Hydrogen peroxide-induced impairment of reactivity in rat isolated aorta: potentiation by 3-amino-1,2,4-triazole

1. In this study the impairment induced by hydrogen peroxide of vascular reactivity and the role of endogenous catalase in protection against this impairment was assessed in isolated rings of rat aorta.
2. Incubation with hydrogen peroxide at 1 mM, but not at 0.1 mM, for 15, 30 or 60 min followed by washout depressed, in a time-dependent manner, the subsequent ability of endothelium-containing and endothelium-denuded rings to contract to phenylephrine.
3. Incubation with 3-amino-1,2,4-triazole (50 mM, 90 min, followed by washout) to inhibit endogenous catalase had no effect by itself on subsequent phenylephrine-induced contraction. However, pretreatment with 3-amino-1,2,4-triazole did lead to a profound enhancement of the ability of hydrogen peroxide (1 mM, present for the final 30 min of the 90 min incubation, followed by washout) to depress phenylephrine-induced contraction in both endothelium-containing and endothelium-denuded rings.
4. Incubation with hydrogen peroxide at 1 mM, but not at 0.1 mM, for 15, 30 or 60 min followed by washout inhibited, in a time-dependent manner, the subsequent ability of acetylcholine (10 nM–3 μM) to induce endothelium-dependent relaxation. Furthermore, incubation with hydrogen peroxide 1 mM (30 min, followed by washout) also inhibited relaxation induced by glyceryl trinitrate (1–100 nM) or isoprenaline (10 nM–3 μM) in endothelium-denuded rings.
5. Incubation with 3-amino-1,2,4-triazole (50 mM, 90 min, followed by washout) had no effect by itself on relaxation induced by acetylcholine, glyceryl trinitrate or isoprenaline. In contrast, pretreatment with 3-amino-1,2,4-triazole led to profound enhancement of the ability of hydrogen peroxide (1 mM, present for final 30 min of the 90 min incubation) to block relaxation to acetylcholine, glyceryl trinitrate or isoprenaline.
6. On the basis of the actions of 3-amino-1,2,4-triazole, it is likely that endogenous catalase plays an important role in the protection of vascular reactivity of rat aorta against oxidant damage by high (1 mM) but not lower (0.1 mM) concentrations of hydrogen peroxide. The data are consistent with the promotion of non-selective damage to the vascular smooth muscle cells by hydrogen peroxide, but endothelial damage may also be sustained.

     

Percutaneous Penetration Kinetics of Nitroglycerin and Its Dinitrate Metabolites Across Hairless Mouse Skin in Vitro

The percutaneous penetration kinetics of the antianginal, nitroglycerin (GTN), and its primary metabolites, 1,2- and 1,3-glyceryl dinitrate (1,2- and 1,3-GDN), were evaluated in vitro, using full-thickness hairless mouse skin. GTN and the 1,2- and 1,3-GDNs were applied (a) in aqueous solution as pH 7.4 phosphate-buffered saline (PBS) and (b) incorporated into lipophilic ointment formulations. The cutaneous transformation of GTN to its dinitrate metabolites was detected, but no interconversion between 1,2-GDN and 1,3-GDN was observed. Following application of the nitrates in PBS solution, all three compounds exhibited steady-state transport kinetics. The steady-state flux of GTN (8.9 ± 1.5 nmol cm^–2 hr^–1) was significantly greater (P < 0.05) than those of 1,2-GDN (0.81 ± 0.54 nmol cm^–2 hr^–1) and 1,3-GDN (0.72 ± 0.20 nmol cm^–2 hr^–1). The corresponding permeability coefficient () for GTN (20 ± 3 × 10^–3 cm hr^–1) was significantly larger than the corresponding values for 1,2-GDN (1.4 ± 0.9 × 10^–3 cm hr^–1) and 1,3-GDN (1.2 ± 0.4 × 10^–3 cm hr^–1), which were statistically indistinguishable (P > 0.05). Further analysis of the transport data showed that the differences between GTN and the GDNs could be explained by the relative stratum corneum/water partition coefficient (K _s) values of the compounds. The apparent partition parameters, defined as = K _s · h [where h is the diffusion path length through stratum corneum (SC)] were 19.8 ± 2.5 × 10^–2 cm for GTN and 1.91 ± 1.07 × 10^–2 and 1.81 ± 0.91 × 10^–2 cm for 1,2- and 1,3-GDN, respectively. However, when the nitrates were administered in an ointment base, the apparent partition parameter (') and permeability coefficient (') of GTN markedly decreased, to 2.51 ± 0.75 × 10^–2 cm and 1.6 ± 0.3 × 10^–3 cm hr^–1, respectively. In contrast, the ' and ' results for 1,2- and 1,3-GDN were not significantly different (P > 0.05) from the corresponding and values, which were measured following dosing as aqueous solutions. As a result, the steady-state fluxes of all three nitrates from the ointment formulation were comparable (GTN, 154 ± 28 nmol cm^–2 hr^–1; 1,2-GDN, 162 ± 22 nmol cm^–2 hr^–1; 1,3-GDN, 162 ± 34 nmol cm^–2 hr^–1). It follows that the dinitrates can be as efficiently delivered across the skin as GTN when a suitable formulation is employed. This finding may support transdermal therapy using 1,2- or 1,3-GDN if, indeed, they are found to be pharmacologically effective.     

静脉注射硝酸甘油诱导大鼠脑膜核因子-κB表达增强

目的观察偏头痛大鼠模型不同时相脑膜核因子-κB(NF-κB)的表达特征.方法采用静脉注射硝酸甘油(GTN)法建立大鼠偏头痛模型,应用免疫组织化学法观察对照组、GTN iv 后0.5,1.0, 1.5, 2.0, 4.0 h组脑膜NF-κB阳性染色细胞的分布,采用Western印迹法观察相应时间点脑膜核NF-κB的蛋白表达量.结果 GTN iv后0.5 h即出现大鼠脑膜NF-κB核阳性反应和核NF-κB蛋白表达量增高,1.5 h核NF-κB蛋白表达量达高峰,然后逐渐回落,至4 h接近正常水平.结论 GTN iv后早期脑膜呈时限性核NF-κB蛋白表达增强,提示NF-κB蛋白表达增强可能与偏头痛有关.     

N-acetylcysteine infusion in viral myocarditis:: A case report

N-acetylcysteine improves survival in established acute liver failure following paracetamol overdose by reducing the incidence of multiorgan failure. These benefits are thought to be related to decreased tissue hypoxia by the enhancement of both oxygen delivery and oxygen extraction. Similar findings have been recorded in critically ill patients from an alternative aetiology. The cardiovascular properties of N-acetylcysteine are to increase stroke volume index, and thus cardiac output, although there is no effect on cardiac output in normal subjects. N-acetylcysteine is known to improve myocardial contraction in a hamster model of chronic myocardial ischaemia, but such effects have not previously been described in humans. We report the beneficial circulatory effect of N-acetylcysteine in a patient with marked left ventricular dysfunction secondary to acute viral myocarditis.     

硝酸甘油耐受对心肌缺血/再灌注损伤影响的研究

目的验证硝酸甘油(GTN)耐受对耐受产生后的心肌缺血/再灌注损伤的影响。方法雄性SD大鼠随机分组,分别接受GTN[600μg/(kg.h)]或生理盐水静脉滴注12h。检验耐受的产生,耐受和对照大鼠接受40min缺血和4h再灌注。检测心肌细胞凋亡(TUNEL法)、心肌坏死面积(Evansblue-TTC染色)和血清肌酸激酶(CK)、乳酸脱氢酶(LDH)活性。结果与单纯心肌缺血/再灌注相比,硝酸甘油耐受引起了再灌注后心肌凋亡比例、心肌坏死面积和血清心肌酶活性的显著增高,而单纯耐受没有对心脏造成明显损伤。结论实验结果提示除了使心血管对硝酸甘油的敏感性降低外,耐受对再灌注心脏存在一种潜在的损伤作用。     

The clinical efficacy of cosmeceutical application of liquid crystalline nanostructured dispersions of alpha lipoic acid as anti-wrinkle

Topical 5% alpha lipoic acid (ALA) has shown efficacy in treatment of photo-damaged skin. The aim of this work was to evaluate the potential of poloxamer (P407) gel as a vehicle for the novel lipid base particulate system (cubosome dispersions) of ALA. Cubosome dispersions were formulated by two different approaches, emulsification of glyceryl monoolein (GMO) and poloxamer (P407) in water followed by ultrasonication, and the dilution method using a hydrotrope. Three different concentrations of GMO were used to formulate the cubosome dispersions using the first method, 5% (D1), 10% (D2) and 15% w/w (D3). In the second technique an isotropic liquid was produced by combining GMO with ethanol, and this isotropic liquid was then diluted with a P407 solution (D4). The dispersions were characterized by zeta potential, light scattering techniques, optical and transmission electron microscopy, encapsulation efficiency and in vitro drug release. Results showed that D4 was not a uniform dispersion and that D1, D2 and D3 were uniform dispersions, in which by increasing the GMO content in the dispersion, the size of the cubosomes decreased, zeta potential became more negative, encapsulation efficiency increased up to 86.48% and the drug release rate was slower. P407 gels were prepared using the cold method. Two concentrations of P407 gel were fabricated, 20 and 30% w/w. P407 gels were loaded with either ALA or dispersions containing ALA cubosomes. P407 gels were characterized by critical gelation temperature, rheological measurements and in vitro drug release studies. Results suggested that by increasing P407 concentration, the gelation temperature decreases and viscosity increases. Drug release in both cases was found to follow the Higuchi square root model. Gel loaded with ALA cubosomes provided a significantly lower release rate than the gel loaded with the un-encapsulated ALA. A double blinded placebo controlled clinical study was conducted, aiming to evaluate the efficacy as an anti-wrinkle agent and volunteer’s satisfaction upon application of topical 30% P407 gel loaded with ALA cubosomes. Results indicated reduction in facial lines, almost complete resolution of fine lines in the periorbital region and upper lip area and overall improvement in skin color and texture in most volunteers. There were no instances of irritation, peeling or other apparent adverse side effects.     

Cigarette smoking and albuminuria are associated with impaired arterial smooth muscle function in patients with type 2 diabetes mellitus: a FIELD substudy

AimImpaired arterial function has been implicated in diabetes-related atherosclerosis, but its determinants in high-risk adults have not been well characterised. We investigated factors associated with impaired arterial function in adults with type 2 diabetes.MethodsFlow-mediated dilatation (a marker of endothelial function) and dilator response to glyceryl trinitrate (to assess smooth muscle function) of the brachial artery were assessed at baseline in 193 patients with type 2 diabetes from the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study. Traditional risk factors were assessed and a multivariable model was constructed to identify factors independently associated with impaired arterial function.ResultsMedian age was 64 years (interquartile range, 58–69; 61% male) and duration of diabetes was 4 years (interquartile range, 2–9). Flow-mediated dilatation (3.06 ± 0.25%, mean ± SEM) was severely impaired but not significantly associated with other risk factors. Dilator responses to glyceryl trinitrate (10.56 ± 0.52%) were significantly and independently impaired in past and present cigarette smokers (P = 0.005) and in subjects with increased urinary albumin/creatinine ratio (P = 0.01).ConclusionsIn adults with type 2 diabetes and known or suspected atherosclerosis, arterial smooth muscle-dependent dilatation was shown to be significantly impaired in cigarette smokers and those with elevated urinary albumin levels.     

硝酸甘油软膏治疗肛裂的多中心随机对照研究

目的评价硝酸甘油软膏治疗肛裂的临床疗效和安全性。方法采用多中心、随机、双盲、安慰剂平行对照的临床试验方法,从7个临床中心入组240例慢性肛裂患者,按随机数字表法随机分为试验组（硝酸甘油软膏,120例）和对照组（凡士林软膏,120例）,疗程为8周。比较两组肛裂愈合率、肛裂疼痛强度VAS评分、肛管静息压的变化及不良反应事件发生率。结果共有221例（92．1％）完成了试验,其中试验组114例,对照组107例。治疗终点（56d）,试验组和对照组肛裂愈合率分别为78．9％（90／114）和29．0％（31／107）,排粪后肛裂疼痛VAS评分下降率分别为（94．8±15．7）％和（61．2±35．7）％,差异均有统计学意义（均P〈0．01）。试验组和对照组分别有12例和6例患者接受了肛门直肠测压,首次用药前后肛管静息压下降值试验组为（20．2±18．5）mmHg,对照组为（7．1±14．7）mmHg,但两组差异并无统计学意义（P=0．152）。试验组不良反应事件发生率明显高于对照组[42．1％（48／114）比913％（10／107）,P〈0．05],但不良反应事件主要为轻度的头痛、头胀,可自行缓解。结论硝酸甘油软膏可有效缓解肛裂疼痛,促进肛裂愈合,且使用安全、耐受性好。     

Dietary fish oil augments nitric oxide production or release in patients with Type 2 (non-insulin-dependent) diabetes mellitus

Summary Decreased release of nitric oxide from damaged endothelium is responsible for the impaired endothelium-dependent vasodilator responses found in animal models of vascular disease. Dietary supplementation with fish oils has been shown to augment endothelium-dependent relaxations, principally by improving the release of nitric oxide from injured endothelium. Using forearm venous occlusion plethysmography we studied vascular responses to 60, 120, 180 and 240 nmol/min of acetylcholine (an endothelium-dependent vasodilator) and 3, 6 and 9 nmol/min of glyceryl trinitrate (an endothelium-independent vasodilator) infused into the brachial artery in 23 patients with Type 2 (non-insulin-dependent) diabetes mellitus. N^G monomethyl-l-arginine was employed to inhibit stimulated and basal release of nitric oxide from the endothelium. On completion of the baseline studies patients randomly received either fish oil or matching olive oil capsules in a double-blind crossover fashion for 6 weeks followed by a 6-week washout period and a final 6-week treatment phase. Studies, identical to the initial baseline studies, were performed at the end of the active treatment periods at 6 and 18 weeks. Fish oil supplementation significantly improved forearm blood flow responses to each dose of acetylcholine when compared to the vasodilator responses recorded at baseline and after olive oil administration (p<0.01). Neither fish oil nor olive oil supplementation produced any significant changes in forearm blood flow to the incremental infusions of glyceryl trinitrate when compared with responses recorded during the baseline studies. N^G monomethyl-l-arginine significantly reduced forearm blood flow from maximal stimulated values to acetylcholine when compared to the uninhibited decline in flow to acetylcholine infusions at comparable time points (p<0.01). Treatment with fish oils improved endothelium-dependent responses to acetylcholine without altering endothelium-independent responses to glyceryl trinitrate. By increasing stimulated nitric oxide release from the endothelium fish oils may afford protection against vasospasm and thrombosis in patients with diabetes mellitus.     

Evidence of partially preserved endothelial dilator function in diseased coronary arteries

OBJECTIVE—To examine the effects of substance P (endothelium dependent vasodilator) and glyceryl trinitrate (endothelium independent vasodilator) on epicardial coronary arteries in patients with normal coronary angiograms and patients with coronary artery disease.
DESIGN—Intracoronary infusions of normal saline, the receptor mediated nitric oxide stimulant substance P (5.6 and 27.8 pmol/min each for five minutes), and glyceryl trinitrate (250 µg bolus) were given in 24 patients with coronary artery disease and stable angina, and in nine patients with normal angiograms. The diameter of proximal and distal coronary segments was measured by computerised quantitative angiography
RESULTS—Proximal segments of patients with coronary artery disease dilated less than those of patients with normal angiograms in response to 27.8 pmol/min substance P (mean (SEM): 7.9 (1.3)% v 15 (2.3)% respectively, p < 0.01). The proximal segments of diseased arteries also dilated less than those of "normal" arteries in response to glyceryl trinitrate (10.2 (1.6)% v 18.4 (2.9)%, respectively, p < 0.01). The responses of distal segments to substance P and glyceryl trinitrate were similar in the two patient groups. There were correlations (all p < 0.001) between the coronary diameter after substance P and after glyceryl trinitrate in normal proximal segments (r = 0.94) and normal distal segments (r = 0.64), in diseased proximal segments (r = 0.95) and diseased distal segments (r = 0.89), and for coronary stenoses (r = 0.93).
CONCLUSIONS—Proximal segments of patients with coronary disease dilated less than the proximal segments of "normal" patients in response to substance P and glyceryl trinitrate. The response to substance P is substantial and closely correlated with the response to glyceryl trinitrate in both "normal" patients and those with coronary disease. This suggests that although the proximal segments of diseased coronary arteries have a reduced capacity to dilate in response to direct stimulation of smooth muscle cell relaxation, they retain much of their endothelium dependent vasodilator function.


Keywords: endothelium; nitric oxide; coronary artery disease; glyceryl trinitrate