同型半胱氨酸诱导的一氧化氮依赖性血管舒张功能障碍可被超氧化物歧化酶模拟物TEMPOL逆转。

Homocysteine induced impairment of nitric oxide-dependent vasorelaxation is reversible by the superoxide dismutase mimetic TEMPOL.

作者信息

Hucks Davy, Thuraisingham Raj C, Raftery Martin J, Yaqoob Magdi M

机构信息

Experimental Medicine, Nephrology and Critical Care, William Harvey Research Institute, Charterhouse Square, St Bartholomew's and the Royal London Hospitals, Queen Mary, University of London, London EC1M 6BQ, UK.

出版信息

Nephrol Dial Transplant. 2004 Aug;19(8):1999-2005. doi: 10.1093/ndt/gfh270.

DOI:10.1093/ndt/gfh270

PMID:15252169

Abstract

BACKGROUND

Elevated plasma homocysteine concentrations in renal patients are associated with accelerated cardiovascular disease. The mechanism(s) by which homocysteine acts remains unclear however, evidence implicates a role involving endothelial dysfunction.

METHODS

Rat femoral arteries after acute or 4-h pre-incubation with racemic D,L-homocysteine (100 microM) were mounted on a myograph, pre-constricted with phenylephrine (10 microM) and responses to acetylcholine-dependent vasorelaxation examined. The incubations were repeated in the presence of indomethacin (10 microM), omega-nitro-L-arginine methyl ester (100 microM), L-arginine (100 microM), tetrahydrobiopterin (1 microM), catalase (1200 U/ml), ebselen, a peroxynitrite chelator (20 microM) and TEMPOL, a superoxide dismutase mimetic (1 mM). Results are shown as means+/-standard error, expressed as per cent relaxation to acetylcholine added (nmol/l).

RESULTS

Increasing concentrations of homocysteine had no affect when added directly to basally relaxed or pre-constricted freshly isolated vessels. However, 4-h pre-incubation with or without homocysteine significantly shifted the acetylcholine EC(50) (EC(50) was defined as the concentration of acetylcholine that caused relaxation of the phenylephrine contracted tissue by 50%), control((4 h)) = 74.7 nmol/l+/-10.5 vs 100 microM D,L-homocysteine((4 h)) = 159.9 nmol/l+/-20.6; P<0.05) without affecting maximal relaxation. Response to endothelial independent relaxation was unaffected. Indomethacin, indomethacin and omega-nitro-L-arginine methyl ester, l-arginine and tetrahydrobiopterin, catalase and ebselen had no effect on the EC(50) in homocysteine-exposed arteries. However, TEMPOL normalized vasorelaxation in homocysteine-treated arteries (75.2 nmol/l+/-14.6) but had no effect on the 4-h control group. Moreover, washing TEMPOL from the treated vessels restored endothelial dysfunction in D,L-homocysteine-treated vessels (163.9 nmol/l+/-34.1).

CONCLUSIONS

We conclude that homocysteine causes endothelial dysfunction by up-regulating a potential superoxide generating system resulting in reduced nitric oxide bio-availability.

摘要

背景

肾病患者血浆同型半胱氨酸浓度升高与心血管疾病加速有关。然而，同型半胱氨酸发挥作用的机制尚不清楚，有证据表明其作用涉及内皮功能障碍。

方法

将大鼠股动脉在体外血管环张力测定仪上安装好，先用去氧肾上腺素（10μM）预收缩，然后分别加入不同物质进行孵育。孵育分为急性孵育或4小时预孵育，加入外消旋D，L-同型半胱氨酸（100μM）。之后检测对乙酰胆碱依赖性血管舒张的反应。孵育在吲哚美辛（10μM）、ω-硝基-L-精氨酸甲酯（100μM）、L-精氨酸（100μM）、四氢生物蝶呤（1μM）、过氧化氢酶（1200U/ml）、依布硒仑（一种过氧亚硝酸盐螯合剂，20μM）和TEMPOL（一种超氧化物歧化酶模拟物，1mM）存在的情况下重复进行。结果以平均值±标准误表示，以加入乙酰胆碱后（nmol/l）的舒张百分比表示。

结果

直接向基础舒张或预收缩的新鲜分离血管中加入不同浓度的同型半胱氨酸均无影响。然而，无论有无同型半胱氨酸进行4小时预孵育，均显著改变了乙酰胆碱的半数有效浓度（EC50，EC50定义为使去氧肾上腺素收缩的组织舒张50%时的乙酰胆碱浓度），对照组（4小时）=74.7nmol/l±10.5，而100μM D，L-同型半胱氨酸（4小时）=159.9nmol/l±20.6；P<0.05），但不影响最大舒张。对内皮非依赖性舒张的反应未受影响。吲哚美辛、吲哚美辛和ω-硝基-L-精氨酸甲酯、L-精氨酸和四氢生物蝶呤、过氧化氢酶和依布硒仑对同型半胱氨酸处理的动脉中的EC50无影响。然而，TEMPOL使同型半胱氨酸处理的动脉中的血管舒张恢复正常（75.2nmol/l±14.6），但对4小时对照组无影响。此外，从处理过的血管中洗去TEMPOL可使D，L-同型半胱氨酸处理的血管中的内皮功能障碍恢复（163.9nmol/l±34.1）。