Role Of Androgen And Its Receptor In Atherosclerotic Plaque Stability And Thrombosis And Mechanisms Concerned

The basic pathology of atherothrombosis is atherosclerotic plaque rupture and sequential thrombus formation. Traditionally, it is believed that atherothrombosis is closely related with such factors as smoking, lackness of exercise, irrational diet, hypertension, lipid disorder, diabetes, obesity and metabolism syndrome. Recent studies demonstrate that the levels of testosterone decrease with the increase of age, which is related to the risk increase of male coronary heart disease, aortic or carotid atherosclerosis. Androgen receptor palys an important role in the early phase of atherosclerosis formation and the decrease of its expression is associated with the severity of atherosclerosis progress. The study of Alevizaki, et al. revealed that the androgen receptor gene CAG polymorphism is associated with the severity of coronary artery disease in men. The study of Zitzmann, et al. demonstrated that shorter, more androgenic AR alleles with fewer CAG repeats are associated with lower HDL-C.The previous studies of our group disclosed that the level of androgen is negatively related to coronary heart disease and peripheral arterial disease. However, these studies didn't suggested that low leve of androgen is a result or cause of coronary heart disease. It is conflicting view which roles androgen plays in atherosclerosis progress. Atherosclerotic plaque rupture is an early phase in the atherothrombosis formation. Presently, it is unclear whether androgen and its receptor play roles in plaque stability, which the mechanisms corncerned still were elucidated. Acute thrombus formation is an important pathological progress of atherothrombosis.Epidemiological studies demonstrated that the morbidity of cardivascular disease is higher in men than in women. The older the male is, the higher is the morbidity of atherothrombosis. These studies reveal that androgen maybe plays an important role in atherothrombosis formation. However, it is unclear whether androgen and its receptor play roles in thrombus formation, which the mechanisms corncerned still need to be studied further. The purposes of the study are to determine the influence of androgen and its receptor on atherosclerotic plaque growth, stability and arterial thrombosis,to investigate the mechanisms concerned, and to further provide interventional target and evidence for first-level prevention of atherothrombosis in the eldly male with low level of androgen.Partâ… : Regulation and mechanisms corncerned of Atherosclerotic Progress and Plaque Stability by Testosterone and Flutamide in Male RabbitsObjectives: The purposes of the study are to determine the influence of androgen and its receptor on atherosclerotic plaque growth, stability and arterial thrombosis and further to investigate the mechanisms concerned.Methods: Pathological sections of aorta were performed hematoxylin-eosin staining and Masson's trichrome staining. Total plasma testosterone was measured using ADVIA Centaur(?) Immunoassay System (Bayer, Germany), whereas DHT levels were measured using a DHT ELISA kit. The contents of serum tumor necrosis factor-α(TNFα) and interleukin-6 (IL₆) were assayed using radio-immunoassay kit. The concentrations of serum soluble intercellular adhesion molecule-1 (sICAM-1) and matrix metallopeptidase 2(MMP₂) were assayed using ELISA kit according to the procedure described by the manufacturer. The contents of plasma endothelin-1, plasma renin activity and angiontensinâ…¡were assayed using radio-immunoassay kit.Results: Our results showed that testosterone undecanoate replacement reduced the plaque area, the aortic intimal thickness and increased the fibrous cap thickness and collagen contents in castrated rabbits. However, presence of flutamide increased the plaque area, the aortic intimal thickness and decreased the fibrous cap thickness and collagen contents in castrated rabbits again. Our results still revealed that levels of serum TNF_α, IL₆, sICAM and MMP₂ increased in cholesterol-rich diet rabbits as compared with standard diet rabbits. Castration caused an increase in levels of serum TNF_α, IL₆, sICAM and MMP₂ in castrated rabbits as compared with sham-operated rabbits. Treatment of testosterone undecanoate reduced the levels of serum TNF_α, IL₆, sICAM and MMP₂ in castrated rabbits. However, presence of flutamide increased the levels of serum TNF_α, IL₆, sICAM and MMP₂ again. In our study, we didn't find that testosterone undecanoate replacement or treatment with flutamide affected the levels of plasma endothelin-1, plasma renin activity and angiontensinâ…¡in castrated rabbits as compared with sham-operated rabbits.Conclusion: Androgen and its receptor can regulate atherosclerotic plaque growth and stability, which is related to influence inflammatory reaction in male rabbits;Paretâ…¡: Roles and Mechanisms of Androgen in ferric-chloride-induced Arterial Thrombosis in RatsObjectives: The aim of our study is to elucidate roles androgen and its receptor in ferric-chloride-induced arterial thrombosis and mechanisms corncerned in ratsMethods: Castrated models and experimental thrombosis models of male rats were prepared. Platelet aggregometer was used to measure platelet aggregation, and platelet adherometer was used to measure platelet adhesion. The contents of TXB₂ and 6-Keto-PGF_1αawere assayed using radio-immunoassay kit. The intraplatelet free calcium concentrations were measured with Fluo-3/AM FCM assay. Parameters of blood coagulation and fibrinolytic system were assayed using STA-R Coagulation analyzers, and Plasma viscosity was tested using SA-6000 automated hemorrheology tester.Results: DHT replacement restored circulating DHT to physiological levels, without being altered by treatment with flutamide. Pretreatment with DHT (2nM) significantly inhibited the platelet aggregation and adhesion induced by ADP. After PRP was pretreated with flutamide, ADP-induced platelet aggregation and adhesion increased again. After castration and DHT replacement, the ratio of both TXB2 and 6-keto-PGF_1α obviously decreased. However, administration of flutamide to DHT treated castrated rats caused an increase in the proportions of both TXB₂ and 6-keto-PGFia again. DHT (2nM) replacement obviously reduced [Ca²⁺]_i,. However, Pretreatment with flutamide and DHT (2nM), [Ca²⁺]_i increase induced by ADP was observed once more.Castration caused a significant reduction in plasma testosterone and DHT levels, whereas DHT replaced at a dose of 0.25mg/rat restored circulating DHT to physiological levels, without being altered by treatment with flutamide. The plasma TXB2 increased in castrated rats as compared with that in sham-operated rats. Replacement of DHT reduced plasma TXB2 contents in castrated rats. However, flutamide supplementation increased plasma contents of TXB2 in castrated rats again. In addition, total plasma testosterone and DHT were significantly lower in castrated rats than in normal rats (7.94±3.07nmol/L vs 0.96±0.09nmol/L; 1.76±0.77nmol/L vs 0.1±0.02nmol/L, (all P<0.05). Castration caused significant increase in the thrombus area and weight in castrated rats as compared with control group (1157.38±68.74μm² vs 969.43±22.66μm²; 7.17±1.72 mg vs 5.17±1.17 mg, all P<0.05). DHT replacement restored circulating DHT to physiological levels, without being altered by treatment with flutamide. Pretreatment with DHT (2nM) significantly inhibited the platelet aggregation and adhesion induced by ADP. After PRP was pretreated with flutamide, ADP-induced platelet aggregation and adhesion increased again. After castration and DHT replacement, the ratio of both TXB2 and 6-keto-PGF_1α obviously decreased. However, administration of flutamide to DHT treated castrated rats caused an increase in the proportions of both TXB2 and 6-keto-PGF_1α again. DHT (2nM) replacement obviously reduced [Ca²⁺]_i,. However, Pretreatment with flutamide and DHT (2nM), [Ca²⁺]_i increase induced by ADP was observed once more. Prothrombin activity (PA%) was higher, and prothrombin time (PT), activated partial thromboplastin time (APTT) and international normalized ratio (INR) were lower in castrated rats than in normal rats (all P<0.05). There weren't significant difference in FIB, D-dimer and plasma between in castrated rats and in normal rats (all P>0.05).Conclusion: Androgen and its receptor regulate experimental arterial thrombosis via modulating platelet activation and coagulation processes in male rats;Partâ…¢: Inhibition of oxidative-stress-induced platelet aggregation by androgen at physiological levels via its receptor is associated with the reduction of thromboxane A₂ release from plateletsObjectives: Platelets play a crucial role in the development of arterial thrombosis and other pathophysiologies leading to clinical ischemic events. Defective regulation of platelet activation/aggregation is a predominant cause for arterial thrombosis. The purposes of our study are to assess the effect of physiological concentration of androgen via its receptor on oxidative-stress-induced platelet aggregation and to further elaborate the active mechanism.Methods: Dihydrotestosterone (DHT) was determined by ELISA using a commercially available kit. Platelet aggregometer was used to measure platelet aggregation. The contents of thromboxane B₂(TXB₂) were assayed using radio-immunoassay kit.Results: Our results showed that addition of DHT (2nM) significantly inhibited platelet aggregation induced by hydrogen peroxide (H₂O₂)(10mM, 25mM) in PRP diluted with Tyrode's buffer. Moreover, H₂O₂-induced platelet aggregation decreased in sham-operated rats. However, H₂O₂-induced platelet aggregation significantly increased in castrated rats. Replacement of DHT inhibited H₂O₂-induced platelet aggregation in castrated rats. After PRP was pretreated by flutamide, H₂O₂-induced platelet aggregation increased in castrated rats again. Presence of DHT (2nM) obviously inhibited H₂O₂-induced thromboxane A₂ (TXA₂) release in castrated rats. Pretreatment of DHT and flutamide increased H₂O₂-stimulated TXA₂ release from platelet in castrated rats again. Castration caused a significant reduction in plasma testosterone and DHT levels, whereas DHT replaced at a dose of 0.25mg/rat restored circulating DHT to physiological levels, without being altered by treatment with flutamide. The plasma TXB₂ increased in castrated rats as compared with that in sham-operated rats. Replacement of DHT reduced plasma TXB₂ contents in castrated rats. However, flutamide supplementation increased plasma contents of TXB₂ in castrated rats again.Conclusion: Androgen at physiological doses via its receptor inhibits oxidative-stress-induced platelet aggregation, which is associated with the reduction of TXA₂ release from platelets.