were randomly divided into six groups(each=5):① group normal( group Nor) :SHRs fed a Se-adequate diet until the end of the experiment;②group se-deficient(group Se-deficient):SHRs fed a se-deficient diet until the end of the experiment; ③ se-deficient+Hyperhomocysteine( group Se-deficient+Hcy):SHRs fed a se-deficient diet and injected with DL-hcy at the last three week; ④4μg/kg Na2SO3 +Hhcy(group 4μgSe+Hcy): SHRs fed a se-deficient diet and 10 days before being injected with DL-hcy supplemented with Na2SeO3(4μg/kg body weight,ip); ⑤40μg/kg Na2SO3+Hhcy(group 40μgSe+Hcy): SHRs fed a se-deficient diet and 10 days before being injected with DL-hcy supplemented with Na2SeO3( 40μg/kg body weight,ip); ⑥ 80μg/kg Na2SeO3 +Hhcy( group80μgSe+Hcy): SHRs fed a se-deficient diet and 10 days before being injected with DL-hcy supplemented with Na2SeO3(80μg/kg body weight,ip). The systolic pressure and heart rate were measured by tail cuff. The body weights were examined during the period of drug injection. Blood samples were harvested from caudal vein toanalyze the concentration of Hcy. Aorta samples were collected for the following detections: endothelium-dependent relaxation by measuring the response to acetylcholine(Ach); ROS and activity by chemilluminescent assay; ultrastructure by transmision electron microscope(TEM); morphology and collagen fibrosis by HE and masson staining; and the expression of GPX-1 by western blot analysis.Results:1. The plasma homocysteine concentration was inceased significantly in the model groups compared with the control group(p<0.01), indicating that the hyperhomocysteinemia model was established successfully. There was no detectable difference of homocysteine concentration among the groups supplemented with selenium(p>0.05).2.There was no detectable difference among six groups in the body weight and heart rate(p>0.05).The Se-deficient group and Se-deficient & Hcy group rats had increased systolic pressure( SBP) by 7-8mmHg,compared to other groups.3. Compared to control group, Se-deficient group have the following charactors:endothelial cell and mitochondrial damage, smooth muscle cells proliferation,collagen and elastin fiber increase. Importantly, the Se-deficient & Hcy group rats have the most serious changes of above parameters among all the groups. However,supplementation of selenium provented those changes in a dose-dependent mannar to a certain degree.4. A significant impairment of the vascular response to Ach was found in the aorta rings of Se-deficient group rats when compared with those isolated from the control rats(p<0.05). The vasorelaxation of aorta rings from Se-deficient & Hcy group was significantly decreased compared with the that of the Se-deficient group(p<0.05). Supplementation with selenium in a dose-dependent manner significantly enhanced endothelial- dependent vasorelaxation induced by Ach(p<0.05).5. There was a significant increase in ROS production of aorta rings from Se-deficient group rats compared with that of control group rats(p<0.05). ROS production of aorta rings from Se-deficient & Hcy group rats increased significantly compared with that of the Se-deficient group rats(p<0.05). Selenium Supplementation in a dose-dependent manner significantly decreased ROS production(p<0.05). Incubation with DPI markedly attenuated the ROS production among six groups(p<0.05),and incubation with ROT attenuated the ROS production among Se-deficient group,Se-deficient & Hcy group,and markedly attenuated the ROS production in the Se-deficient & Hcy group(p<0.05). In contrast, incubation with L-NAME had not affected the production of ROS(p>0.05).6. The activity in the aorta from Se-deficient & Hcy group rats increased significantly compared with the Nor group rats and Se-deficient group rats(p<0.05).Selenium Supplementation with in a dose-dependent manner significantly decreased activity(p<0.05).7. There was no detectable difference of the expression of GPX-1 in the aorta between control group rats and Se-deficient group rats, Se-deficient & Hcy group rats and Supplemented with selenium significantly elevated GPX-1expression of GPX-1in a dose-dependent manner(p<0.05).Conclusions:Selenium supplementation moderates endothelial dysfunction,vascular remodeling and oxidative stress induced by HHcy in SHR rats.The mechanisms of these effects might be relalated to the upregulated GPX-1 expressions,and an increase in antioxidant activity.