Effect of simvastatin on endothelium-dependent vaso-relaxation and endogenous nitric oxide synthase inhibitor

AIM: To investigate the effect of simvastatin on endothelium-dependent vasorelaxation and endogenous nitric oxide synthesis inhibitor asymmetric dimethylarginine (ADMA) in rats and cultured ECV304 cells. METHODS: Endothe-lial injury was induced by a single injection of low density lipoprotein (LDL) (4 mg/kg, 48 h) in rats or incubation with LDL (300 mg/L) or oxidative-modified LDL (100 mg/L) in cultured ECV304 cells, and vasodilator responses to acetylcholine (ACh) in the aortic rings and the level of ADMA, nitrite/nitrate (NO) and tumor necrosis factor-alpha (TNF-α) in the serum or cultured medium were determined. And the adhesion of the monocytes to endothe-lial cells and the activity of dimethylarginine dimethylaminohydrolase (DDAH) in the cultured ECV304 cells were measured. RESULTS: A single injection of LDL decreased endothelium-dependent relaxation to ACh, markedly increased the serum level of endogenous ADMA and TNF-α, and reduced serum level of NO. Pretreatment with simvastatin (30 or 60 mg/kg) markedly attenuated inhibition of vasodilator responses to ACh, the increased level of TNF-α and the decreased level of NO by LDL, but no effect on serum concentration of endogenous ADMA. In cultured ECV304 cells, LDL or ox-LDL markedly increased the level of ADMA and TNF-α and potentiated the adhesion of monocytes to endothelial cells, concomitantly with a significantly decrease in the activity of DDAH and serum level of NO. Pretreatment with simvastatin (0.1, 0.5, or 2.5 μmol/L) markedly decreased the level of TNF-α and the adhesion of monocytes to endothelial cells, but did not affect the concentration of endogenous ADMA and the activity of DDAH. CONCLUSION: Simvastatin protect the vascular endothelium against the damages induced by LDL or ox-LDL in rats or cultured ECV304 cells, and the beneficial effects of simvastatin may be related to the reduction of inflammatory cytokine TNF-α level.     

Effect of fenofibrate on LDL-induced endothelial dysfunction in rats

Previous investigations have demonstrated that asymmetric dimethylarginine (ADMA) is an important factor contributing to endothelial dysfunction, and that fenofibrate has a protective effect on the endothelium in hyperlipidaemic patients. In the present study in rats treated with native low-density lipoprotein (nLDL), we addressed the question of whether the beneficial effect of fenofibrate on endothelial cells is related to reduction of the ADMA concentration. A single injection of nLDL (4 mg/kg, 48 h) markedly reduced endothelium-dependent relaxation in response to acetylcholine and the plasma level of nitrite/nitrate and increased the plasma concentrations of ADMA, malonyldialdehyde (MDA) and tumour necrosis factor- (TNF-). Treatment with fenofibrate (30 or 100 mg/kg) significantly reduced the inhibition of vasodilator responses to acetylcholine, decreased the elevated levels of ADMA, MDA and TNF-, and enhanced the decreased level of nitrite/nitrate in the rats treated with LDL. These results suggest that the protective effect of fenofibrate on endothelial cells in rats treated with LDL may be related to the reduction of ADMA concentration.     

Aspirin protected against endothelial damage induced by LDL： role of endogenous NO synthase inhibitors in rats

AIM: To study the protective effect of aspirin on damages of the endothelium induced by low-density lipoprotein (LDL), and whether the protective effect of aspirin is related to reduction of nitric oxide synthase inhibitor level.METHODS: Vascular endothelial injury was induced by a single injection of native LDL (4 mg/kg) in rats. Vasodilator responses to acetylcholine (ACh) in the isolated aortic rings were determined, and serum concentrations ofasymmetric dimethylarginine (ADMA), malondialdehyde (MDA), tumour necrosis factor-α (TNF-α), and the activity of dimethylaminohydrolase (DDAH) were measured. RESULTS: A single injection of LDL (4 mg/kg)significantly decreased vasodilator responses to ACh, increased the serum level of ADMA, MDA, and TNF-α, anddecreased DDAH activity. Aspirin (30 or 100 mg/kg) markedly reduced the inhibition of vasodilator responses toACh by LDL, and the protective effect of aspirin at the lower dose was greater compared with high-dose aspiringroup. Aspirin inhibited the increased level of MDA and TNF-α induced by LDL. Aspirin at the dose of 30 mg/kg,but not at higher dose (100 mg/kg), significantly reduced the concentration of ADMA and increased the activity ofDDAH. CONCLUSION: Aspirin at the lower dose (30 mg/kg) protects the endothelium against damages elicitedby LDL in vivo, and the protective effect of aspirin on endothelium is related to reduction of ADMA concentrationby increasing DDAH activity.     

A reduction of endogenous asymmetric dimethylarginine contributes to the effect of captopril on endothelial dysfunction induced by homocysteine in rats

We examined whether captopril exerts beneficial effect on homocysteine-induced endothelial dysfunction in vivo and whether this effect of captopril is associated with a reduction of endogenous inhibitor of nitric oxide synthase (NOS) asymmetric dimethylarginine (ADMA) in rats. Male Sprague-Dawley rats were given intravenous injections of homocysteine (10 mg/kg/day) to induce endothelial dysfunction. Captopril treatment (3 mg/kg/day, i.v.) was taken in some rats after homocysteine administration. Endothelium-dependent relaxation was tested in aortic rings. Serum levels of ADMA, nitrite/nitrate, malondialdehyde (MDA), and creatinine were measured. Furthermore, superoxide dismutase activity in liver and angiotensin converting enzyme activity in serum were also assayed. Administration of homocysteine to rats for 4 weeks significantly impaired endothelium-dependent relaxation compared with control rats. This impairment of endothelium-dependent relaxation was accompanied by elevated serum concentration of ADMA and decreased serum content of nitrite/nitrate. Moreover, serum concentration of MDA was remarkably increased, whereas liver superoxide dismutase activity was decreased in homocysteine-treated group compared with control. Chronic captopril treatment not only improved the impaired endothelium-dependent relaxation, but also prevented the elevation of serum ADMA and MDA levels, as well as reduction of serum nitrite/nitrate contents and liver superoxide dismutase activity. Serum angiotensin converting enzyme activity and creatinine had no significant difference between the three groups. These results suggest that chronic captopril treatment reduces endogenous inhibitor of NOS in rats with homocysteine injection, which may contribute to the beneficial effect of captopril on homocysteine-induced endothelial dysfunction in vivo, and may be secondary to the antioxidative action of captopril.     

Quercetin antagonism of Bay K 8644 effects on rat tail artery L-type Ca(2+) channels

Macroangiopathy is a major complication of diabetes mellitus in which dysfunction of vascular endothelium induced by excessive oxidative stress is an early and key determinant. As an endogenous antioxidant, taurine possesses endothelial protective effect in vitro. LOX-1 is an endothelial receptor for oxidized low-density lipoprotein (oxLDL) which might mediate endothelial dysfunction and subsequent atherogenesis in diabetes. We used streptozotocin-induced rats as models of type 1 diabetes to evaluate the protective effect of taurine against vascular endothelial dysfunction in type 1 diabetes and the possibly involved molecule mechanism. Eight male Wistar rats were used as normal control group. Sixteen diabetic rats induced by one single injection of streptozocin (60 mg/kg, i.p.) were randomly divided into two groups after the diabetes onset: diabetes mellitus group and taurine-treated diabetes group. 6 weeks afterward, endothelium-dependent vasodilation of isolated thoracic aorta, serum oxLDL and soluble intercellular adhesion molecule (sICAM-l) levels, LOX-1 and intercellular adhesion molecule (ICAM-1) expression on aortas were determined respectively. Streptozocin-induced diabetic rats were complicated with excessive oxidative stress and endothelial dysfunction: increased serum oxLDL and sICAM-1, inhibited endothelium-dependent vasodilator responses to acetylcholine (1 nM-0.1 microM). Simultaneously, LOX-1 and ICAM-1 expression were enhanced in aortas of diabetic rats; whereas blunted endothelium-dependent vasodilator responses to acetylcholine, increased serum oxLDL and sICAM-1 level as well as overexpression of LOX-1 and ICAM-1 were all attenuated significantly by taurine treatment. In conclusion, taurine improves vascular endothelial dysfunction induced by experimental type 1 diabetes and this effect might be associated with downregulation of LOX-1 and ICAM-1 expression on aortic vascular endothelium via its antioxidative property.     

Protective effects of daviditin A against endothelial damage induced by lysophosphatidylcholine

Previous investigations have indicated that endogenous inhibitors of nitric oxide synthase (NOS) such as asymmetric dimethylarginine (ADMA) may play an important role in endothelium dysfunction, and some antioxidant drugs improve endothelium function via reduction of ADMA level. The present study examined the antioxidation and endothelial protection of daviditin A, a xanthone compound. Daviditin A significantly inhibited Cu(2+)-induced low-density lipoprotein (LDL) oxidation (EC50: 38.7 microM) and scavenged 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals (EC50: 57.5 microM). Vasodilator responses to acetylcholine in rings of the isolated thoracic aorta were impaired in the presence of lysophosphatidylcholine (LPC)(5 mg/l). Daviditin A (10 or 30 microM) significantly attenuated inhibition by LPC of endothelium-dependent relaxation. Incubation of ECV304 cells with LPC (5 mg/l) for 24 h markedly elevated lactate dehydrogenase (LDH) activity and the levels of malondialdehyde (MDA) and ADMA, and decreased the content of nitric oxide (NO) and the activity of dimethylarginine dimethylaminohydrolase (DDAH). Daviditin A (1, 3 or 10 microM) significantly attenuated the increased release of LDH, increased content of MDA, and decreased level of NO induced by LPC. Daviditin A (3 or 10 microM) significantly inhibited the increased concentration of ADMA. Daviditin A (10 microM) significantly attenuated the decreased activity of DDAH. The present results suggest that daviditin A preserves endothelial dysfunction elicited by LPC, and the protective effect of daviditin A on the endothelium is related to reduction of ADMA concentration.     

Taurine protects against low-density lipoprotein-induced endothelial dysfunction by the DDAH/ADMA pathway

Asymmetric dimethylarginine (ADMA), a major endogenous nitric oxide (NO) synthase inhibitor, is thought to be a key contributor for endothelial dysfunction. Decrease in activity of dimethylarginine dimethylaminohydrolase (DDAH), a major hydrolase of ADMA, causes accumulation of ADMA in some risk factors of atherosclerosis, including hypercholesterolemia. Taurine is a semi-essential amino acid that has previously been shown to have endothelial protective effects. The present study was to test whether the protective effect of taurine on endothelial function is related to modulation of the DDAH/ADMA pathway. A single injection of native LDL (4 mg/kg, i.v.) markedly reduced endothelium-dependent vasorelaxation and the plasma level of NO, and increased plasma concentrations of ADMA, malondialdehyde (MDA) and tumor necrosis factor-alpha (TNF-alpha). Treatment with taurine in vivo (60 or 180 mg/kg) significantly attenuated the inhibition of endothelium-dependent vasorelaxation and the reduced level of NO, and decreased the elevated levels of ADMA, MDA, and TNF-alpha. Incubation human umbilical vein endothelial cells (HUVECs) with ox-LDL (100 microg/ml) for 24 h markedly increased the medium levels of lactate dehydrogenase (LDH), ADMA, TNF-alpha and MDA, and decreased the level of NO in the medium and the intracellular activity of DDAH. Taurine (1 or 5 microg/ml) significantly attenuated the increases in the levels of LDH, ADMA, TNF-alpha and MDA, and the decrease in the level of NO and the activity of DDAH induced by ox-LDL in HUVECs. The present results suggested that taurine protected against endothelial dysfunction induced by native LDL in vivo or by ox-LDL in endothelial cells, and the protective effect of taurine on the endothelium is related to decrease in ADMA level by increasing of DDAH activity.     

Ameliorative effect of astaxanthin on endothelial dysfunction in streptozotocin-induced diabetes in male rats

The present study was designed to examine whether astaxanthin (ASX, 3,3-dihydroxybeta, beta-carotene-4,4-dione, CAS 472-61-7), a dietary antioxidant carotenoid that is naturally present in algae, crustaceans, and fish, has a protective effect on endothelial dysfunction of aortas in diabetic rats and the possible molecular mechanism involved. Male Wistar rats were randomly divided into four groups: control rats, diabetic rats, diabetic rats treated with ASX (10 mg/kg/d), and control rats treated with ASX. Type 1 diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ; 60 mg/ kg). STZ-induced diabetes in rats was complicated with excessive oxidative stress and endothelial dysfunction, increased serum oxidized low-density lipoprotein (ox-LDL) and aortic malondialdehyde (MDA) levels, inhibited endothelium-dependent vasorelaxation to acetylcholine (ACh) and unaffected endothelium-dependent vasorelaxation to sodium nitroprusside (SNP). Simultaneously, lectin-like oxLDL receptor-i (LOX-1) expression was enhanced and endothelial nitric oxide (NO) synthase (eNOS) expression was reduced in the aortas of diabetic rats. ASX treatment could significantly decrease serum oxLDL and aortic MDA levels, attenuate blunted endothelium-dependent vasodilator responses to ACh, upregulate eNOS expression, and decrease LOX-1 expression. These results indicated that ASX could ameliorate diabetic endothelial dysfunction by inhibiting the ox-LDLLOX-1-eNOS pathway. Treatment with ASX might be clinically useful for diabetic complications associated with endothelial dysfunction.     

花卷茶提取物对高胆固醇血症大鼠血脂和内皮功能的影响

目的研究花卷茶提取物对高胆固醇血症大鼠血脂和内皮功能的影响及机制。方法雄性SD大鼠高脂饲养4周诱发高胆固醇血症,其中实验组在高脂饲料饲养2周后开始每日灌胃给予不同剂量的花卷茶系列之十两茶水提物（50、100和200mg.kg-1）,持续2周。实验结束后,颈动脉取血测定血脂、一氧化氮（NO）、非对称二甲基精氨酸（ADMA）和丙二醛（MDA）含量;分离胸主动脉检测血管内皮依赖性舒张功能。结果十两茶提取物能呈剂量依赖性降低高脂血症大鼠血清总胆固醇和低密度脂蛋白及甘油三酯水平。十两茶提取物能显著改善高脂所诱导的血管内皮舒张功能障碍,降低血浆ADMA和MDA含量以及增加NO水平,且呈剂量依赖性。结论花卷茶系列之十两茶提取物具有降低血脂和保护血管内皮功能作用,其作用与抑制脂质过氧化、调节ADMA/NO系统有关。     

糖尿病大鼠内源性ADMA升高与代谢控制的关系

目的　以链脲佐菌素诱导的糖尿病大鼠为实验模型 ,研究内源性一氧化氮合酶 (NOS)抑制物非对称性二甲基精氨酸 (ADMA)升高与糖尿病代谢控制的关系。方法　用高效液相色谱测定大鼠血清ADMA浓度 ;用离体胸主动脉环检测乙酰胆碱诱导的内皮依赖性舒张反应 ;并检测血糖、糖基化血清蛋白和血清脂质过氧化产物丙二醛 (MDA)浓度以反映代谢控制。结果　糖尿病大鼠血清ADMA浓度比正常组大鼠明显升高 ,并伴有离体血管内皮依赖性舒张反应的显著抑制 ;经胰岛素治疗 8wk后 ,不仅阻止内源性ADMA的升高 ,也明显改善血管的内皮依赖性舒张功能。此外 ,糖尿病大鼠血糖、糖基化血清蛋白和血清MDA水平也比正常组明显升高。用胰岛素改善代谢控制后 ,血糖、糖基化血清蛋白和血清MDA水平均恢复正常 ,血中ADMA浓度也显著降低。结论　糖尿病大鼠血中内源性NOS抑制物ADMA浓度升高与代谢控制密切相关 ;胰岛素逆转糖尿病大鼠内源性ADMA升高可能与纠正代谢紊乱和降低脂质过氧化有关     

瑞舒伐他汀与普罗布考抗大鼠动脉粥样硬化机制研究

目的 探讨选择性HMG-COA还原酶抑制剂瑞舒伐他汀(Rosuvastatin)与抗氧化剂普罗布考(Probucol)对大鼠动脉粥样硬化形成的影响,并研究其机制。方法 60只Wistar雄性大鼠,随机分5组,正常饮食组(A组),高脂饮食组(B组),瑞舒伐他汀组(C组),普罗布考组(D组),瑞舒伐他汀联合普罗布考组(E组),每组12只。以高脂饲料喂养加腹腔注射VD₃建立大鼠动脉粥样硬化(AS)模型。第9周,C、D、E组大鼠在高脂喂养基础上给予药物干预。16周末处死各组大鼠,采血检测血脂,酶联免疫吸附法检测血浆氧化低密度脂蛋白(OX-LDL),血清丙二醛(MDA)、超氧化物歧化酶(SOD)、血管内皮细胞钙黏蛋白(VE-cadherin);免疫组织化学法检测主动脉血小板内皮细胞黏附分子1(PECAM-1)的表达;光镜下观察主动脉血管壁病理组织学改变。结果 与A组比较,B、C、D、E组大鼠血清总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白(LDL-C)显著增高(P<0.01),高密度脂蛋白(HDL)降低(P<0.01),OX-LDL、VE-cadherin、MDA升高(P<0.01),而SOD降低(P<0.01),光镜下观察主动脉内膜厚度增加,内膜损害严重,动脉血管PECAM-1表达升高(P<0.01)。与B组比较,C、D、E组大鼠血清TC、LDL-C含量降低(P<0.01),OX-LDL、VE-cadherin、MDA明显下降(P<0.01),SOD升高(P<0.05),光镜下血管内膜较B组薄,内膜损害减轻,PECAM-1表达降低(P<0.01)。与C组比较,D组和E组OX-LDL、MDA降低(P<0.05),SOD升高(P<0.05)。结论 普罗布考降低TC、LDL-C作用,以及抗炎效用与瑞舒伐他汀疗效相似,普罗布考有显著的抗氧化作用,抗氧化疗效优于瑞舒伐他汀,两药合用可减缓AS进展。     

Mechanisms underlying the chronic pravastatin treatment-induced improvement in the impaired endothelium-dependent aortic relaxation seen in streptozotocin-induced diabetic rats

1. We investigated the effects of chronic pravastatin treatment on the impaired endothelium-dependent relaxation seen in aortae from established streptozotocin (STZ)-induced diabetic rats. Starting at 6 weeks of diabetes, pravastatin (10 mg kg(-1)) was administered to STZ-induced diabetic rats for 4 weeks. 2. The increased total cholesterol and low-density lipoprotein (LDL) cholesterol levels seen in STZ-induced diabetic rats were not restored to normal by pravastatin. Aortae from pravastatin-treated diabetic rats did not show an impaired endothelium-dependent relaxation to acetylcholine. The expression of the mRNA for endothelial nitric oxide synthase was unaffected by diabetes or pravastatin. 3. The enhanced level of malondialdehyde (MDA)-modified LDL seen in STZ-induced diabetic rats was normalized by pravastatin treatment. The resistance of LDL to oxidation was assessed by measuring the amount of MDA or conjugated dienes generated by incubation with copper ions. LDL isolated from diabetic rats, but not those from pravastatin-treated diabetics, showed enhanced the susceptibility to oxidation, but incubation in vitro with pravastatin had no effect on LDL oxidation. 4. Following incubation of control aortae for 6 h with LDL (0.1 mg protein ml(-1)) isolated from diabetic rats, the endothelium-dependent relaxation to acetylcholine or A23187 was impaired, but LDL isolated from control or pravastatin-treated rats had no such effect. This inhibitory effect of diabetic LDL was prevented by superoxide dismutase (SOD), a superoxide scavenger. 5. These results suggest that pravastatin preserves endothelial function in aortae from STZ-induced diabetic rats without lowering plasma cholesterol, and its effect may be due to decreased LDL oxidation.     

十两茶提取物抗高脂诱导家兔动脉粥样硬化形成涉及调节ADMA/NO通路

目的：观察十两茶提取物对高脂诱导家兔动脉粥样硬化的影响。方法：家兔高脂饲料喂养4周后,分别灌胃给予不同剂量的十两茶提取物（25、50和100mg/kg）,共4周。实验结束后,颈动脉取血检测红细胞变形能力,测定血脂、NO、非对称二甲基精氨酸（ADMA）和丙二醛（MDA）含量;分离胸主动脉检测脂质斑块面积和血管内皮依赖性舒张功能。结果：十两茶提取物能剂量依赖性地降低高脂饲养家兔血清总胆固醇和低密度脂蛋白水平,同时显著减少主动脉粥样斑块面积和改善血管内皮舒张功能及红细胞变形能力。十两茶提取物显著降低血清MDA和ADMA含量和增加NO水平,且呈剂量依赖性。结论：十两茶提取物具有抗动脉粥样硬化作用,其机制与抑制脂质过氧化、调节ADMA/NO系统,改善血管内皮功能和红细胞变形能力有关。     

Elevated serum endogenous inhibitor of nitric oxide synthase and endothelial dysfunction in aged rats

1. The purpose of the present study was to determine the relationship between endothelial dysfunction and the endogenous inhibitor of nitric oxide synthase NG,NG'-asymmetric dimethylarginine (ADMA) in aged rats. 2. Studies were performed in male adult Sprague-Dawley rats (6 months old; n = 8) and in aged rats (20 months old; n = 8). Serum levels of ADMA and L-arginine were measured by high-performance liquid chromatography and responses of endothelium-intact aortic rings to acetylcholine (ACh) were tested. Nitric oxide synthase activity in kidney tissue and serum concentrations of nitrite, a stable end-product of nitric oxide, were assayed and serum contents of malondialdehyde, derived from lipid peroxidation and serum lipid and creatinine level were determined. 3. Serum levels of ADMA increased significantly in aged rats compared with adult rats (P < 0.01), whereas serum levels of L-arginine were similar in both groups (P = NS). Accordingly, the ratio of L-arginine/ADMA in old rats was lower than that in young rats (P < 0.01). Endothelium-dependent relaxation responses to ACh in aortic rings from aged rats were impaired and these impaired responses were improved by pre-incubation of aortic rings with L-arginine. 4. Nitric oxide synthase activity in the kidney, together with serum concentration of nitrite, was significantly decreased and serum contents of malondialdehyde, cholesterol and triglycerides were increased in old compared with young rats. However, the serum creatinine level was not significantly different between adult and aged rats. 5. Endogenous ADMA may be a contributor to age-related endothelial dysfunction and increases in endogenous ADMA may be linked to lipid peroxidation in aged rats.     

Elevated levels of the serum endogenous inhibitor of nitric oxide synthase and metabolic control in rats with streptozotocin-induced diabetes

This study was designed to determine the relationship between elevated levels of the endogenous inhibitor of nitric oxide synthase, asymmetric dimethylarginine (ADMA), and metabolic control in rats with streptozotocin-induced diabetes. Serum levels of ADMA were measured by high-performance liquid chromatography at 8 weeks after diabetes was induced. Endothelium-dependent relaxation to acetylcholine was tested in aortic rings from nondiabetic age-matched control, untreated diabetic, and insulin-treated diabetic rats to evaluate endothelial function. Serum concentrations of glucose, glycosylated serum protein, and malondialdehyde were examined to estimate metabolic control. Serum levels of ADMA increased dramatically in untreated diabetic rats compared with control rats. This elevation in ADMA levels was accompanied by impairment of the endothelium-dependent relaxation response to acetylcholine in aortic rings. Long-term insulin treatment not only prevented the elevation of serum ADMA levels, but also improved the impairment of endothelium-dependent relaxation in diabetic rats. Serum levels of glucose, glycosylated serum protein, and malondialdehyde were significantly increased in parallel with the elevation of ADMA in untreated diabetic rats compared with control rats. These parameters were normalized after diabetic rats received insulin treatment for 8 weeks. These results provide the first evidence that an elevation in the concentration of ADMA in rats with streptozotocin-induced diabetes is closely related to metabolic control of the disease.     

Mechanism of attenuation of diabetes mellitus and hypercholesterolemia induced vascular endothelial dysfunction by protein tyrosine phosphatase inhibition

The study has been designed to investigate downstream mechanisms in the PTPase inhibition mediated attenuation of diabetes mellitus and hypercholesterolemia-induced vascular endothelial dysfunction. Diabetes mellitus was induced in rats using streptozotocin (55 mg/kg, i.v. once), while hypercholesterolemia was produced by feeding high cholesterol diet. After 4 weeks of streptozotocin and Cholesterol rich diet administration, vascular endothelium dysfunction was assessed, in terms of attenuation of acetylcholine-induced, endothelium-dependent relaxation (Isolated Aortic Ring Preparation), a decrease in serum nitrate/nitrite level, as well as mRNA expression of eNOS (rtPCR) and disruption of integrity of vascular endothelium (Electron microscopy). After 14 days of daily administration, sodium orthovanadate (8 mg/kg, p.o., 16 mg/kg, p.o and 24 mg/kg, p.o) and atorvastatin (30 mg/kg, p.o) (positive control) significantly improved acetylcholine-induced endothelium-dependent relaxation, serum nitrate/nitrite level, mRNA expression of eNOS and maintained integrity of vascular endothelium. However, this ameliorative effect of SOV was significantly blocked by UCN-01, (PDK inhibitor) and L-NAME (Inhibitor of eNOS). Therefore, it may be concluded that sodium orthovanadate, a specific inhibitor of PTPase, may stimulate PDK and eNOS and consequently improve vascular endothelium dysfunction. Thus, inhibition of PTPase might be a useful approach in the therapeutics of vascular endothelium dysfunction.     

Estrogen treatment inhibits vascular endothelial senescence and asymmetrical dimethylarginine in ovariectomized rabbits

To investigate the effects of estrogen treatment on aortic endothelial senescence and atherosclerosis, an ovariectomized female rabbit model was constructed, and human umbilical vein endothelial cells were utilized to explore the potential mechanisms. Twenty-eight female rabbits were randomized into 4 groups (7 each): sham operation, ovariectomized, ovariectomized plus low-dose estradiol treatment, and ovariectomized plus high-dose estradiol treatment. All rabbits were fed on high-cholesterol diet for 12 weeks. Blood samples were collected to determine the serum estradiol, asymmetric dimethyl L-arginine (ADMA), and lipid levels, and the aortas were separated for histopathologic analysis. After ovariectomy and high-fat diet, the concentration of serum estradiols declined significantly (P < 0.01) and the levels of ADMA and serum lipids increased (all P < 0.01) as the area of senescent endothelium and atherosclerotic lesions enlarged (both P < 0.01). However, administration of estradiols reduced the levels of ADMA, total cholesterol, and low-density lipoprotein (LDL) cholesterol and inhibited endothelial senescence and atherosclerosis (all P < 0.01). Simultaneously, the concentration of high-density lipoprotein cholesterol and triglyceride increased (all P < 0.01). In vitro experiments also confirmed that estradiols could decrease the ADMA levels induced by oxidized LDL and inhibited oxidized LDL–induced and ADMA-induced human umbilical vein endothelial cell senescence. These results indicate that estrogens can inhibit endothelial senescence and atherosclerosis with reduced ADMA levels and improved lipid profile.     

Asymmetric dimethylarginine (ADMA) induces vascular endothelium impairment and aggravates post-ischemic ventricular dysfunction in rats

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide (NO) inhibitor recognized as an independent risk factor for endothelial dysfunction and coronary heart diseases. This study investigated whether ADMA (10 mg/kg day for 14 days) affected endothelial function and aggravated post-ischemic ventricular dysfunction in the perfused rat heart. Systolic blood pressure and heart rate, plasma levels of ADMA and nitrite/nitrate were measured in vehicle- and ADMA-treated rats. Perfused hearts were submitted to global ischemia-reperfusion and vascular endothelial dysfunction was examined with angiotensin II in coronary vessels and aortic rings. Endothelial NO synthase (eNOS) and angiotensin-converting enzyme (ACE) mRNA expression in aortic and cardiac tissues were measured. ADMA-treated rats had higher systolic blood pressure (1.3-fold, P<0.01) and slower heart rate (16%, P<0.05) than controls. Plasma ADMA rose (1.9-fold, P<0.01) and nitrite/nitrate concentration decreased 59% (P<0.001). Ventricular contraction (stiffness) increased significantly, with worsening of post-ischemic ventricular dysfunction. In preparations from ADMA-treated rats the coronary vasculature's response to angiotensin II was almost doubled (P<0.01) and the maximal vasorelaxant effect of acetylcholine in aortic rings was significantly lower than in preparations from vehicle-treated rats. In cardiac and aortic tissues eNOS mRNA and ACE mRNA levels were similar in controls and ADMA-treated rats. The increased plasma levels of ADMA presumably cause endothelial dysfunction because of a deficiency in NO production, which also appears involved in the aggravation of myocardial ischemia-reperfusion injury.     

Effect of fenofibrate on the level of asymmetric dimethylarginine in individuals with hypertriglyceridemia

Objective To test whether treatment with fenofibrate decreases asymmetric dimethylarginine (ADMA) level in hypertriglyceridemic individuals. Methods In the present study, 45 subjects with hypertriglyceridemia were recruited to receive treatment with fenofibrate (200 mg/d). Serum concentrations of ADMA, malondialdehyde (MDA), nitric oxide (NO) and tumor necrosis factor-α (TNF-α) were measured. Endothelial function assessed by flow-mediated dilation (FMD) of the brachial artery was performed. Results Compared with control, serum levels of ADMA (0.47±0.05 μmol/L in control and 0.62±0.28 μmol/L in hypertriglyceridemic patients, P<0.01), MDA and TNF-α were markedly elevated, and the level of NO was significantly reduced, concomitantly with impaired endothelium-dependent vasodilation in individuals with hypertriglyceridemia. 8-week treatment with fenofibrate significantly reduced the elevated levels of ADMA (0.53±0.12 μmol/L, P<0.01), MDA and TNF-α, attenuated the decreased level of NO and improved endothelial function. Conclusions These results suggest that the beneficial effect of fenofibrate on the endothelium in hypertriglyceridemic individuals may be related to reduction of ADMA level.     

Effect of phenobarbitone pretreatment upon endothelium-dependent relaxation to acetylcholine in rat superior mesenteric arterial bed.

1. Pretreatment of rats for 5 days with phenobarbitone (80 mg kg-1 day-1) enhanced the potency enhanced the potency of acetylcholine in opposing noradrenaline-induced vasoconstriction in the isolated perfused superior mesenteric arterial bed; in 10 saline-pretreated control animals the ED50 was 14.0 +/- 3.9 ng whereas it was 3.23 +/- 1.00 ng in 10 phenobarbitone-pretreated animals. 2. In both saline- and phenobarbitone-pretreated rats acetylcholine was ineffective at opposing noradrenaline vasoconstriction after the mesentery had been perfused for 90s with a 0.3% solution of the detergent CHAPS in distilled water (to remove the endothelium), but pressor responses to noradrenaline were unaffected. 3. Pretreatment with phenobarbitone had no effect on the opposition by sodium nitroprusside of noradrenaline pressor responses. Also, the effects of nitroprusside were not affected by perfusion with CHAPS in either control or barbiturate-pretreated groups. 4. Inclusion of indomethacin (10 microM) in the perfusion fluid had no effect on the enhancement by phenobarbitone pretreatment of the endothelium-dependent opposition by acetylcholine of noradrenaline pressor responses; the ED50 values in the absence and presence of indomethacin were, respectively, 2.40 +/- 0.31 ng and 1.87 +/- 0.27 ng (n = 6). 5. The concentration of cytochrome P450 in the microsomal fraction obtained from the mesenteric preparation was increased from 204 +/- 32 (saline-pretreated; n = 7) to 784 +/- 249 pmol g-1 wet wt (n = 7) by the phenobarbitone pretreatment. 6. It is concluded that the increase in potency of acetylcholine as an endothelium-dependent vasodilator by phenobarbitone pretreatment is most probably at the level of the endothelium rather than the vascular smooth muscle.