Prevention by the tachykinin NK2 receptor antagonist, SR 48968, of antigen-induced airway hyperresponsiveness in sensitized guinea-pigs.

The involvement of tachykinins in antigen-induced airway hyperresponsiveness (AHR) was characterized pharmacologically in guinea-pigs sensitized to ovalbumin with antagonists of tachykinin NK1 and NK2 receptors, namely SR 140333 and SR 48968, respectively. AHR was illustrated by increased sensitivity to bronchoconstriction provoked by aerosolized acetylcholine in anaesthetized, ventilated animals, administrated 48 h after ovalbumin aerosol challenge. SR 48968 (1 mg kg-1, i.p.), when given once 30 min before the antigen challenge, prevented AHR, whereas SR 140333 did not. These findings suggest that the tachykinin NK2 receptor antagonist, SR 48968, may be useful for investigating mechanisms of tachykinins in the development of airway hyperresponsiveness.     

Effect of the H2-Receptor Antagonist Cimetidine,on the Pharmacokinetics and Pharmacodynamics of the H1-Receptor Antagonists Hydroxyzine and Cetirizine in Rabbits

The effects of coadministration of the H₂-receptor antagonist cimetidine on the pharmacokinetics and pharmacodynamics of the H₁ receptor antagonists hydroxyzine and cetirizine were studied in rabbits. A single dose of hydroxyzine, 10 mg (Experiment A), or cetirizine, 10 mg (Experiment B), was given intravenously on three occasions: 2 weeks before cimetidine administration, after cimetidine, 100 mg/kg, had been given every 12 hr for 1 week, and 2 weeks after the cimetidine was discontinued. Serum concentrations of hydroxyzine and cetirizine, the active metabolite of hydroxyzine arising in vivo (Experiment A), or cetirizine (Experiment B) were measured by HPLC. The pharmacologic effects of hydroxyzine and cetirizine were monitored by measuring the suppression of histamine-induced wheals, using an IBM-PC and digitizer. The hydroxyzine and cetrizine half-life and AUG₀ values were significantly increased and the systemic clearance rates were significantly decreased in the presence of cimetidine. Similar results were obtained when cetirizine was administered de novo. Wheal suppression produced by hydroxyzine or cetirizine was increased and prolonged in the presence of cimetidine. The synergism observed between hydroxyzine or cetirizine and cimetidine in suppression of the histamine-induced cutaneous response may be due to a pharmacokinetic interaction.     

Postjunctional inhibitory effect of the NK2 receptor antagonist, SR 48968, on sensory NANC bronchoconstriction in the guinea-pig.

1 The effects of a selective NK2 receptor antagonist, SR 48968, on non-adrenergic non-cholinergic (NANC) bronchoconstriction in the guinea-pig were investigated in both in vitro and in vivo studies. 2 In isolated bronchus, the electrical field stimulation (EFS, 1 Hz for 1 min)-induced NANC bronchoconstriction was inhibited by 83% after preincubation with SR 48968 (10(-7) M) for 1 h. The selective NK1 receptor antagonist, CP 96,345 (10(-6) M), together with SR 48968 completely abolished the remaining EFS-evoked NANC bronchial contraction. ST 48968 (10(-7) M) totally blocked the bronchial contraction caused by neurokinin A (NKA), but reduced only slightly the bronchoconstriction caused by high concentrations of substance P (SP) and did not influence the response to acetylcholine (ACh). 3 In the guinea-pig isolated perfused lung, SR 48968 (5 x 10(-7) M) perfusion for 30 min markedly reduced, by 95% and 68% respectively, the increase in lung resistance (RL) and the decrease in dynamic compliance (CDyn) evoked by vagal stimulation (1 Hz for 1 min). Capsaicin (10(-8) M)-evoked bronchoconstriction was also significantly inhibited by SR 48968 (5 x 10(-7) M). However, the same concentration of SR 48968 did not affect the release of neuropeptide calcitonin gene-related peptide (CGRP)-like immunoreactivity (LI) evoked by either vagal stimulation or capsaicin in the isolated perfused lung, suggesting no prejunctional action.(ABSTRACT TRUNCATED AT 250 WORDS)     

The Actions of Some β-Receptor Agonists and Xanthines on Isolated Muscle Strips from the Human Oesophago-Gastric Junction

Isolated preparations from the circular muscle layer of the human oesophago-gastric junction were mounted in organ baths and isometric tension recorded. During an equilibration period, active resting tension developed suggesting that the preparations were representing the lower oesophageal sphincter. Active tension was abolished by exposing the preparations to Ca⁺⁺-free medium. The two xanthines theophylline and enprofylline almost equipotently relaxed the preparations in a concentration-dependent manner (10^-7-10^-3M). Within therapeutic concentrations, theophylline inhibited active resting tension by 30–60%, while enprofylline lowered tension by less than 20%. Inhibitory actions of adenosine were demonstrated, and this suggests that adenosine antagonism is not the mechanism of action for xanthines in the oesophagus. Non-selective β-receptor stimulation with isoprenaline inhibited active tension by 70% (10^-7M), while β₂-receptor stimulation with terbutaline inhibited tension by 47% (10^-5M). Dobutamine, believed to preferentially stimulate β₁-receptors, inhibited active tension in a concentration-dependent manner (10^-7-10^-4M). Metoprolol (10^-6M), a selective β₁-receptor antagonist, shifted the concentration-response curve for isoprenaline to the right, but left the maximal response unchanged. It is concluded that xanthines and β-receptor agonists have inhibitory actions on circular muscle from the human oesophagogastric junction. The experimental data suggest the presence of β₁- as well as β₂-receptors, both mediating inhibition of active resting tension.     

Pharmacodynamics, Pharmacokinetics, and Safety of AM211: A Novel and Potent Antagonist of the Prostaglandin D2 Receptor Type 2

The prostaglandin D(2) receptor type 2 (DP2) and its ligand, PGD(2), have been implicated in the development of asthma and other inflammatory diseases. The authors evaluated the pharmacodynamics, pharmacokinetics and safety of [2'-(3-benzyl-1-ethyl-ureidomethyl)-6-methoxy-4'-trifluoromethyl-biphenyl-3-yl]-acetic acid sodium salt (AM211), a novel and potent DP2 antagonist, in healthy participants. Single and multiple doses of AM211 demonstrated dose-dependent inhibition of eosinophil shape change in blood with near-complete inhibition observed at trough after dosing 200 mg once daily for 7 days. Maximum plasma concentrations and exposures of AM211 increased in a greater-than-dose-proportional manner after single and multiple dosing. After multiple dosing, the exposures on day 7 were higher than on day 1 with accumulation ratio values ranging from 1.4 to 1.5. Mean terminal half-life values ranged from 14 to 25 hours across the dose range of 100 to 600 mg. AM211 was well tolerated at all doses in both the single- and multiple-dose cohorts. These data support additional clinical studies to evaluate AM211 in asthma and other inflammatory diseases.     

川芎中总生物碱、总酚酸和总挥发油对大鼠离体子宫平滑肌收缩活动的抑制作用

目的:考察川芎中总生物碱、总酚酸和总挥发油对大鼠离体子宫平滑肌收缩活动的抑制作用,为阐明川芎活血调经的传统功效提供依据。方法:取大鼠离体子宫平滑肌浸泡于洛氏液中,以二甲基亚砜为空白对照、盐酸维拉帕米为阳性对照,采用Power Lab生理记录仪记录子宫平滑肌收缩曲线,通过观察收缩活动力、收缩张力变化来评价川芎中总生物碱、总酚酸(质量浓度均分别为0.025、0.05、0.1 mg/m L)和总挥发油(0.04、0.08、0.16 mg/m L)对缩宫素致大鼠离体子宫平滑肌收缩的抑制作用,并计算子宫平滑肌收缩活动力抑制率和收缩张力抑制率。结果:加入缩宫素后大鼠离体子宫平滑肌的收缩活动力、收缩张力较加入缩宫素前均显著升高(P<0.05或P<0.01),不同质量浓度3类川芎组分均可显著降低子宫平滑肌的收缩活动力、收缩张力(P<0.05或P<0.01)。与空白对照比较,除0.025 mg/m L总酚酸外,给予其余浓度药物或组分后子宫平滑肌的收缩活动力抑制率和收缩张力抑制率均显著升高(P<0.05或P<0.01)。结论:川芎中总生物碱、总酚酸和总挥发油对缩宫素致大鼠离体子宫平滑肌收缩均有一定的抑制作用,这为川芎活血调经的用法提供了参考依据。     

Role of Prasugrel, a Novel P2Y12 Receptor Antagonist, in the Management of Acute Coronary Syndromes

Prasugrel is a new P2Y₁₂ receptor antagonist that has been investigated for the treatment of atherothrombosis in patients with cardiovascular disease undergoing percutaneous coronary intervention (PCI). Similar to other thienopyridines, prasugrel is a prodrug that requires biologic conversion to active metabolites. Studies have demonstrated the ability of prasugrel to selectively and irreversibly inhibit ADP-induced platelet aggregation to a greater degree than clopidogrel. In a large randomized, double-blind, double-dummy clinical trial, it was demonstrated that treatment with prasugrel (n=6813; 60mg loading dose followed by 10 mg/day) significantly reduced the incidence of a composite endpoint of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke during the median follow-up of 14.5 months, compared with clopidogrel (n=6795; 300mg loading dose followed by 75 mg/day) in patients with acute coronary syndromes scheduled to undergo PCI. The number of patients who would need to be treated with prasugrel instead of clopidogrel in order to prevent one primary efficacy outcome was 46. Landmark analyses found that prasugrel not only reduced the incidence of individual clinical endpoints and stent thrombosis during the loading dose phase (randomization to 3 days), but also that these benefits continued throughout the maintenance phase (from 3 days until the end of the trial). Nonsurgical-related Thrombolysis In Myocardial Infarction (TIMI)-major and life-threatening bleeds were significantly more frequent in patients receiving prasugrel compared with clopidogrel. Patients with a history of stroke or transient ischemic attack (TIA) seem to be at especially high risk for bleeding, as well as patients aged >75 years and those weighing <60kg. A prespecified analysis of net clinical benefit, which took into account the effects on both the primary efficacy and safety endpoints, was conducted. After taking into account the higher bleeding rates, the net clinical benefit still favored prasugrel use compared with clopidogrel. However, patients with prior stroke or TIA, patients older than 75 years, and patients weighing <60kg did not demonstrate a net clinical benefit with prasugrel use. Prasugrel was approved for use in Europe by the European Commission in February 2009, and is currently available in the UK. In July 2009, the US Food and Drug Administration (FDA) approved the use of prasugrel for the reduction of thrombotic cardiovascular events (including stent thrombosis) in patients with acute coronary syndrome who are to be managed with PCI.     

A Semi-mechanistic Model for the Effects of a Novel Glucagon Receptor Antagonist on Glucagon and the Interaction Between Glucose,Glucagon, and Insulin Applied to Adaptive Phase II Design

A potent novel compound (MK-3577) was developed for the treatment of type 2 diabetes mellitus (T2DM) through blocking the glucagon receptor. A semi-mechanistic model was developed to describe the drug effect on glucagon and the interaction between glucagon, insulin, and glucose in healthy subjects (N = 36) during a glucagon challenge study in which glucagon, octreotide (Sandostatin), and basal insulin were infused for 2 h starting from 3, 12, or 24 h postdose of a single 0–900 mg MK-3577 administration. The drug effect was modeled by using an inhibitory E_max model (I_max = 0.96 and IC₅₀ = 13.9 nM) to reduce the ability of glucagon to increase the glucose production rate (GPROD). In addition, an E_max model (E_max = 0.79 and EC₅₀ = 575 nM) to increase glucagon secretion by the drug was used to account for the increased glucagon concentrations prechallenge (via compensatory feedback). The model adequately captured the observed profiles of glucagon, glucose, and insulin pre- and postchallenge. The model was then adapted for the T2DM patient population. A linear model to correlate fasting plasma glucose (FPG) to weighted mean glucose (WMG) was developed and provided robust predictions to assist with the dose adjustment for the interim analysis of a phase IIa study.KEY WORDS: glucagon challenge, glucagon receptor antagonist, glucose and insulin, modeling and simulation, type 2 diabetes     

A selective NK-2 antagonist blocks the increase of canine colonic tone and ileal contractions induced by the NK-2 selective receptor agonist, [βAla8] neurokinin A-(4–10)

Background: The regulatory roles of tachykinins in intestinal motor function may be clarified by use of novel, stable and selective antagonists of neurokinin receptors. We studied the effects of the non-peptide NK-2 receptor antagonist SR48968 on canine colonic tone under resting conditions and after stimulation by the selective NK-2 receptor agonist [βAla⁸] neurokinin A-(4–10) Methods: Experiments were performed in three conscious female dogs. Proximal colonic tone was recorded by a barostat and intraluminal pressures were recorded in the terminal ileum, 10, 15 and 20 cm orad to the ileocaecal junction. In separate experiments, and in a random sequence, dogs received an i.v. injection of the NK-2 antagonist SR48968, 10, 100, 1000 μg/kg, followed after 30 min by 2 μg/kg of the agonist [βAla⁸] neurokinin A-(4–10). Experiments were replicated twice in each dog. Results: The NK-2 agonist increased colonic tone, and SR48968 antagonized these effects in a dose-dependent fashion (Spearman's rank, r= 0.86; P < 0.01); antagonism was complete at the highest dose. SR48968 alone had no effect on colonic tone and ileal motility. When given during phase I or II of the interdigestive motor complex, [βAla⁸] neurokinin A-(4–10) increased ileal contractions: pre-treatment with SR48968 blocked this increase in ileal motility. When given during phase III, [βAla⁸] neurokinin A-(4–10) interrupted the motility front; this effect was not antagonized by SR48968. Conclusions: SR48968 antagonizes the increase in canine colonic tone and ileal motility induced by activation of NK-2 receptors. However, SR48968 by itself had no effect on the control of colonic tone and ileal motility under unstimulated conditions. SR48968 may be useful for investigating the physiological role of tachykinins on the gastrointestinal tract.     

Brevisulcenals-A1 and A2, Sulfate Esters of Brevisulcenals,Isolated from the Red Tide Dinoflagellate Karenia brevisulcata

Two different types of polycyclic ether toxins, namely brevisulcenals (KBTs) and brevisulcatic acids (BSXs), produced by the red tide dinoflagellate Karenia brevisulcata, were the cause of a toxic incident that occurred in New Zealand in 1998. Four major components, KBT-F, -G, -H, and -I, shown to be cytotoxic and lethal in mice, were isolated from cultured K. brevisulcata cells, and their structures were elucidated by spectroscopic analyses. New analogues, brevisulcenal-A1 (KBT-A1) and brevisulcenal-A2 (KBT-A2), toxins of higher polarity than that of known KBTs, were isolated from neutral lipophilic extracts of bulk dinoflagellate culture extracts. The structures of KBT-A1 and KBT-A2 were elucidated as sulfated analogues of KBT-F and KBT-G, respectively, by NMR and matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI TOF/TOF), and by comparison with the spectra of KBT-F and KBT-G. The cytotoxicities of the sulfate analogues were lower than those of KBT-F and KBT-G.     

Evaluation of the Safety,Tolerability, and Pharmacokinetic Profiles of TP0473292 (TS-161), A Prodrug of a Novel Orthosteric mGlu2/3 Receptor Antagonist TP0178894, in Healthy Subjects and Its Antidepressant-Like Effects in Rodents

BackgroundTP0473292 (the active ingredient of TS-161) is a prodrug of a novel metabotropic glutamate (mGlu) 2/3 receptor antagonist being developed for the treatment of patients with depression. This study evaluated the safety, tolerability, and pharmacokinetics of orally administered TS-161 in healthy subjects.MethodsThis was a first-in-human, phase 1, randomized, double-blind, placebo-controlled, single-ascending dose (15–400 mg TS-161) and 10-day multiple-ascending dose (50–150 mg TS-161) study in healthy subjects, conducted from June 2019 through February 2020. Plasma and urine concentrations of the prodrug and its metabolites, and cerebrospinal fluid (CSF) concentrations of the active metabolite TP0178894 were measured to evaluate the pharmacokinetic profiles after oral administration of TS-161.ResultsFollowing single and multiple doses, TP0473292 was extensively converted into its active metabolite TP0178894. Plasma concentrations of TP0178894 reached peak (C_max) within 5 hours post dose and declined with a t_1/2 <13 hours. Plasma exposures of TP0178894 increased with increasing dose. TP0178894 penetrated into CSF and reached a C_max of 9.892 ng/mL at a single dose of 100 mg, which was comparable with IC₅₀ values of antagonist activity at mGlu2/3 receptors. The most frequently observed adverse events that showed exposure-related incidence during the study were nausea, vomiting, and dizziness.ConclusionsThe mGlu2/3 receptor antagonist prodrug TP0473292 is safe and well-tolerated, is orally bioavailable in humans with extensive conversion into the active metabolite TP0178894 with sufficient CSF penetration to exert the anticipated pharmacological effects, and is a promising candidate for further clinical development in treatment of patients with depression.     

Characterisation of the atypical β-adrenoceptor in rabbit isolated jejunum using BRL 37344, cyanopindolol and SR 59230A

1 The present study was carried out to further investigate the nature of the β-adrenoceptor in rabbit jejunum using BRL 37344, a selective β₃-adrenoceptor agonist, cyanopindolol, a β-adrenoceptor antagonist with blocking activity at β₃-adrenoceptors and SR 59230A, a new selective β₃-adrenoceptor antagonist. 2 Isoprenaline produced a concentration-dependent inhibition of the spontaneous contractions of rabbit jejunum with a pD₂ of 7.14. Propranolol (1 μm ) shifted the isoprenaline concentration-response curve (CRC) to the right with a concentration-ratio of 5.85, considerably less than would be expected for an action at classical β-adrenoceptors (estimated pA₂ 6.66). 3 BRL 37344 also produced a concentration-dependent inhibition of spontaneous contractions with a pD₂ of 7.41. The BRL 37344 CRC was unaffected by propranolol (1 μm ). 4 In the presence of propranolol (1 μm ), cyanopindolol (1 μm ) shifted the isoprenaline CRC to the right (concentration-ratio of 21). Cyanopindolol also shifted the BRL 37344 CRC to the right (concentration-ratio of 38). These shifts are consistent with the affinity of cyanopindolol for β₃-adrenoceptors (estimated pA₂ values of 7.27 and 7.38 against isoprenaline and BRL 37344, respectively). 5 In the presence of propranolol (1 μm ), SR 59230A produced a concentration-dependent rightward shift of the isoprenaline CRC. The Schild plot gave a pA₂ value of 7.16, although the slope of the regression line was significantly different from unity (0.65). SR 59230A also produced a concentration-dependent shift of the BRL 37344 CRC. The Schild plot gave a pA₂ of 7.58 with the slope of the regression line not significantly different from unity (0.81). 6 The presence of β₃-adrenoceptors mediating relaxation of spontaneous contractions in rabbit jejunum is supported by the relatively poor antagonism of isoprenaline by propranolol, the relaxant effect of BRL 37344 and the antagonism of isoprenaline and BRL 37344 by cyanopindolol and SR 59230A. The lack of simple competitive antagonism of isoprenaline, but not BRL 37344, by SR 59230A may suggest more than one population of atypical β-adrenoceptor.     

The role of serotonin-2 (5-HT2) and dopamine receptors in the behavioral actions of the 5-HT2A/2C agonist, DOI, and putative 5-HT2C inverse agonist, SR46349B

Rationale

Atypical antipsychotic efficacy is often attributed to actions at serotonin-2 (5-HT₂) and dopamine receptors, indicating a potential benefit of understanding the interplay between these systems. Currently, it is known that 5-HT₂ receptors modulate dopamine release, although the role of specific dopamine receptors in 5-HT₂-mediated behavior is not well understood.

Objectives

We examined the role of 5-HT_2A, 5-HT_2C, and dopamine (D1 and D2) receptors in the behavioral response to a 5-HT_2A/2C agonist (DOI) and 5-HT_2A/2C antagonist (SR46349B).

Materials and methods

Effects were assessed by measuring rabbit head bobs (previously characterized as 5-HT_2A receptor-mediated) and body shakes (5-HT_2C-mediated).

Results

As expected, DOI produced head bobs and body shakes, and these DOI-elicited behaviors were attenuated by the SR46349B pretreatment. Unexpectedly, SR46349B also induced head bobs when administered alone. However, SR46349B-elicited head bobs are distinguishable from those produced by DOI since the 5-HT_2A antagonist, ketanserin, only attenuated DOI-elicited head bobs. Conversely, 5-HT_2C ligands (SB242084 and SB206553) inhibited SR46349B but not DOI-induced head bobs. Furthermore, when administered alone, SB206553 (a 5-HT_2C inverse agonist) produced head bobs, indicating the behavior can be either 5-HT_2A or 5-HT_2C mediated. Next, it was revealed that D1 and D2 receptors play a role in DOI-elicited head bobs, but only D1 receptors are required for SR46349B-elicited head bobs.

Conclusions

5-HT_2A receptor agonism and 5-HT_2C inverse agonism produce the same behavior, likely due to similar downstream actions at D1 receptors. Consequently, 5-HT_2C agonism or D1 agonism may be effective therapies for disorders, such as schizophrenia, currently being treated with 5-HT_2A antagonists.     

The cannabinoid CB1 receptor antagonist SR 141716A reverses the antiemetic and motor depressant actions of WIN 55, 212-2.

The dibenzopyran cannabinoids (delta-9 (Delta9)-tetrahydrocannabinol and nabilone) are clinically used to suppress nausea and vomiting produced by chemotherapeutic agents such as cisplatin. The purpose of this investigation was to investigate the antiemetic potential of the aminoalkylindole cannabinoid receptor agonist WIN 55, 212-2 [R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl) methyl] pyrolol [1,2,3-de]-1,4-benzoxazin-yl]-(1-naphthalenyl) methanone mesylate] against cisplatin-induced vomiting. Different doses of WIN 55, 212-2 (0, 1, 2.5 and 5 mg/kg, i.p.) reduced both the frequency of cisplatin (20 mg/kg, i.p.)-induced emesis (ID(50)=0.5 mg/kg) as well as the percentage of shrews vomiting (ID50=1.2 mg/kg) in a dose-dependent manner. Significant reductions in emesis frequency occurred from 2.5 mg/kg dose of WIN 55, 212-2, whereas significant total protection from vomiting was afforded at its 5 mg/kg dose. The antiemetic actions of a 5-mg/kg dose of WIN 55, 212-2 against cisplatin (20 mg/kg, i.p.)-induced vomiting were reversed by nonemetic subcutaneous doses (0, 0.25, 0.5 and 1 mg/kg) of the cannabinoid CB1 receptor antagonist/inverse agonist SR 141716A [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide] (ID50=0.27 and 0.47 mg/kg, respectively) but not by a 5-mg/kg dose of the cannabinoid CB2 receptor antagonist SR 144528 [N-[(1S)-endo-1,3,3-trimethylbicyclo [2.2.1] heptan-2-yl]5-(4-chloro-3-methylphenyl)-1-(4-methybenzyl) pyrazole-3-carboxamide]. The effects of the cited doses of WIN 55, 212-2 were also investigated on several motor parameters (spontaneous locomotor activity, duration of movement and rearing frequency). Significant reductions in motor parameters were only observed at its highest tested dose (ID50=1.97, 2.75 and 2.8 mg/kg; respectively). SR 141716A (0, 0.5, 1, 5 and 10 mg/kg) also reversed the motor suppressant effects of a 5-mg/kg dose of WIN 55, 212-2 (ID50=0.39, 0.1 and 0.3 mg/kg, respectively) and significant reversals were seen from its 0.5 and 1 mg/kg doses. These results suggest that WIN 55, 212-2 reduces both emesis and indeces of locomotion via the stimulation of cannabinoid CB1 receptors. However, cannabinoid CB1 receptors in different loci are most likely responsible for the antiemetic and motor suppressive effects of WIN 55, 212-2 since reduction in the frequency of vomiting occurred at lower doses relative to its sedative actions.     

ATP-Dependent Transport of a Novel Thromboxane A2 Receptor Antagonist, [2-(4-Chlorophenylsulfonylaminomethyl)-Indan-5-yl]Acetate (Z-335) and Its Xenobiotic Taurine Conjugate (Z-335-Tau) by Rat Bile Canalicular Membrane Vesicles

PURPOSE: The characteristics of bile canalicular transport processes for xenobiotic taurine conjugates have not yet been clarified. To elucidate the biliary excretion characteristics of xenobiotic taurine conjugates, we investigated the transport of a novel thromboxane A2 receptor antagonist, Z-335, and its taurine conjugate (Z-335-Tau) across the bile canalicular membrane. METHODS: We examined the uptake of Z-335 and Z-335-Tau by isolated bile canalicular membrane vesicles (CMVs) from Sprague Dawley and Eisai-hyperbilirubinemic rats (EHBRs) which EHBRs have a hereditary defect of canalicular multidrug resistance-associated protein 2 (Mrp2) function. Also, the in vitro and in vivo kinetics of Z-335-Tau uptake and excretion were compared. RESULTS: Z-335 uptake by CMVs from normal rats exhibited marked ATP-dependence, whereas ATP-dependent uptake of Z-335 into CMVs from EHBRs was not observed. In contrast, Z-335-Tau uptake into CMVs from both normal rats and EHBRs was ATP dependent. The initial uptake velocity was concentration-dependent, with an in vitro Michaelis constant for initial uptake of 189 microM, which was similar to the in vivo value. CONCLUSIONS: The biliary excretion of Z-335 involves Mrp2, whereas that of Z-335-Tau involves active transport systems that remain intact in EHBRs and show marked ATP dependence, which ATP-dependent transport is involved in the biliary excretion of Z-335-Tau in vivo.     

Identification of the Molecular Determinants of the Antibacterial Activity of LmutTX,a Lys49 Phospholipase A2 Homologue Isolated from Lachesis muta muta Snake Venom (Linnaeus, 1766)

Snake venom phospholipases A₂ (PLA₂s) are responsible for numerous pathophysiological effects in snakebites; however, their biochemical properties favour antimicrobial actions against different pathogens, thus constituting a true source of potential microbicidal agents. This study describes the isolation of a Lys49 PLA₂ homologue from Lachesis muta muta venom using two chromatographic steps: size exclusion and reverse phase. The protein showed a molecular mass of 13,889 Da and was devoid of phospholipase activity on an artificial substrate. The primary structure made it possible to identify an unpublished protein from L. m. muta venom, named LmutTX, that presented high identity with other Lys49 PLA₂s from bothropic venoms. Synthetic peptides designed from LmutTX were evaluated for their cytotoxic and antimicrobial activities. LmutTX was cytotoxic against C2C12 myotubes at concentrations of at least 200 μg/mL, whereas the peptides showed a low cytolytic effect. LmutTX showed antibacterial activity against Gram‐positive and Gram‐negative bacteria; however, S. aureusATCC 29213 and MRSA strains were more sensitive to the toxin's action. Synthetic peptides were tested on S. aureus, MRSA and P. aeruginosaATCC 27853 strains, showing promising results. This study describes for the first time the isolation of a Lys49 PLA₂ from Lachesis snake venom and shows that peptides from specific regions of the sequence may constitute new sources of molecules with biotechnological potential.     

A Safety Monitoring Procedure for a Clinical Drug Development Program,with Application to the Assessment of a Novel COX-2 Inhibitor

Formal safety monitoring procedures are well-developed for use in individual clinical trials and provide valuable guidance to Independent Data Monitoring Committees (IDMCs). Less has been written about procedures for use over the whole of a drug development program. It is becoming common for a single IDMC to be appointed for a whole series of studies involving a single compound. While each study will have its own goals in terms of efficacy, safety, or both, there is the potential for all of them to contribute to an emerging picture of safety. Indeed, an IDMC overseeing several studies will need to integrate the data coming from each and a formal pre-defined approach can be a valuable aid. Formal procedures are especially relevant in situations where one or two undesirable events are recognized from the outset as being of particular concern. In some cases this might be death, and in the example discussed here it is a cardiovascular event of the type that has been found to be related to certain COX-2 inhibitors. In this paper a design proposal for a safety monitoring procedure for use by an IDMC during the development of a new COX-2 inhibitor will be described.     

Inverse agonist properties of N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide HCl (SR141716A) and 1-(2-chlorophenyl)-4-cyano-5-(4-methoxyphenyl)-1H-pyrazole-3-carboxyl ic acid phenylamide (CP-272871) for the CB(1) cannabinoid receptor

Two subtypes of cannabinoid receptors are currently recognized, CB(1), found in brain and neuronal cells, and CB(2), found in spleen and immune cells. We have characterized 1-(2-chlorophenyl)-4-cyano-5-(4-methoxyphenyl)-1H-pyrazole-3-carboxyl ic acid phenylamide (CP-272871) as a novel aryl pyrazole antagonist for the CB(1) receptor. CP-272871 competed for binding of the cannabinoid agonist (3)H-labeled (-)-3-[2-hydroxy-4-(1, 1-dimethylheptyl)-phenyl]-4-[3-hydroxypropyl]cyclohexan-1-ol ([(3)H]CP-55940) at the CB(1) receptor in rat brain membranes with a K(d) value 20-fold greater than that of N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide HCl (SR141716A). CP-272871 also competed for binding with the aminoalkylindole agonist (3)H-labeled (R)-(+)-[2, 3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo[1,2,3-de]1, 4-benzoxazin-6-yl](1-naphthyl)methanone ([(3)H]WIN-55212-2), as well as the aryl pyrazole antagonist [(3)H]SR141716A. Inverse agonist as well as antagonist properties were observed for both SR141716A and CP-272871 in signal transduction assays in biological preparations in which the CB(1) receptor is endogenously expressed. SR141716A augmented secretin-stimulated cyclic AMP (cAMP) accumulation in intact N18TG2 neuroblastoma cells, and this response was reversed by the agonist desacetyllevonantradol. CP-272871 antagonized desacetyllevonantradol-mediated inhibition of adenylyl cyclase in N18TG2 membranes, and increased adenylyl cyclase activity in the absence of agonist. SR141716A and CP-272871 antagonized desacetyllevonantradol-stimulated (35)S-labeled guanosine-5'-O-(gamma-thio)-triphosphate ([(35)S]GTPgammaS) binding to brain membrane G-proteins, and decreased basal [(35)S]GTPgammaS binding to G-proteins. K(+) enhanced CP-272871 and SR141716A inverse agonist activity compared with Na(+) or NMDG(+) in the assay. These results demonstrated that the aryl pyrazoles SR141716A and CP-272871 behave as antagonists and as inverse agonists in G-protein-mediated signal transduction in preparations of endogenously expressed CB(1) receptors.