A stepwise integrated multi-system to screen quality markers of Chinese classic prescription Qingzao Jiufei decoction on the treatment of acute lung injury by combining 'network pharmacology-metabolomics-PK/PD modeling'

BACKGROUND

Previously, we have investigated the therapeutic mechanism of Qingzao Jiufei Decoction (QZJFD), a Chinese classic prescription, on acute lung injury (ALI), however, which remained to be further clarified together with the underlying efficacy related compounds for quality markers (Q-markers).

HYPOTHESIS/PURPOSE

To explore Q-markers of QZJFD on ALI by integrating a stepwise multi-system with 'network pharmacology-metabolomics- pharmacokinetic (PK)/ pharmacodynamic (PD) modeling'.

METHODS

First, based on in vitro and in vivo component analysis, a network pharmacology strategy was developed to identify active components and potential action mechanism of QZJFD on ALI. Next, studies of poly-pharmacology and non-targeted metabolomics were used to elaborate efficacy and verify network pharmacology results. Then, a comparative PK study on active components in network pharmacology was developed to profile their dynamic laws in vivo under ALI, suggesting Q-marker candidates. Next, quantified analytes with marked PK variations after modeling were fitted with characteristic endogenous metabolites along drug concentration-efficacy-time curve in a PK-PD modeling to verify and select primary effective compounds. Finally, Q-markers were further chosen based on representativeness among analytes through validity analysis of PK quantitation of primary effective compounds.

RESULTS

In virtue of 121 and 33 compounds identified in vitro and in vivo, respectively, 33 absorbed prototype compounds were selected to construct a ternary network of '20 components-47 targets-113 pathways' related to anti-ALI of QZJFD. Predicted mechanism (leukocytes infiltration, cytokines, endogenous metabolism) were successively verified by poly-pharmacology and metabolomics. Next, 18 measurable components were retained from 20 analytes by PK comparison under ALI. Then, 15 primary effective compounds from 18 PK markers were further selected by PK-PD analysis. Finally, 9 representative Q-markers from 15 primary effective compounds attributed to principal (chlorogenic acid), ministerial (methylophiopogonanone A, methylophiopogonanone B), adjuvant (sesamin, ursolic acid, amygdalin), conductant drugs (liquiritin apioside, liquiritigenin and isoliquiritin) in QZJFD, were recognized by substitutability and relevance of plasmatic concentration at various time points.

CONCLUSION

9 Q-markers for QZJFD on ALI were identified by a stepwise integration strategy, moreover, which was a powerful tool for screening Q-makers involved with the therapeutic action of traditional Chinese medicine (TCM) prescription and promoting the process of TCM modernization and scientification.

Trabectedin (YondelisTM, formerly ET-743), a mass balance study in patients with advanced cancer

Trabectedin (Yondelis, formerly ET-743) is an anti-cancer drug currently undergoing phase II development. Despite extensive pharmacokinetic studies, the human disposition and excretory pathways of trabectedin remain largely unknown. Our objective was to determine the mass balance of trabectedin in humans. To this aim, we intravenously administered [(14)C]trabectedin to 8 cancer patients, followed by collection of whole blood, urine and faeces samples. A 24-h infusion was administered to 2 patients, whereas the other 6 patients received a 3-h infusion. Levels of total radioactivity and unchanged trabectedin were determined and used for calculation of pharmacokinetic parameters. No schedule dependency of pharmacokinetic parameters was observed apart from C(max). Plasma and whole blood concentrations of [(14)C]trabectedin related radioactivity were comparable. Only 8% of the plasma exposure to [(14)C]trabectedin related compounds is accounted for by trabectedin, indicating the importance of metabolism in trabectedin elimination. Trabectedin displays a large volume of distribution (+/-1700 L), relative to total radioactivity (+/-220 L). [(14)C]trabectedin related radioactivity is mainly excreted in the faeces (mean: 55.5% of the dose). Urinary excretion accounts for 5.9% of the dose on average resulting in a mean overall recovery of 61.4% (3-h administration schedule). The excretion of unchanged trabectedin is very low both in faeces and in urine (< 1% of dose). In conclusion, trabectedin is extensively metabolised and principally excreted in the faeces.

Simple and sensitive liquid chromatographic quantitative analysis of the novel marine anticancer drug Yondelis (ET-743, trabectedin) in human plasma using column switching and tandem mass spectrometric detection

The development of a simple and sensitive assay for the quantitative analysis of the marine anticancer agent Yondelis (ET-743, trabectedin) in human plasma using liquid chromatography (LC) with column switching and tandem mass spectrometric (MS/MS) detection is described. After protein precipitation with methanol, diluted extracts were injected on to a small LC column (10 x 3.0 mm i.d.) for on-line concentration and further clean-up of the sample. Next, the analyte and deuterated internal standard were back-flushed on to an analytical column for separation and subsequent detection in an API 2000 triple-quadrupole mass spectrometer. The lower limit of quantitation was 0.05 ng mL(-1) using 100 micro l of plasma with a linear dynamic range up to 2.5 ng ml(-1). Validation of the method was performed according to the most recent FDA guidelines for bioanalytical method validation. The time needed for off-line sample preparation has been reduced 10-fold compared with an existing LC/MS/MS method for ET-743 in human plasma, employing a labor-intensive solid-phase extraction procedure for sample pretreatment. The proposed column switching method was successfully applied in phase II clinical trials with Yondelis and pharmacokinetic monitoring.

Complete protection by high-dose dexamethasone against the hepatotoxicity of the novel antitumor drug yondelis (ET-743) in the rat

Yondelis (ET-743) is a promising antitumor drug with hepatotoxic properties in animals and humans. Here the hypothesis was tested that dexamethasone can ameliorate manifestations of yondelis-induced hepatotoxicity in the female Wistar rat, which is the animal species with the highest sensitivity toward the adverse hepatic effect of yondelis. Hepatotoxicity was adjudged by measurement of plasma levels of alkaline phosphatase, aspartate aminotransferase, and bilirubin, and by liver histopathology. Yondelis (40 micro g/kg i.v.) alone caused a dramatic elevation of plasma alkaline phosphatase, aspartate aminotransferase, and bilirubin levels, and degeneration and patchy focal necrosis of bile duct epithelial cells. Pretreatment of rats with dexamethasone (5-20 mg/kg, p.o.) 24 h before yondelis ameliorated or abrogated the biochemical and histopathological manifestations of yondelis-induced liver changes. In contrast, when dexamethasone was administered simultaneously with yondelis, its toxicity was not reduced. Pretreatment with dexamethasone (10 mg/kg) also reversed the gene expression changes induced by yondelis in rat liver. However, dexamethasone pretreatment did not interfere with the antitumor efficacy of yondelis in rats bearing the 13762 mammary carcinoma or in four murine models. Dexamethasone (10 mg/kg) administered 24 h before yondelis decreased hepatic levels of yondelis dramatically compared with those obtained after administration of yondelis alone, whereas yondelis plasma levels after the drug combination were not markedly different from those in rats on yondelis alone. The results suggest that pretreatment with high-dose dexamethasone effectively protects rats against yondelis-mediated hepatic damage by decreasing hepatic exposure to yondelis, perhaps linked to induction of metabolism by cytochrome P450 enzymes. Pretreatment with high-dose dexamethasone should be investigated in patients who receive yondelis to ameliorate its unwanted effect on the liver.

Search for metabolites of ecteinascidin 743, a novel, marine-derived, anti-cancer agent, in man

Ecteinascidin 743 (ET-743) is a potent anti-tumoral agent of a marine origin. It is currently being tested in phase II clinical trials using a 3-weekly 24-h i.v. infusion of 1500 microg/m(2) and 3-h infusions of 1650 microg/m(2). Knowledge of the metabolism of ET-743 is, however, still scarce. In the present study, a qualitative chromatographic discovery of metabolites of ET-743 in man is reported. ET-743 and its demethylated analog ET-729 were incubated at 37 degrees C in the presence of enzyme systems, pooled human microsomes, pooled human plasma and uridine 5'-diphosphoglucuronyltransferase, respectively, in appropriate media. Reaction products were investigated chromatographically using photodiode array and ion spray-mass spectrometric detection (LC-MS). The main reaction products in microsomal incubations of ET-743 resulted from a remarkable breakdown of the molecule. In plasma the drugs were deacetylated, and the transferase did actually yield a glucuronide of both ET-743 and ET-729. In contrast, screening of urine, plasma and bile, collected from patients treated with ET-743 at the highest dose levels, using a sensitive LC-MS assay, did not result in detection of ET-729 and metabolites which were generated in vitro. The urinary excretion of ET-743 in man was lower than 0.7% of the administered dose for a 24-h infusion.

Chronic endothelin blockade in dogs with pacing-induced heart failure: possible modulation of sympathoexcitation

BACKGROUND

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide elaborated by many cell types. Plasma ET-1 levels are significantly augmented in patients and experimental animals with heart failure. Enhanced levels of ET-1 may contribute to myocardial depression and alterations in sympathetic nerve activity in the setting of chronic heart failure. The effects of chronic blockade of endothelin A (ET(A)) receptors on the development and severity of experimental heart failure and sympathoexcitation were evaluated in these experiments using the specific ET(A) antagonist, PD156707.

METHODS AND RESULTS

Four groups of conscious, chronically instrumented mongrel dogs were administered either PD156707 (750 mg orally thrice daily) or a placebo starting 1 day before ventricular pacing or a sham (nonpaced) period. Before pacing or the sham period, baseline hemodynamic and plasma norepinephrine (NE) measurements were made. Hemodynamic and NE measurements were made every 3 to 4 days for the next 28 days. All parameters were relatively stable in nonpaced dogs administered placebo. Paced placebo dogs showed classic hemodynamic and sympathoexcitatory changes indicative of heart failure. Nonpaced dogs administered PD156707 showed a significant decrease in mean arterial pressure and total peripheral resistance beginning 3 days after drug administration. Myocardial function was not affected by PD156707 in nonpaced dogs. In paced dogs, PD156707 also reduced arterial pressure and peripheral resistance. Changes in myocardial function were small and insignificant. Paced dogs administered PD156707 showed an approximately 50% lower increase in plasma NE level from days 10 to 24 compared with paced dogs administered placebo (941.8 +/- 122.8 vs 501.1 +/- 92.6 pg/mL at 17 days; P < .01).

CONCLUSIONS

These data suggest that ET-1 contributes to the maintenance of arterial pressure in both sham dogs and dogs paced into heart failure. ET-1 does not appear to have a potent effect on inotropic state, but the data strongly suggest that ET-1 may contribute to the progressive deterioration of circulatory function in heart failure by mediating sympathoexcitation and enhancing plasma NE concentration.

Rapid microbore liquid chromatographic analysis of biphenyldimethyl dicarboxylate in human plasma with on-line column switching

A fully automated method including microbore liquid chromatography and column switching was developed for the analysis of biphenyldimethyl dicarboxylate (DDB) from human plasma samples. After direct injection of plasma samples (100 microl) into the system, deproteinization and analyte fractionation occurred on a Capcell Pak MF Ph-1 column (20x4 mm I.D.) and the DDB fraction was transferred from the MF Ph-1 column to an intermediate column (35x2 mm I.D.) using 15% acetonitrile in phosphate buffer (50 mM, pH 7.0). The main separation was performed on a microbore C18 column (150x1.5 mm I.D.) using 45% acetonitrile in water. The method showed excellent sensitivity (detection limit of 5 ng/ml) and good precision (CV.< or =3.0%), and shortened total analysis time (20 min). In the concentration range of 5-200 ng/ml, the mean recovery was 90.7+/-1.8% and the response was linear (r2> or =0.999).

Dietary defatted sesame flour decreases susceptibility to oxidative stress in hypercholesterolemic rabbits

Plant glucosides possess antioxidative properties due to their ability to scavenge free radicals. Sesame seeds contain a class of these compounds, the sesaminol glucosides. To evaluate their antioxidative activity in vivo, we fed rabbits diets containing 1% cholesterol (Chol) with or without 10% defatted sesame flour (DSF) (containing 1% sesaminol glucosides) for 90 d. We determined the susceptibility of their tissues to oxidation ex vivo as well as serum total cholesterol (TC), phospholipid (PL), triglyceride (TG) and HDL cholesterol (HDL-C) concentrations. Serum TC, HDL-C, PL and TG levels were unaffected by the addition of DSF. The HDL-C in the Chol + DSF group was greater than in the Chol group at 45 d. Both were greater than in the groups that did not consume cholesterol. Liver TC and TG were significantly lower in rabbits fed the diet containing DSF plus 1% cholesterol than in those fed 1% cholesterol alone. Lipid peroxidation activity, measured as 2-thiobarbituric acid reactive substances (TBARS), was lower in the liver (P < 0.05) and serum (P = 0.06) of rabbits fed DSF plus cholesterol than in rabbits fed the cholesterol diet. Although we did not detect sesaminol glucosides in peripheral tissues, we observed abundant quantities of sesaminol in rabbits fed DSF, the principal metabolite. Our findings suggest that feeding DSF to rabbits does not protect cholesterol-induced hypercholesterolemia, but may decrease susceptibility to oxidative stress in rabbits fed cholesterol, perhaps due to the antioxidative activity of sesaminol.

Coronary arteriopathy in monkeys following administration of CI-1020, an endothelin A receptor antagonist

A selective non-peptide endothelin A (ETA) receptor antagonist, CI-1020, was administered to cynomolgus monkeys intravenously (i.v.) for 2 or 4 wk and orally for 4 wk. Groups consisting of 3 animals of each sex received CI-1020 at 1, 5, and 10 mg/kg/hr (i.v.) or orally at 250, 500, and 750 mg/kg body weight for 4 wk. Control animals received the vehicle only. In a separate experiment, 1 male was infused with 10 mg/kg/hr for 2 wk, and Monastral blue dye was administered i.v. to facilitate localization of lesions to the vascular walls. One female was administered saline and the dye and served as a control. One female at 1 mg/kg/hr was found dead at week 2, and 1 female at 5 mg/kg/hr was euthanatized during week 4 as a result of severe thigh swelling at the catheter site. Macroscopically, extramural coronary arteries appeared thickened and nodular in the 4-wk i.v. study in the female found dead at 1 mg/kg/hr, in 1 male and 1 female at 5 mg/kg/hr, and in 2 females at 10 mg/kg/hr. Histologically, Monastral blue pigment trapped in the walls of coronary arteries with arteriopathy was observed in the male treated with CI-1020 at 10 mg/kg/hr for 2 wk. Extramural coronary arteriopathy occurred at all doses in the 4-wk i.v. study, with higher incidence occurring in females than in males (7 of 9 treated females compared with 3 of 9 treated males). In the oral study, 1 female at 500 mg/kg/day and 1 male and 2 females at 750 mg/kg/day had coronary arteriopathy. Histological changes after 2 wk of treatment were characterized by intimal thickening, fragmentation of the internal elastic lamina, necrosis and edema of the media, and mixed inflammatory-cell infiltrates in the intima, media, and adventitia. After 4 wk of i.v. administration, arteriopathy was characterized by segmental disruption of the elastic lamina and intimal and medial fibrosis with complete replacement of smooth muscle with fibrous tissue. The adventitia was thickened as a result of fibrosis and mixed or mononuclear inflammatory-cell infiltrates. CI-1020 concentrations were higher in males (1.57 to 29 micrograms/ml) than in females (0.974 to 24.4 micrograms/ml) in the i.v. study. Transient systemic exposure with high maximum plasma concentration (Cmax) (120-352 micrograms/ml) in the oral study was insufficient to provoke arterial changes of the same magnitude as those noted with continuous i.v. administration. The regeneration of the media by fibrous tissue and the disruption of the elastic lamina may weaken the arterial wall and increase the susceptibility of the artery to the development of aneurysm.

Quantitative determination of Ecteinascidin 743 in human plasma by miniaturized high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A method was developed for the bio-analysis of Ecteinascidin 743 (ET-743) using miniaturized liquid chromatography (LC) coupled to an electrospray ionization sample inlet (TurbolonSpray) and two quadrupole mass analyzers (LC/ESI-MS/MS). Solid-phase extraction was used as a sample pretreatment procedure. Ecteinascidin 743 is a very potent anticancer compound and is administered in microgram m-2 dosages, which demands special requirements in terms of sensitivity for the analytical method supporting clinical pharmacokinetic studies. Using conventional LC/UV, a lower limit of quantitation (LLQ) of 1 ng ml-1 plasma was reached using a 500 microliters sample volume, but LC/ESI-MS/MS permitted an LLQ of 10 pg ml-1. The latter method was found to be accurate and precise, and provided a broad linear concentration range of 0.010-2.50 ng ml-1.

Increase in insulin action and fat oxidation after treatment with CL 316,243, a highly selective beta3-adrenoceptor agonist in humans

Stimulation of beta3-adrenoceptors by selective agonists improves insulin action and stimulates energy metabolism in various rodent models of obesity and type 2 diabetes. Whether selective beta3-adrenoceptor stimulation exerts metabolic actions in humans remains to be proven. The effects of a highly selective beta3-adrenoceptor agonist on insulin action, energy metabolism, and body composition were assessed in 14 healthy young lean male volunteers (age 22.5 +/- 3.3 years, 15 +/- 5% body fat [mean +/- SD]) randomly assigned to 8 weeks of treatment with either 1,500 mg/day of CL 316,243 (n = 10) or placebo (n = 4). Insulin-mediated glucose disposal (IMGD), nonoxidative glucose disposal (NOGD), oxidative glucose disposal (OGD) (indirect calorimetry), and splanchnic glucose output (SGO; beta3-[H3]glucose) were determined during a 100-min hyperinsulinemic-euglycemic glucose clamp (40 mU x m(-2) x min(-1)) before and after 4 and 8 weeks of treatment. The 24-h energy expenditure (24-EE), 24-h respiratory quotient (24-RQ), and the oxidation rates of fat and carbohydrate were determined in a respiratory chamber before and after 8 weeks. After 4 weeks, treatment with CL 316,243 increased IMGD (+45%, P < 0.01) in a plasma concentration-dependent manner (r = 0.76, P < 0.02). This effect was due to an 82% increase in NOGD (P < 0.01), while OGD and SGO remained unchanged. The effects on insulin action were markedly diminished after 8 weeks; this was significantly related to an unexpected decline in the plasma concentrations of CL 316,243 (-36%, P = 0.08). At this time, 24-RQ was lowered (P < 0.001), corresponding to a 23% increase in fat oxidation (P < 0.01) and a 17% decrease in carbohydrate oxidation (P = 0.05). The 24-EE after 8 weeks did not differ from baseline, and there was no change in body weight or body composition. Plasma concentrations of glucose, insulin, and leptin were unaffected by treatment, while free fatty acid concentrations increased by 41% (P < 0.05), again linearly with the achieved plasma concentration of CL 316,243 (r = 0.67, P < 0.05). Treatment with CL 316,243 had no effect on heart rate or blood pressure and caused no cases of tremors. We conclude that treatment of lean male subjects with CL 316,243 increases insulin action and fat oxidation, both in a plasma concentration-dependent manner. This is the first study to demonstrate unequivocal metabolic effects of a highly selective beta3-adrenoceptor agonist in humans.

Analysis of Ecteinascidin 743, a new potent marine-derived anticancer drug, in human plasma by high-performance liquid chromatography in combination with solid-phase extraction

A reversed-phase high-performance liquid chromatographic method has been developed and validated for the quantification of the novel anticancer drug Ecteinascidin 743 in human plasma. The sample pretreatment of the plasma samples involved a solid-phase extraction (SPE) on cyano columns. Propyl-p-hydroxybenzoate was added after the sample pretreatment to correct for variability in injection volumes. The separation was performed on a Zorbax SB-C18 column (75x4.6 mm I.D., particle size 3.5 microm) with acetonitrile-25 mM phosphate buffer, pH 5.0 (70:30, v/v) as the mobile phase. The flow-rate was 1.0 ml/min and the eluent was monitored at 210 nm. The accuracies and precisions of the assay fall within +/-15% for all quality control samples and within +/-20% for the lower limit of quantitation, which was 1.0 ng/ml using 500 microl of plasma. The overall recovery of the sample pretreatment procedure for Ecteinascidin 743 was 87.0+/-5.9%. The drug was found to be stable in human plasma at -30 degrees C for at least 2 months. At room temperature Ecteinascidin 743 was stable in human plasma for 5 h at most.

Sesamolin inhibits lipid peroxidation in rat liver and kidney

Although the sesame lignans, sesaminol and sesamolinol, have been shown to possess antioxidative activity, less is known about the metabolism and antioxidative properties of sesamolin, a major constituent of sesame oil. To determine the ability of sesamolin to act as an antioxidant in vivo, we fed rats a diet containing 1% sesamolin for 2 wk and studied its metabolism and its effects on oxidative stress. About 75% of the ingested sesamolin was excreted unmetabolized in feces, but it was not detected in urine. Sesamolin and its metabolites, sesamol and sesamolinol, were excreted primarily as sulfates and glucuronides. The amount of sesamolin and its metabolites was lower in the plasma than in the liver or kidneys. When we compared rats fed a diet containing 1% sesamolin for 14 d with those fed a control diet, we found that liver weight was significantly greater in the former group. Lipid peroxidation activity, measured as 2-thiobarbituric acid reactive substances, was significantly lower in the kidneys and liver of the sesamolin-fed rats than in the controls. In addition, the amount of 8-hydroxy-2'-deoxyguanosine excreted in the urine was significantly lower in the sesamolin-fed rats. These results suggest that sesamolin and its metabolites may contribute to the antioxidative properties of sesame seeds and oil and support our hypothesis that sesame lignans reduce susceptibility to oxidative stress.

Effect of 5-[3-[((2S)-1,4-benzodioxan-2-ylmethyl)amino]propoxy]-1,3-benzodioxole HCl (MKC-242), a novel 5-HT1A-receptor agonist, on aggressive behavior and marble burying behavior in mice

Behavioral effects of 5-[3-[((2S)-1,4-benzodioxan-2-ylmethyl)amino]propoxy]-1,3-be nzodioxole HCl (MKC-242), a novel 5-HT1A-receptor agonist, were evaluated using animal models of anxiety and obsessive compulsive disorder and compared against reference compounds. MKC-242 suppressed foot shock-induced fighting behavior without loss of motor coordination in mice as the reference compounds did. The ED50 values of MKC-242, buspirone, tandospirone and diazepam were 1.7, 42, 80 and 2.0 mg/kg, p.o., respectively. The duration of the suppression of fighting by MKC-242 was longer than those of buspirone and tandospirone and comparable to that of diazepam. Similar results were also obtained with the water-lick conflict test in rats. The plasma concentration of MKC-242 in rats was much higher than the reported value of buspirone during 0.25-6 hr after oral administration. In addition, MKC-242 reduced marble burying behavior without reduction of motor activity. Fluoxetine, tandospirone and diazepam also reduced the behavior at non-sedative doses. These findings indicate that MKC-242 possesses a longer-lasting anxiolytic effect than azapirones. This might be due to the high concentration of the compound in plasma. In addition, it is also suggested that MKC-242 possesses an antiobsessional effect.

Evidence that a positive modulator of AMPA-type glutamate receptors improves delayed recall in aged humans

Elderly subjects (65-76 years) were tested for recall of nonsense syllables prior to and after oral administration of 1-(quinoxalin-6 ylcarbonyl)piperidine (CX516), a centrally active drug that enhances currents mediated by AMPA-type glutamate receptors. A significant and positive drug effect was found for delayed (5 min) recall at 75 min posttreatment; average scores for the highest dose group were more than twofold greater than for the placebo group. The drug had no evident influence on heart rate or self-assessment of several psychological variables.

Effects of endothelin ETA receptor antagonism with PD 156707 on hemodynamics and renal vascular resistance in rabbits

The objective of this study was to determine the in vivo effectiveness of the selective endothelin ETA receptor antagonist PD 156707 (sodium 2-benzo[1,3]dioxol-5-yl-4-(4-methoxy-phenyl)-4-oxo-3-(3,4,5-trimet hoxy- benzyl)-but-2-enoate). Effectiveness was defined by the ability of the compound to block increases in renal vascular resistance and mean arterial blood pressure induced by an intravenous bolus of 0.3 nmol/kg of human endothelin-1 in pentobarbital anesthetized rabbits. Different groups of rabbits received hour long intravenous infusions of PD 156707 at doses of 0.003, 0.01, 0.03 or 0.3 mg/kg per h. During baseline conditions, mean arterial blood pressure, heart rate, renal blood flow, and renal vascular resistance were similar among the groups. The intravenous bolus of endothelin-1 significantly decreased mean arterial blood pressure (82 +/- 3 mmHg to 65 +/- 3 mmHg, P < 0.05) and increased renal vascular resistance (2.8 +/- 0.3 mmHg/ml per min to 9.2 +/- 1.1 mmHg/ml per min, P < 0.05) in untreated control animals. At doses of 0.3 and 0.03 mg/kg per h, PD 156707 virtually abolished endothelin-1 induced increases in renal vascular resistance, but did not affect the endothelin-1 induced decrease in mean arterial blood pressure. At 0.01 and 0.003 mg/kg per h, PD 156707 also inhibited endothelin-1 induced increases in renal vascular resistance but the effects were less striking, leading to the conclusion that the minimum effective intravenous dose of the compound in rabbits is in the range of 0.01-0.03 mg/kg per h. The results of this study demonstrate that PD 156707 is an extremely potent and highly selective endothelin ETA receptor antagonist. In addition, this study demonstrates the utility of renal vascular resistance as an in vivo bioassay for evaluating the selective vascular effects of endothelin receptor antagonists in this species.

Effects of an orally effective endothelin-A receptor antagonist in dogs with pacing-induced heart failure

Endothelin-1 (ET-1) is a potent vasoconstrictor that has been shown to be elevated in the plasma of humans and animals with heart failure (HF). The role of an increase in endothelin in the setting of chronic HF is not known.

METHODS

The present study was designed to determine the hemodynamic effects of a novel ET-A antagonist (PD-156,707) on the development of HF in dogs subjected to chronic ventricular tachycardia. Thirteen dogs were chronically instrumented to measure cardiac output (CO), left ventricular pressure (LVP), left atrial pressure (LAP), and arterial pressure (MAP). They were then paced at 210 bpm for 3 weeks and then at 245 bpm for 1 week (4th week). Two groups of dogs were studied, placebo group and a group of dogs administered the PD-156,707 compound (750 mg) orally three times per day beginning one day prior to the initiation of pacing. Hemodynamic measurements were made every three to four days during the four week pacing regimen. Arterial and venous blood samples were also taken to determine the plasma levels of endothelin-1 and PD-156-707.

RESULTS

Endothelin-1 in plasma increased in all dogs with pacing induced HF (placebo control 1.57 +/- 0.5 vs placebo HF 2.2 +/- 0.6 pg/ml and drug control 1.5 +/- 0.16 v.s. drug HF 14.6 +/- 3.8 pg/ml [p < 0.05]). Left ventricular end diastolic pressure (LVEDP) and LAP were equivalently and significantly elevated in both groups (p < 0.001) and LV dp/dt was significantly reduced (p < 0.001) in both groups 4 weeks after pacing. CO was slightly, but not significantly reduced after four weeks in both groups of dogs. However, administration of PD-157,707 significantly and profoundly reduced MAP at all times after 3 days of pacing (placebo HF[week 4]: 83.9 +/- 4.0 mmHg v.s. drug HF [week 4]: 72.4 +/- 2.3 mmHg [p < 0.05]) and total peripheral resistance (p < 0.05) at each time period following the induction of pacing.

CONCLUSION

These data indicate that ETA blockade reduces afterload early during the development of chronic HF implicating endothelin-1 as an early compensatory hormone in HF. These results also suggest that blocking the ET-A receptor may have a role as an afterload reducer in the setting of human congestive heart failure.

Pharmacokinetics and metabolism of zamifenacin in mouse, rat, dog and man

1. Zamifenacin was rapidly metabolized in vitro by liver microsomes from rat, dog, and man. 2. Zamifenacin exhibited extensive plasma protein binding with human plasma showing 20 and 10-fold higher binding that that in rat and dog respectively. 3. Following oral administration to animals, metabolic clearance resulted in decreased bioavailability due to first-pass metabolism in rat and mouse. Oral clearance in man was low as a result of increased metabolic stability and increased plasma protein binding compared with animals. 4. Metabolism was the major route of clearance of zamifenacin with the primary metabolic step resulting in opening of the methylenedioxy ring to yield the catechol. In man, this metabolite was excreted as the glucuronide conjugate, whereas in the animal species it was further metabolized by mono-methylation of the catechol.

Liquid chromatographic assay for a butenolide endothelin antagonist (PD 156707) in plasma

A sensitive and selective liquid chromatographic assay for determining the non-peptide endothelin A receptor antagonist PD 156707 (I) in rat plasma has been developed and validated. The analyte was isolated from matrix by solid-phase extraction. Liquid chromatographic separation was achieved isocratically on a 3.2 mm I.D., ODS column with a mobile phase of acetonitrile-ammonium phosphate (50 mM, pH 3.5) (44:56, v/v). Column effluent was monitored fluorometrically. Peak-height ratios (analyte/IS) were proportional to I concentrations in rat plasma from 25 to 1000 ng/ml. Assay precision and accuracy for I, based on quality controls, was 9.5% relative standard deviation, with relative error of +/- 6.5%. The quantitation limit was 25 ng/ml for a 200-microliters sample aliquot.

Psychological effects of a drug that facilitates brain AMPA receptors

The effects of 1-(quinoxalin-6-ylcarbonyl)piperidine (CX516), a centrally active compound that facilitates AMPA receptor-mediated synaptic responses, were tested in human subjects. Separate tests of delayed recall were given prior to and nearly 3 h after administration of placebo (n = 12) or drug (n = 36). Control subjects exhibited poorer performance in the second session than in the first while subjects given 600-1200 mg of the drug did not. There were no pre- vs post-treatment differences in immediate recall in either group. The drug did not reliably affect self-assessment scores for any of several psychological variables but did disrupt the normally present correlations for within-subject changes in the variables. These results suggest that AMPA receptor modulators may (1) improve memory under some circumstances and (2) produce psychological effects that are subtle or not related to specific mood states.

Inhibition of cholesterol absorption and synthesis in rats by sesamin

The effects of sesamin, a lignan from sesame oil, on various aspects of cholesterol metabolism were examined in rats maintained on various dietary regimens. When given at a dietary level of 0.5% for 4 weeks, sesamin reduced the concentration of serum and liver cholesterol significantly irrespective of the presence or absence of cholesterol in the diet, except for one experiment in which the purified diet free of cholesterol was given. On feeding sesamin, there was a decrease in lymphatic absorption of cholesterol accompanying an increase in fecal excretion of neutral, but not acidic, steroids, particularly when the cholesterol-enriched diet was given. Sesamin inhibited micellar solubility of cholesterol, but not bile acids, whereas it neither bound taurocholate nor affected the absorption of fatty acids. Only a marginal proportion (ca. 0.15%) of sesamin administered intragastrically was recovered in the lymph. There was a significant reduction in the activity of liver microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase after feeding sesamin, although the activity of hepatic cholesterol 7 alpha-hydroxylase, drug metabolizing enzymes, and alcohol dehydrogenase remained uninfluenced. Although the weight and phospholipid concentration of the liver increased unequivocally on feeding sesamin, the histological examination by microscopy showed no abnormality, and the activity of serum GOT and GPT remained unchanged. Since sesamin lowered both serum and liver cholesterol levels by inhibiting absorption and synthesis of cholesterol simultaneously, it deserves further study as a possible hypocholesterolemic agent of natural origin.