Acute effects of glucocorticoids on endothelial fibrinolytic and vasodilator function in humans

Acute coronary events occur most commonly in the morning, when circadian variations dictate that endogenous fibrinolytic activity is low and cortisol levels are high. We hypothesized that glucocorticoids would impair the acute fibrinolytic capacity of the endothelium because chronic glucocorticoid excess is associated with a prothrombotic state and endothelial vasomotor dysfunction. Twelve healthy subjects attended on 3 occasions and received oral metyrapone followed by intravenous saline or low-dose or high-dose hydrocortisone. Forearm blood flow and fibrinolytic indices were measured using venous occlusion plethysmography during intrabrachial bradykinin, acetylcholine, and sodium nitroprusside infusion.Hydrocortisone infusion had no effect on systemic concentrations of plasminogen activator inhibitor type 1 (PAI-1) or tissue plasminogen activator (t-PA; P = 0.10 and 0.95, respectively). Bradykinin caused a dose-dependent increase in plasma t-PA concentrations (P < 0.0001) that was unaffected by systemic hydrocortisone administration. Intrabrachial infusions of bradykinin, acetylcholine, and sodium nitroprusside all caused dose-dependent increases in forearm blood flow (P < 0.05) that were unaltered by hydrocortisone infusions.Short-term variations in plasma cortisol concentrations within the physiological range do not affect endothelial fibrinolytic or vasomotor function in healthy volunteers. These findings suggest that glucocorticoids do not exert acute effects on endothelial function in vivo in humans.     

Glucuronidation of resveratrol, a natural product present in grape and wine, in the human liver

1. Resveratrol, a polyphenolic compound present in grape and wine, has beneficial effects against cancer and protective effects on the cardiovascular system. It has been shown that the compound is sulphated in human liver and the aims of the present investigation were to study resveratrol glucuronidation in human liver microsomes and to determine whether flavonoids inhibit resveratrol glucuronidation. 2. A simple and reproducible radiometric assay for resveratrol glucuronidation was developed. The assay employed uridine-5'-diphosphoglucuronic acid-[14C] and unlabelled resveratrol. Resveratrol-glucuronide was isolated by TLC. The intra- and interassays variabilities were 1 and 1.5%, respectively. 3. The rate of resveratrol glucuronidation was measured in 10 liver samples. The mean +/- SD and median of resveratrol glucuronidation rate were 0.69 +/- 0.34 and 0.80 nmol/min/mg, respectively. Resveratrol glucuronosyl transferase followed Michaelis-Menten kinetics and the Km and Vmax (mean +/- SD; n = 5) were 0.15 +/- 0.09 mM and 1.3 +/- 0.3 nmol/min/mg, respectively. The intrinsic clearance was 11 +/- 4 x 10(-3) ml/min.mg. 4. The flavonoid quercetin inhibited resveratrol glucuronidation and its IC50 (mean +/- SD; n = 3) was 10 +/- 1 microM. Myricetin, catechin, kaempferol, fisetin and apigenin (all at 20 microM) inhibited resveratrol glucuronidation and the percent of control ranged between 46% (catechin) to 72% (apigenin). 5. The present results show that resveratrol is glucuronated in the human liver. Glucuronidation may reduce the bioavailability of this compound however, flavonoids inhibit resveratrol glucuronidation and such an inhibition might improve the bioavailability of resveratrol.     

Glucuronidation of resveratrol,a natural product present in grape and wine,in the human liver

1. Resveratrol, a polyphenolic compound present in grape and wine, has beneficial effects against cancer and protective effects on the cardiovascular system. It has been shown that the compound is sulphated in human liver and the aims of the present investigation were to study resveratrol glucuronidation in human liver microsomes and to determine whether flavonoids inhibit resveratrol glucuronidation. 2. A simple and reproducible radiometric assay for resveratrol glucuronidation was developed. The assay employed uridine-5′-diphosphoglucuronic acid-[¹⁴C] and unlabelled resveratrol. Resveratrol-glucuronide was isolated by TLC. The intra- and interassays variabilities were 1 and 1.5%, respectively. 3. The rate of resveratrol glucuronidation was measured in 10 liver samples. The mean ± SD and median of resveratrol glucuronidation rate were 0.69 ± 0.34 and 0.80 nmol/min/mg, respectively. Resveratrol glucuronosyl transferase followed Michaelis-Menten kinetics and the K_m and V_max (mean ± SD; n = 5) were 0.15 ± 0.09?mm and 1.3 ± 0.3 nmol/min/mg, respectively. The intrinsic clearance was 11 ± 4 × 10^?3 ml/min.mg. 4. The flavonoid quercetin inhibited resveratrol glucuronidation and its IC₅₀ (mean ± SD; n = 3) was 10 ± 1 μM. Myricetin, catechin, kaempferol, fisetin and apigenin (all at 20 μM) inhibited resveratrol glucuronidation and the percent of control ranged between 46% (catechin) to 72% (apigenin). 5. The present results show that resveratrol is glucuronated in the human liver. Glucuronidation may reduce the bioavailability of this compound however, flavonoids inhibit resveratrol glucuronidation and such an inhibition might improve the bioavailability of resveratrol.     

Barbital N-glucoside is not detected as a urinary excretion product of barbital in humans

A study was undertaken to determine if humans excreted barbital N-glucoside as a urinary metabolite following oral administration of barbital. A liquid chromatography method using gradient elution was developed for detecting and quantifying barbital N-glucoside and barbital in urine. Following a single oral dose of barbital to male caucasian and oriental subjects that had previously been shown to excrete amobarbital and phenobarbital N-glucosides, no barbital N-glucoside conjugate was observed in the urine. This result indicates that N-glucosylation of barbiturates is not a general pathway for the biodisposition of barbiturates in man.     

Cocaine effects in sleep-deprived humans

Eight normal healthy volunteers were tested in a reaction-time task and a work-output task after 24 and 48 h of sleep deprivation with and without 96 mg of inhaled cocaine. Cardiovascular changes and verbal report of mood change and drug effect were also monitored. Sleep deprivation produced a decrement in reaction-time performance which was reversed by inhalation of cocaine. Heart rate increased after cocaine both under non sleep-deprived conditions and sleep-deprived conditions. The magnitude of the drug-induced heart rate was, however, lower when subjects were deprived of sleep for 48 h. Verbal reports of cocaine effects were similar to those reported for amphetamine, with no evidence supporting the idea of a postdrug depression immediately after the acute effects of the drug dissipated, although some rebound effects were noted 8 h after drug administration.     

Opiate-induced pupillary effects in humans

The pupillary effects of several opiates were assessed in human volunteers (N = 6) by means of a newly developed hand-held pupilometer, Pupilscan. Static (diameter) and dynamic (light reflex) responses after morphine, heroin, codeine, oxycodone, oxymorphone and hydrocodone were recorded. The opiates caused dose-related decreases in pupillary size and in the velocity of constriction to a light stimulus. The velocity of redilation after a light stimulus was also decreased. These data indicate that opiates cause systematic changes in dynamic pupillary responses in humans and that measures of these changes may be useful in the quantitative estimation of drug-induced impairment.     

New methods to evaluate endothelial function: Non-invasive method of evaluating endothelial function in humans

Evidence has accumulated that impairment of vascular endothelial function is the initial step in the development of atherosclerosis. One important finding is impairment of the release of endothelium-dependent relaxing factor, which is now thought to be nitric oxide or its related substances, from endothelial cells. Flow-mediated dilatation has been known to be endothelium-dependent, and this can be detected during reactive hyperemia by high-resolution ultrasound in superficial arteries. Several coronary risk factors have been reported to be significantly related with decreased flow-mediated dilatation. We studied the association between the accumulation of coronary risk factors (hyperlipidemia, diabetes mellitus, hypertension, and current smoking habitus) and vascular endothelial function. The lower incidence of atherosclerosis in women before the menopause than that in men is an established epidemiological observation. Short-term estrogen therapy improves endothelial function in postmenopausal women. However, there are few reports on its long-term effects on endothelial function. Furthermore, we determined whether a reduced dosage of estrogen may maintain its beneficial effects. A similar improvement was also observed while women were on hormone replacement therapy even at the reduced dosage. Our results indicate that even at half the dose of estrogen, hormone replacement therapy may improve endothelial function in postmenopausal women.     

Antihypertensive,vasodilator and antioxidant effects of a vinifera grape skin extract

Cumulative evidence suggests that moderate wine consumption exerts a cardioprotective effect. We investigated the occurrence of an antihypertensive effect of an alcohol-free hydroalcoholic grape skin extract (GSE) obtained from skins of a vinifera grape (Vitis labrusca) in experimental rodent hypertension models. The vasodilator effect of GSE (polyphenols concentration 55.5 mg g(-1)) was also assessed in the isolated mesenteric vascular bed of Wistar rats and the antioxidant effect was studied on lipid peroxidation of hepatic microsomes. Oral administration of GSE significantly reduced systolic, mean and diastolic arterial pressure in Wistar rats with desoxycorticosterone acetate-salt and N(G)-nitro-L-arginine methyl ester (L-NAME) induced experimental hypertension. In the rat isolated mesenteric vascular bed pre-contracted with norepinephrine, bolus injections of GSE induced endothelium-dependent vasodilatation that was substantially inhibited by L-NAME, but not by indometacin, tetraethylammonium or glibenclamide. Lipid peroxidation of hepatic microsomes estimated as malondialdehyde production was concentration-dependently inhibited by GSE. In conclusion, the antihypertensive effect of GSE might be owing to a combination of vasodilator and antioxidant actions of GSE. These findings also suggest that the beneficial effect of moderate red wine consumption could be owing to an antihypertensive action induced by compounds occurring in the skin of vinifera grapes.     

内皮抑素基因表达产物对血管内皮细胞生长的抑制作用

目的探讨逆转录病毒介导内皮抑素基因转移的方法及其表达产物人内皮抑素对人血管内皮细胞的作用。方法以逆转录病毒为载体,转导内皮抑素基因至肺腺癌A549细胞,获得含内皮抑素基因的A549/Endo细胞。PCR方法检验外源性内皮抑素基因在宿主细胞中的整合。培养A549/Endo细胞,收集上清液。ELISA法检测上清液中内皮抑素的浓度,四唑盐比色试验(MTT)、流式细胞术(FCM)、原位细胞凋亡(TUNEL)观察该上清液对血管内皮细胞EA hy926 的抑制作用。结果PCR法证实A549/Endo细胞基因组中整合有外源性内皮抑素基因。A549/Endo细胞(1×105/ml)培养48h后,上清液中内皮抑素含量为(348±120) pg/ml,MTT法显示含内皮抑素的上清液能明显抑制EA hy926细胞的生长。FCM、TUNEL法显示内皮抑素可诱导EA hy926 凋亡。结论逆转录病毒能高效介导内皮抑素基因转移,内皮抑素基因表达产物能明显抑制人血管内皮细胞的生长,诱导其凋亡。     

Clinical effects produced by a standardized herbal medicinal product of Hibiscus sabdariffa on patients with hypertension. A randomized, double-blind, lisinopril-controlled clinical trial

Hibiscus sabdariffa L. (Malvaceae) has been used in different countries as an antihypertensive. Pharmacological work has demonstrated that this effect is probably produced by a diuretic activity and inhibition of the angiotensin-converting enzyme (ACE). Two clinical trials have confirmed the antihypertensive effect using watery infusions, in which a natriuretic effect was also detected. To compare therapeutic effectiveness, tolerability, and safety, as well as the effect on serum electrolytes and the ACE inhibitory effect of a herbal medicinal product prepared from the dried extract of H. sabdariffa calyxes (HsHMP) with those of lisinopril on patients with hypertension (HT), a randomized, controlled, and double-blind clinical trial was conducted. Patients of either sex, 25 - 61 years of age, with hypertension stage I or II, were daily treated for 4 weeks with the HsHMP, 250 mg of total anthocyanins per dose (experimental group), or 10 mg of lisinopril (control group). Outcome variables included effectiveness (diastolic blood pressure [DBP] reduction, >or= 10 mmHg), safety (absence of pathological modifications in the biochemical tests of hepatic and renal function), tolerability (absence of intense side effects), effect on serum electrolytes, and effect on ACE activity. Basal analysis included 193 subjects (100 in the experimental group), while outcome variable analysis integrated 171. Results showed that the experimental treatment decreased blood pressure (BP) from 146.48/97.77 to 129.89/85.96 mmHg, reaching an absolute reduction of 17.14/11.97 mmHg (11.58/12.21%, p < 0.05). The experimental treatment showed therapeutic effectiveness of 65.12 % as well as tolerability and safety of 100 %. BP reductions and therapeutic effectiveness were lower than those obtained with lisinopril (p < 0.05). Under the experimental treatment, the serum chlorine level increased from 91.71 to 95.13 mmol/L (p = 0.0001), the sodium level showed a tendency to decrease (from 139.09 to 137.35, p = 0.07), while potassium level was not modified. ACE plasmatic activity was inhibited by HsHMP from 44.049 to 30.1 Units (Us; p = 0.0001). In conclusion, the HsHMP exerted important antihypertensive effectiveness with a wide margin of tolerability and safety, while it also significantly reduced plasma ACE activity and demonstrated a tendency to reduce serum sodium (Na) concentrations without modifying potassium (K) levels. Further studies are necessary for evaluating the dose-dependency of HsHMP and for detecting lower effective doses.     

The effects of dextroamphetamine and phenobarbital on a simplified standardized CFF measure

Summary The effects of a CNS-stimulant, CNS-depressant, and placebo on CFF thresholds of 24 subjects were determined using a flicker-fusion test based on the psychophysical method of limits. Four conditions, 10 mg of d-amphetamine, 65 mg of phenobarbital, inert placebo, and no-drug, were applied in a repeated measures design under double-blind conditions. Each session lasted three hours. Pulse was taken concurrent with CFF, and an adjective checklist of subjective feeling was administered at the end of each session.Both CFF and mood checklist were sensitive to phenobarbital. Pulse differences appeared only under d-amphetamine. Longer test sessions, more frequent testing or more subjects seemed advisable for future work. The method of CFF measurement used, most amenable to the aforementioned extensions, appeared at least as sensitive as the more complex techniques previously employed.This investigation was supported by the Warner-Lambert Research Institute, Morris Plains, New Jersey. We would like to thank Dr. Jerry Weisberg, of Warner-Lambert, for his advice regarding the medical aspects of the study, and Dr. John Walsh, of Fordham University, for his extensive assistance in the analysis of the data.     

Discriminative-stimulus effects of modafinil in cocaine-trained humans

Modafinil is a novel stimulant that is effective in the treatment of narcolepsy and excessive daytime sleepiness. In vitro and in vivo neuropharmacological data suggest that the mechanism of action of modafinil is distinct from that of prototypical abused stimulants like cocaine and d-amphetamine. In the present experiment, six human volunteers with recent histories of cocaine use learned to discriminate 150 mg oral cocaine HCL. After acquiring the discrimination (i.e. > or = 80% correct responding on 4 consecutive days), a range of doses of oral cocaine (50, 100, and 150 mg), modafinil (200, 400, and 600 mg), and placebo were tested to determine if they shared discriminative-stimulus and self-reported effects with 150 mg cocaine. Methylphenidate (60 mg) and triazolam (0.5 mg) were included as positive and negative controls, respectively. Cocaine and methylphenidate, but neither modafinil nor triazolam, produced cocaine-like discriminative-stimulus, subject-rated, and cardiovascular effects. The results of the present experiment suggest that cocaine discrimination in humans is pharmacologically specific within and across drug classes.     

Discriminative stimulus effects of alcohol in humans

The discriminative stimulus effects of alcohol were examined in 11 healthy moderate alcohol users. Study days occurred 5 days per week for 12–25 total days. Each day, participants completed visual-analog reports of drug effect and drug-discrimination tasks at 30-min intervals for 2.5 h following oral alcohol administration. Participants completed three phases. During the training phase, which occurred on the first 4 study days, participants were trained to discriminate color-coded placebo and alcohol doses (0 vs. 0.45 g per liter of body water (g/lbw)). Participants then completed a control phase, during which accurate drug-discrimination performance was verified. Finally, participants completed a testing phase, during which both training and intermediate doses (0.15 and 0.30 g/lbw) were administered. During the testing phase, 25 and 100% of responses occurred on the alcohol key at the 0- and 0.45-g/lbw doses, respectively, indicating that discrimination responding remained intact. At the low dose (0.15 g/lbw), 25% of the subjects responded on the alcohol key, whereas 75% of the subjects responded on the alcohol key at the moderate dose (0.30 g/lbw), indicating dose-related generalization to the training doses. These results confirm cross-species generality in the discriminative stimulus effects of alcohol, and further establishes the utility of human laboratory drug-discrimination procedures for analysis of the functional effects of alcohol.     

Serotonergic mechanisms of cocaine effects in humans

The objective of this study was to investigate the role of serotonin (5-HT) in mediating the effects of cocaine in humans. To accomplish this, 12 subjects each participated in two randomized, double-blind test sessions separated by 1 week. In one session, subjects underwent acute depletion of the 5-HT amino acid precursor tryptophan (TRP), followed by a test dose of intranasal cocaine. In the other session, the cocaine test dose was preceded by sham depletion. Subject ratings of cocaine high were significantly lower following active TRP depletion than after the sham procedure. Subjects also showed an earlier but less sustained rise in self-rated nervousness during active TRP depletion. These findings are consistent with the hypothesis that 5-HT may be involved in mediating the euphorigenic and modulating the anxiogenic effects of cocaine in humans, either directly or through actions on other (e.g., dopaminergic) systems.     

Stereoselective effects of disopyramide enantiomers in humans

The effects of 100 mg of (S+)- and R(-)-disopyramide infused over 20 min on systolic time intervals and the QT interval were compared in five healthy volunteers. S(+)-disopyramide maximally prolonged the QTI (QT corrected for heart rate) by 10% (p less than 0.05); R(-)-disopyramide had no effect on QTI. R(-)-disopyramide maximally prolonged the preejection period and shortened the left ventricular ejection time corrected for heart rate (PEPI and LVETI), and increased the ratio of PEP/LVET by 32, 6, and 52%, respectively; S(+)-disopyramide maximally increased PEPI and PEP/LVET 15 and 20%, respectively (p less than 0.05), and had no effect on LVETI. These data suggest that the electrophysiologic effects of disopyramide enantiomers are different, and that S(+)-disopyramide has a less negative inotropic effect than R(-)-disopyramide. Changes in response were fitted to a pharmacokinetic-pharmacodynamic model, which estimated that 72% of the negative inotropic effects associated with racemic disopyramide may be avoided by using S(+)-disopyramide.     

Subjective effects of khat chewing in humans

The subjective effects of Khat (Catha edulis) chewing were studied in 14 male somali, habitual khat users, by means of the Addiction Research Center Inventory (ARCI) questionnaire and of visual analogue scales concerning mood and appetite. Results show that euphoria, improved intellectual efficiency and alertness were associated with khat consumption in 10 subjects. In contrast, the remaining 4 subjects experienced only dysphoria and mild sedation. These latter effects were present in all the subjects in the post-chewing period. In spite of these subjective differences, blood pressure and pulse rate increased in all the volunteers studied. As a whole, these results are consistent with the presumed amphetamine-like action of khat, but suggest also a major role of environmental factors in the expression of these actions.     

Time-dependent pharmacodynamic effects of phenobarbital in humans

The relationship between the serum concentration of phenobarbital and its pharmacodynamic effects was assessed in a double-blind controlled study in eight normal volunteers who were given single oral doses of phenobarbital (200 mg) and placebo according to a randomized cross-over design. Compared with the placebo session, phenobarbital was found to induced CNS-depressing effects as assessed by visual analogue rating scales (VARS) and critical flicker fusion tests (CFF), whereas no significant effects were detected on choice reaction times, tappings, and digit symbol substitutions. There was a clear-cut dissociation between the time course of serum phenobarbital levels, which remained at a plateau throughout most of the period of observation (up to 72 h) and its subjective (VARS) and objective (CFF) effects, which could be documented only for up to 9 h after administration. These data suggest that pharmacodynamic tolerance develops rapidly even after a single oral dose of the drug. Multiple Sleep Latency Tests (MSLTs) were also performed in the same subjects and showed that phenobarbital increases diurnal drowsiness and attenuates the circadian variation in drowsy state that is seen under control conditions. MLSTs appeared to be superior to other tests in documenting the sedative effects of the barbiturate.     

Therapeutic strategies targeting endothelial function in humans: clinical implications

Persistent oxidative stress in the vascular wall may lead to endothelial dysfunction, a pathological process widely implicated in the morbidities observed in a spectrum of cardiovascular disease. The production of reactive oxygen species (ROS) is regulated by various oxidase enzymes and mitochondrial electron transport mechanisms. Nitric oxide (NO) is a key mediator of endothelial function via its effect on endothelium dependent vascular relaxation. Therapeutic interventions aimed to increase NO bioavailability in the vasculature may improve the long term cardiovascular outcome for healthy individuals, high-risk subjects, and patients with advanced atherosclerosis. Current therapeutic strategies focus on enhancing synthesis or lowering oxidative inactivation of NO in human vasculature. Of the available therapeutic agents, angiotensin converting enzyme inhibitors and statins have shown most promise at improving endothelial function and cardiovascular outcome after long term administration. Other therapeutic approaches may also be useful towards improving endothelial dysfunction. These strategies include targeting NO synthesis by modulation of endothelial nitric oxide synthase (eNOS) coupling, such as folates and tetrahydrobiopterin. Evidence for the benefits of gene therapy to improve endothelial function is also emerging. However, the long term direct clinical benefit of these strategies aimed to improve endothelial function still remains unclear.