Sesamin exerts renoprotective effects by enhancing NO bioactivity in renovascular hypertensive rats fed with high-fat-sucrose diet

In the present study, we aimed to evaluate the protective effect of sesamin on kidney damage and renal endothelial dysfunction in two-kidney, one-clip renovascular hypertensive rats fed with a high-fat-sucrose diet (2K1C rats on HFS diet). Sesamin was intragastrically administered to 2K1C rats on HFS diet for eight weeks. Then, we measured the levels of serum hydrogen peroxide (H?O?), total antioxidant capability (T-AOC), renal malonaldehyde (MDA), total-erythrocuprein (T-SOD) and glutathione peroxidase (GSH-P(X)). The expressions of endothelial nitric oxide synthase (eNOS), nitrotyrosine and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47(phox) in the left and right renal cortexes were detected by Western blotting. Pathological changes in the left and right renal cortexes were observed by periodic acid-schiff staining (PAS) and Masson's staining. Treatment with sesamin (120 and 60mg/kg?1·d?1) in 2K1C rats on HFS diet improved renal function, corrected structural abnormalities, and attenuated renal oxidative stress. Furthermore, sesamin increased eNOS protein expression and reduced nitrotyrosine and p47phox protein expression. These results demonstrated that long-term treatment with sesamin had renoprotective effect and improved renal endothelial dysfunction via upregulation of eNOS expression and reduction of NO oxidative inactivation in both clipped and contralateral kidneys of 2K1C rats on HFS diet, and sesamin may have a favorably therapeutic value in treating chronic kidney disease in patients with hypertension and hyperlipemia.     

芝麻素对2型糖尿病大鼠主动脉内皮功能的保护作用

目的探讨芝麻素改善2型糖尿病大鼠主动脉内皮功能损伤的作用及可能机制。方法采用长期高脂饮食加小剂量链脲佐菌素(streptozotocin,STZ)建立2型糖尿病大鼠模型。灌服不同剂量芝麻素(120、60 mg.kg-1.d-1)8周后处死动物。离体血管灌流法测大鼠主动脉内皮依赖性舒张反应及NO生物活性,测血清丙二醛(malondialdehyde,MDA)含量和总抗氧化能力(total antioxidative capacity,T-AOC),Western blot测主动脉内皮型一氧化氮合酶(endothelial nitricoxide synthase,eNOS)、硝基酪氨酸(nitrotyrosine,NT)和还原型辅酶Ⅱ(NADPH)氧化酶亚基P47phox蛋白表达。结果与模型组相比,芝麻素(120 mg.kg-1.d-1)组内皮依赖性血管舒张功能增强,NO活性升高;血清MDA含量降低,T-AOC水平升高;主动脉eNOS蛋白表达增高,NT和P47phox蛋白表达降低。结论芝麻素可改善糖尿病大鼠血管内皮功能,其机制与上调血管eNOS表达和减轻NO氧化失活有关。     

芝麻素与维生素E联用对代谢综合征大鼠肾病的协同保护作用

目的：观察芝麻素与维生素E联用对代谢综合征大鼠肾脏的保护作用并探讨两药联用的协同关系。方法：采用高脂高糖饮食24周诱导大鼠代谢综合征,第9周（57 d）口服含芝麻素（30 mg.kg^-1.d^-1）、芝麻素＋维生素E[（30＋20）、（15＋20）mg.kg^-1.d^-1]和维生素E（20mg.kg^-1.d^-1）饲料16周。24周末称体重和左肾湿重;测血糖、血脂、血压、肾功能、肾皮质氧化和抗氧化指标;HE和Masson染色观察肾脏形态及胶原沉积;免疫组化法表达诱导型一氧化氮合酶和硝基酪氨酸。结果：（1）模型组肾功能明显损害,肾小球发生硬化和肾间质纤维化,并出现大量炎症细胞浸润,肾小球和肾间质胶原沉积,脂质过氧化物损伤因子MDA、NO2-/NO3-和OH-含量升高,iNOS蛋白和硝基酪氨酸表达明显上调,抗氧化酶保护因子T-SOD、CAT、GSH-Px活性显著降低;（2）芝麻素＋维生素E[（30＋20 mg/kg）]组能明显降低血糖、血脂和血压,提高肾皮质总超氧化物歧化酶、过氧化氢酶、谷胱甘肽过氧化酶活性,减少丙二醛、NO2^-/NO3^-和羟自由基含量,下调诱导型一氧化氮合酶和硝基酪氨酸,减轻肾小球与肾间质胶原沉积,逆转肾小球硬化和肾间质纤维化,改善肾功能,并且优于单用芝麻素组和维生素E组（P〈0.01或P〈0.05）。结论：芝麻素（30 mg/kg）与维生素E（20 mg/kg）联用具有协同抗氧化和抗代谢综合征大鼠肾脏损伤作用。     

Sesamin ameliorates arterial dysfunction in spontaneously hypertensive rats via downregulation of NADPH oxidase subunits and upregulation of eNOS expression

Aim:

Sesamin is one of the major lignans in sesame seeds with antihyperlipidemic, antioxidative and antihypertensive activities. The aim of this study was to examine the effects of sesamin on arterial function in spontaneously hypertensive rats (SHRs).

Methods:

SHRs were orally administered sesamin (40, 80 and 160 mg·kg⁻¹·d⁻¹) for 16 weeks. After the rats were killed, thoracic aortas were dissected out. The vasorelaxation responses of aortic rings to ACh and nitroprusside were measured. The expression of eNOS and NADPH oxidase subunits p47^phox and p22^phox in aortas were detected using Western blotting and immunohistochemistry. Aortic nitrotyrosine was measured with ELISA. The total antioxidant capacity (T-AOC) and MDA levels in aortas were also determined.

Results:

The aortic rings of SHRs showed significantly smaller ACh-induced and nitroprusside-induced relaxation than those of control rats. Treatment of SHRs with sesamin increased both the endothelium-dependent and endothelium-independent relaxation of aortic rings in a dose-dependent manner. In aortas of SHRs, the level of T-AOC and the expression of nitrotyrosine, p22^phox and p47^phox proteins were markedly increased, while the level of MDA and the expression of eNOS protein were significantly decreased. Treatment of SHRs with sesamin dose-dependently reversed these biochemical and molecular abnormalities in aortas.

Conclusion:

Long-term treatment with sesamin improves arterial function in SHR through the upregulation of eNOS expression and downregulation of p22^phox and p47^phox expression.     

Resveratrol prevents endothelial nitric oxide synthase uncoupling and attenuates development of hypertension in spontaneously hypertensive rats

Endothelial dysfunction is a hallmark of hypertension and vascular oxidative stress can contribute to endothelial dysfunction and hypertension development. Resveratrol is an antioxidant polyphenol which improves endothelium dependent relaxation, the mechanisms of which are unknown. Also, the role of resveratrol in hypertension remains to be established. The purpose of this study was to investigate the mechanisms of resveratrol induced improvement of endothelial function and establish its role in hypertension. SHR and WKY rats, 3-4 weeks old, were treated with resveratrol in drinking water for 10 weeks, untreated SHR and WKY rats served as controls. At the end of the treatment, control SHR exhibited increased blood pressure, oxidative stress and attenuated endothelium dependent relaxation in comparison to WKY rats. The impaired endothelium function in SHR was associated with lower nitrite/nitrate levels, elevated nitrotyrosine content and eNOS uncoupling. Resveratrol treatment attenuated hypertension development in SHR as indicated by lower blood pressure in resveratrol treated SHR (SHR-R) compared to control SHR. SHR-R also exhibited reduced H(2)O(2) content and elevated superoxide dismutase activity. Resveratrol treatment normalized endothelium dependent vasorelaxation in SHR. In parallel, resveratrol restored nitrite/nitrate levels and normalized nitrotyrosine content in SHR. SHR exhibited increased l-arginine dependent superoxide production which was blocked by NOS inhibitor l-NNA, suggesting eNOS uncoupling. eNOS uncoupling was prevented by resveratrol treatment. In conclusion, early treatment with resveratrol lowers oxidative stress, preserves endothelial function and attenuates development of hypertension in SHR. More importantly, prevention of eNOS uncoupling and NO scavenging could represent novel mechanisms for resveratrol-mediated antihypertensive effects.     

芝麻素与维生素E联用对代谢综合征

目的:观察芝麻素与维生素E联用对代谢综合征大鼠肾脏的保护作用并探讨两药联用的协同关系.方法:采用高脂高糖饮食24周诱导大鼠代谢综合征,第9周(57 d)口服含芝麻素(30 mg·kg~(-1)·d~(-1))、芝麻素+维生素E[(30+20)、(15+20)mg·kg~(-1)·d~(-1)]和维生素E(20mg·kg~(-1)·d~(-1))饲料16周.24周末称体重和左肾湿重;测血糖、血脂、血压、肾功能、肾皮质氧化和抗氧化指标;HE和Masson染色观察肾脏形态及胶原沉积;免疫组化法表达诱导型一氧化氮合酶和硝基酪氨酸.结果:(1)模型组肾功能明显损害,肾小球发生硬化和肾间质纤维化,并出现大量炎症细胞浸润,肾小球和肾间质胶原沉积,脂质过氧化物损伤因子MDA、NO_2~-/NO_3~-和OH~-含量升高,iNOS蛋白和硝基酪氨酸表达明显上调,抗氧化酶保护因子T-SOD、CAT、GSH-Px活性显著降低;(2)芝麻素+维生素E[(30+20mg/kg)]组能明显降低血糖、血脂和血压,提高肾皮质总超氧化物歧化酶、过氧化氢酶、谷胱甘肽过氧化酶活性,减少丙二醛、NO_2~-/NO_3~-和羟自由基含量,下调诱导型一氧化氮合酶和硝基酪氨酸,减轻肾小球与肾间质胶原沉积,逆转肾小球硬化和肾间质纤维化,改善肾功能,并且优于单用芝麻素组和维生素E组(P＜0.01或P＜0.05).结论:芝麻素(30 mg/kg)与维生素E(20 mg/kg)联用具有协同抗氧化和抗代谢综合征大鼠肾脏损伤作用.     

芝麻素的抗氧化作用及其对代谢综合征大鼠肾病的影响

目的探讨芝麻素(sesamin,Ses)对代谢综合征大鼠肾病的影响。方法高脂、高糖诱导大鼠代谢综合征24wk,第9周口服含药芝麻素(120、60、30mg·kg-1.d-1)和辛伐他汀(5mg·kg-1.d-1)16wk,称体重和左肾湿重;测血糖、血脂、血压、肾功能、肾皮质氧化和抗氧化指标;HE和Masson染色观察肾脏形态及胶原沉积;免疫组化法表达诱导型一氧化氮合酶和硝基酪氨酸。结果芝麻素高中剂量组能明显降低代谢综合征大鼠血糖、血脂和血压,提高肾皮质总超氧化物歧化酶、过氧化氢酶、谷胱甘肽过氧化酶活性,减少丙二醛、NO2-/NO3-和羟自由基含量,下调诱导型一氧化氮合酶和硝基酪氨酸,减轻肾小球与肾间质胶原沉积,逆转肾小球硬化和肾间质纤维化,改善肾功能。结论芝麻素具有抗氧化应激和改善代谢综合征肾病的作用。     

Apocynin reduces blood pressure and restores the proper function of vascular endothelium in SHR

This study has evaluated how the vascular endothelium of hypertensive rats chronically treated with apocynin affects acetylcholine (ACh), sodium nitroprusside (SNP), and phenylephrine (PE) action on the nitric oxide (NO) signal transduction pathway in endothelial (EC) and vascular smooth muscle cells. Treatment with apocynin significantly reduced the mean arterial pressure in spontaneously hypertensive rats (SHR). In addition, apocynin improved the impaired ACh hypotensive effect on SHR. Although systemic oxidative stress was high in SHR, SHR treated with apocynin and normotensive rats presented similar systemic oxidative stress levels. Endothelium significantly blunted PE contractions in intact aortas of treated SHR. The ACh effect was impaired in resistance arteries and aortas of SHR, but this same effect was improved in treated SHR. The SNP potency was higher in intact resistance arteries of treated SHR than in intact resistance arteries of untreated SHR. NO and calcium concentrations increased, whereas reactive oxygen species levels decreased in EC of treated SHR. Aortas of untreated and treated SHR did not differ in terms of sGC alpha or beta units expression. Aorta of treated SHR expressed higher eNOS levels as compared to aorta of untreated SHR. The study groups did not differ with respect to NOX1, NOXO1, or NOX4 expression. However, treatment with apocynin normalized overexpression of NOX2 and its subunit p47phox in aortas of SHR. Based on all the results presented in this study, we suggest apocynin increases NO biovailability by different mechanisms, restoring the proper function of vascular endothelium in SHR.     

NADPH氧化酶对自发性高血压大鼠体内氧化应激的影响

目的考察NADPH氧化酶对自发性高血压大鼠体内氧化应激的影响。方法22wk龄自发性高血压大鼠(SHR)和正常血压WKY大鼠,采用尾套法测定血压,Greiss反应测定血清一氧化氮分泌量,ABTS和FRAP法进行血清总抗氧化能力测定,血管环舒缩测定来评价超氧阴离子清除剂超氧化物歧化酶(SOD)和NADPH氧化酶抑制剂夹竹桃麻素(Apo)对大鼠腹主动脉内皮依赖性舒张反应;采用RT-PCR考察内皮型一氧化氮合酶(eNOS)、NADPH氧化酶亚基p22phox以及NADPH氧化酶亚基gp91phox类似物nox4mRNA表达。结果与WKY大鼠相比,SHR血压升高,而血清总抗氧化水平及NO分泌量均降低。PCR显示SHR胸主动脉中eNOS及p22phoxmRNA表达与WKY大鼠相比差异无显著性,而nox4表达则升高。SHR腹主动脉内皮依赖性舒张反应与WKY相比降低,SOD或Apo均能明显逆转该变化。结论结果提示SHR体内氧化应激状态与NADPH氧化酶gp91phox类似物nox4mRNA过表达有关;NADPH氧化酶依赖性的氧化应激参与了SHR内皮功能障碍的发生发展;药理调节NADPH氧化酶功能或应用抗氧化治疗可明显改善SHR内皮依赖性舒张反应。     

芝麻素对自发性高血压大鼠肾病的保护作用

目的:观察芝麻素对自发性高血压大鼠(SHR)肾病的保护作用。方法:SHR灌胃芝麻素(160、80、40mg/kg)16周,每日一次。测定动物给药前后血压及给药后血Cr和BUN含量;HE染色观察肾小球病理变化;MASSON染色观察肾小球和肾间质胶原纤维变化;透射电镜观察肾小球超微结构。结果:芝麻素(160mg/kg)给药16周,能明显降低大鼠的血压、血Cr和BUN含量;改善肾小球变形、萎缩、硬化甚至玻璃样变等病理改变;肾小球系膜区未见明显扩大,基底膜未增厚,足突细胞无明显融合;肾小管细胞损伤和间质纤维化明显减轻。结论:芝麻素具有改善肾功能、保护肾脏作用。     

Effect of cross-fostering on renal anti-oxidant/oxidant status and development of hypertension in spontaneously hypertensive rats

1. The hypotensive effect of cross-fostering in spontaneously hypertensive rats (SHR) is thought to involve adjustments in renal function. However, its association with renal anti-oxidant/oxidant balance during cross-fostering is not known. 2. The present study examined the effect of cross-fostering and in-fostering of 1-day-old offspring between SHR and Wistar-Kyoto (WKY) dams on renal anti-oxidant/oxidant status and systolic blood pressure (SBP). Renal anti-oxidant/oxidant status and SBP were determined in the offspring from 4-16 weeks of age. 3. Cross-fostered SHR had significantly lower SBP than in-fostered SHR at 6, 8 and 12 weeks, but not at 16 weeks (127 ± 1 vs 144 ± 2, 138 ± 1 vs 160 ± 1, 174 ± 2 vs 184 ± 2 and 199 ± 2 vs 194 ± 3 mmHg at 6, 8, 12 and 16 weeks, respectively). No differences in SBP were evident between cross-fostered and in-fostered WKY rats. There were no significant differences in levels of thiobarbituric acid-reactive substances (TBARS), protein carbonyl and total anti-oxidant status (TAS) or superoxide dismutase, catalase, glutathione peroxidase (GPx), glutathione S-transferase and glutathione reductase activity between cross-fostered and in-fostered SHR or WKY offspring. However, compared with WKY rats, catalase activity was higher at 6 and 16 weeks, TAS was higher at 16 weeks and GPx activity and TBARS were lower at 16 weeks in SHR. 4. It appears that cross-fostering of SHR offspring to WKY dams during the early postnatal period causes a transient delay in the rise in blood pressure in SHR and that this does not involve the renal anti-oxidant/oxidant system.     

替米沙坦对高血压大鼠血管ACE2表达及氧化应激水平的影响

目的探讨替米沙坦干预对自发性高血压大鼠(SHR)血管组织血管紧张素转换酶2(ACE2)基因表达、一氧化氮(NO)及氧化应激水平的影响。方法选取10周龄SHR及其同源对照WKY大鼠,分别给予替米沙坦(5、10 mg.kg-1.d-1)或安慰剂,为期10周。采用Western blot检测治疗后大鼠主动脉组织中ACE2蛋白及内皮型NO合酶(eNOS)磷酸化水平。分别采用硝酸还原酶比色法与硫代巴比妥酸比色法测定大鼠主动脉组织中NO和丙二醛(MDA)含量。结果与WKY对照组相比,SHR大鼠主动脉组织中ACE2蛋白和Ser1177-eNOS磷酸化水平明显降低(ACE2:0.39±0.05vs 1.00±0.06;p-eNOS:0.43±0.06 vs 1.00±0.04;P值均<0.01),伴NO水平下调及MDA含量增加(NO mmol.g-1protein:11.5±2.1 vs 27.8±4.9;MDA nmol.g-1 protein:393.9±17.9 vs 186.3±14.5;P值均<0.01),而经替米沙坦治疗后SHR低、高剂量治疗组大鼠主动脉组织中ACE2蛋白和Ser1177-eNOS磷酸化水平增加(ACE2:0.62±0.06,0.65±0.07 vs 0.39±0.05;p-eNOS:0.68±0.07,0.71±0.06 vs0.43±0.06;P值均<0.05),伴NO水平升高(19.2±3.3,23.9±3.2 vs 11.5±2.1 mmol.g-1protein;P值均<0.05)与MDA含量下调(271.9±16.1,249.2±19.6 vs 393.9±17.9nmol.g-1protein;P值均<0.05)。结论长期替米沙坦治疗通过提升高血压大鼠血管ACE2表达及eNOS磷酸化水平,可促使血管NO生成及氧化应激水平改善,提示替米沙坦对高血压具有一定的血管保护功效。     

Effect of nebivolol on endothelial nitric oxide and peroxynitrite release in hypertensive animals: Role of antioxidant activity

We tested the activity of nebivolol, a beta1-selective blocker with respect to nitric oxide (NO) and peroxynitrite (ONOO) generation in the endothelium of normotensive Wistar Kyoto (WKY rats) and spontaneously hypertensive rats (SHR). The endothelial effects of nebivolol and its 2 optical enantiomers were correlated with its antioxidant activity and compared to another beta-blocker, atenolol, and 2 agonists of nitric oxide synthase (eNOS), calcium ionophore (CI) and acetylcholine (ACh). The effects of nebivolol on the bioavailability of NO and ONOO, indicators of endothelial function and dysfunction, respectively, were measured in vitro using nanosensors placed in mesenteric arteries. Compared with WKY rats, treatment of SHR vessels either with ACh (1 micromol/L) or CI (1 micromol/L) showed marked deficiencies (>40%, P < 0.01) in bioavailable NO concomitant with increased ONOO levels (>50%, P < 0.01). The [NO]/[ONOO] ratio measured after stimulation with CI was 2.77 +/- 0.05 in WKY rats and much lower (1.14 +/- 0.11) in SHR indicating significant eNOS uncoupling and endothelial dysfunction in hypertensive animals. Treatment with nebivolol (10 micromol/L) inhibited eNOS uncoupling and reduced endothelial dysfunction in SHR, as evidenced by an increase in the [NO]/[ONOO] ratio to 3.09 +/- 0.04. The basis for nebivolol activity is attributed to its unique membrane interactions as determined by small-angle x-ray diffraction, as well as its antioxidant activity at nanomolar to micromolar levels. The antioxidant effects of nebivolol and its enantiomers were not reproduced by atenolol. These results demonstrate that nebivolol inhibits endothelial dysfunction through a potent antioxidant mechanism attributed to its physicochemical interactions with the membrane, independent of beta1-blockade activity.     

Genistein ameliorated endothelial nitric oxidase synthase uncoupling by stimulating sirtuin-1 pathway in ox-LDL-injured HUVECs

Endothelial nitric oxidase synthase (eNOS) uncoupling plays a causal role in endothelial dysfunction in atherosclerosis. Genistein consumption has been associated with the prevention of atherosclerosis. However, the effect of genistein on eNOS uncoupling has not been reported. A model of oxidized low-density lipoprotein (ox-LDL)-induced injury on human umbilical vein endothelial cells (HUVECs) was established to evaluate the effect of genistein on eNOS uncoupling. We investigated the effect of genistein on NADPH oxidase-dependent superoxide production, NOX4 expression, BH4 synthesis and oxidation, the expression of GTP cyclohydrolase 1 (GCH1) and dihydrofolate reductase (DHFR). The results showed that genistein decreased superoxide production and NOX4 expression, enhanced the ratio of BH4/BH2, augmented the expressions of GCH1 and DHFR. Accompanied with genistein ameliorating eNOS uncoupling, genistein elevated the expression of sirtuin-1; furthermore, the effects of genistein on eNOS uncoupling were blunted with sirtuin-1 siRNA. The present study indicated that genistein ameliorated eNOS uncoupling was concerned with sirtuin-1 pathway in ox-LDL-injured HUVECs.     

Pyridoxine inhibits endothelial NOS uncoupling induced by oxidized low-density lipoprotein via the PKCα signalling pathway in human umbilical vein endothelial cells

BACKGROUND AND PURPOSE

One key mechanism for endothelial dysfunction is endothelial NOS (eNOS) uncoupling, whereby eNOS generates superoxide (O₂^•−) rather than NO. We explored the effect of pyridoxine on eNOS uncoupling induced by oxidized low-density lipoprotein (ox-LDL) in human umbilical vein endothelial cells (HUVECs) and the potential molecular mechanism.

EXPERIMENTAL APPROACH

HUVECs were incubated with ox-LDL with/without pyridoxine, N^G-nitro-L-arginine methylester (L-NAME), chelerythrine chloride (CHCI) or apocynin. Endothelial O₂^•− was measured using lucigenin chemiluminescence, and O₂^•−-sensitive fluorescent dye dihydroethidium (DHE). NO levels were measured by chemiluminescence, PepTag Assay for non-radioactive detection of PKC activity, depletion of PKCα and p47phox by siRNA silencing and the states of phospho-eNOS Thr495, total-eNOS, phospho-PKCα/βII, total PKC, phospho-PKCα, total PKCα and p47phox were measured by Western blot.

KEY RESULTS

Ox-LDL significantly increased O₂^•− production and reduced NO levels released from HUVECs; an effect reversed by eNOS inhibitor, L-NAME. Pyridoxine pretreatment significantly inhibited ox-LDL-induced O₂^•− generation and preserved NO levels. Pyridoxine also prevented the ox-LDL-induced reduction in phospho-eNOS Thr495 and PKC activity. These protective effects of pyridoxine were abolished by the PKC inhibitor, CHCI, or siRNA silencing of PKCα. However, depletion of p47phox or treatment with the NADPH oxidase inhibitor, apocynin, had no influence on these effects. Also, cytosol p47phox expression was unchanged by the different treatments.

CONCLUSIONS AND IMPLICATIONS

Pyridoxine mitigated eNOS uncoupling induced by ox-LDL. This protectant effect was related to phosphorylation of eNOS Thr495 stimulated by PKCα, not via NADPH oxidase. These results provide support for the use of pyridoxine in ox-LDL-related vascular endothelial dysfunction.     

普罗布考对心脏微血管内皮细胞eNOS脱耦联与NADPH氧化应激途径的影响

目的观察普罗布考对心脏微血管内皮细胞内内皮型一氧化氮合酶（eNOS）脱耦联的作用,探讨其作用机制。方法100 mg&#8226;L－1牛血清清蛋白糖基化终末产物（BSA AGEs）与5,10,20 μmol&#8226;L－1普罗布考作用于心脏微血管内皮细胞24 h,检测四氢生物喋呤（BH4）、一氧化氮（NO）和超氧阴离子（O2 ）,免疫组织化学检测eNOS蛋白表达情况,荧光染色检测活性氧簇（ROS）,Western blot检测p47phox蛋白。结果随着普罗布考浓度增加,NO生成增加,O2 生成减少,eNOS表达减少,BH4含量增加,ROS表达降低,p47phox表达减少（P＜0.01或P＜0.05）。结论普罗布考能抑制AGEs诱导的心脏微血管内皮细胞eNOS脱耦联,其机制可能与抑制NADPH氧化应激有关。     

Endothelial NO synthase as a source of NO and superoxide

Endothelial nitric oxide (NO) synthase (eNOS) is responsible for most of the vascular NO produced. A functional eNOS transfers electrons from nicotinamide adenine dinucleotide phosphate (NADPH) via flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) in the carboxy-terminal reductase domain to the heme in the amino-terminal oxygenase domain where the substrate L-arginine is oxidized to L-citrulline and NO. This normal flow of electrons requires dimerization of the enzyme, the presence of the substrate L-arginine, and presence of the cofactor (6R)-5,6,7,8-tetrahydro-L-biopterin (BH₄), one of the most potent naturally occurring reducing agents. Cardiovascular risk factors, such as hypertension, hypercholesterolemia, diabetes mellitus, or chronic smoking, stimulate the production of reactive oxygen species (ROS) in the vascular wall. NADPH oxidases represent major sources of this ROS and have been found upregulated in animal models of hypertension, diabetes, and sedentary lifestyle. Superoxide avidly interacts with vascular NO to form peroxynitrite (ONOO⁻). BH₄ is highly sensitive to oxidation, e.g., by ONOO⁻, and reduced levels of BH₄ promote eNOS uncoupling. In fact, in many cases, supplementation with BH₄ is capable of correcting eNOS dysfunction. Alternatively, an oxidation of the zinc-thiolate complex of eNOS by ONOO⁻ has been proposed as a mechanism for eNOS uncoupling. Under uncoupled conditions, superoxide is generated from the oxygenase domain of eNOS. eNOS uncoupling and its change from a protective enzyme to a contributor to oxidative stress has been observed in several in vitro models and in animals with cardiovascular pathophysiology such as spontaneously hypertensive rats (SHR), angiotensin-II-induced hypertension, or diabetes. Taken together, several mechanisms seem to underlie endothelial dysfunction, but an uncoupled eNOS markedly contributes to this phenomenon.

     

Downregulation of vascular soluble guanylate cyclase induced by high salt intake in spontaneously hypertensive rats

1. Cyclic guanosine monophosphate (cyclic GMP)-mediated mechanism plays an important role in vasodilatation and blood pressure regulation. We investigated the effects of high salt intake on the nitric oxide (NO) - cyclic GMP signal transduction pathway regulating relaxation in aortas of spontaneously hypertensive rats (SHR). 2. Four-week-old SHR and normotensive Wistar-Kyoto rats (WKY) received a normal salt diet (0.3% NaCl) or a high salt diet (8% NaCl) for 4 weeks. 3. In aortic rings from SHR, endothelium-dependent relaxations in response to acetylcholine (ACh), adenosine diphosphate (ADP) and calcium ionophore A23187 were significantly impaired by the high salt intake. The endothelium-independent relaxations in response to sodium nitroprusside (SNP) and nitroglycerin were also impaired, but that to 8-bromo-cyclic GMP remained unchanged. On the other hand, high salt diet had no significant effects on the relaxations of aortic rings from WKY. 4. In aortas from SHR, the release of NO stimulated by ACh was significantly enhanced, whereas the production of cyclic GMP induced by either ACh or SNP was decreased by the high salt intake. 5. Western blot analysis showed that the protein level of endothelial NO synthase (eNOS) was slightly increased, whereas that of soluble guanylate cyclase (sGC) was dramatically reduced by the high salt intake. 6. These results indicate that in SHR, excessive dietary salt can result in downregulation of sGC followed by decreased cyclic GMP production, which leads to impairment of vascular relaxation in responses to NO. It is notable that chronic high salt intake impairs the sGC/cyclic GMP pathway but not the eNOS/NO pathway.     

Effect of chronic apocynin treatment on nitric oxide and reactive oxygen species production in borderline and spontaneous hypertension

The purpose of this study was to investigate the effect of NAD(P)H oxidase inhibitor – apocynin (4-hydroxy-3-methoxyacetophenone) on the increase of systolic blood pressure (SBP) in borderline (BHR) and spontaneously hypertensive rats (SHR). Young 6-week-old male BHR (offspring of SHR dams andWistar Kyoto sires) and SHR were treated with apocynin (30 mg/kg/day) for six weeks. SBP was measured by tail-cuff plethysmography. Nitric oxide synthase (NOS) activity was determined in the left ventricle and aorta. Protein expression of nuclear factor kappa B (NF-κB) and NAD(P)H oxidase subunits p67phox and p22phox as well as concentration of cGMPwere determined for the left ventricle. Apocynin significantly decreased SBP in all groups investigated. Administration of apocynin had no effect on NOS activity in either tissue studied. However, apocynin decreased protein expression of NF-κB (p65) and NAD(P)H oxidase subunit p22phox in both hypertensive groups and p67phox subunit in the SHR group. Moreover, apocynin was able to prevent a decrease in cGMP concentration in the left ventricle of both hypertensive groups. In conclusion, our study demonstrated that apocynin treatment partially prevented SBP rise in borderline and spontaneously hypertensive rats, yet without increasing activity of NOS in the left ventricle and aorta. However, apocynin was able to decrease production of reactive oxygen species in hypertensive rats; thus preventing the decrease in cGMP formation.