Interaction of citrus juices with pranidipine, a new 1,4-dihydropyridine calcium antagonist, in healthy subjects

OBJECTIVES: The study was conducted to investigate whether oral co-administration with citrus juices significantly affects the pharmacokinetics and/or pharmacodynamics of pranidipine, a new 1,4-dihydropyridine calcium antagonist, in healthy male subjects. Grapefruit juice and orange juice, which were both commercially available, were used in this study. METHODS: Sixteen healthy male Japanese subjects participated in this study and were divided into two groups for grapefruit juice and orange juice treatment. The study followed an open-labelled crossover design, comparing the effects of a single oral dose of 2 mg pranidipine taken together with 250 ml citrus juice or 250 ml water. Serum pharmacokinetics of pranidipine, adverse reactions, blood pressure, heart rate, 12-lead ECG, haematology, clinical chemistry and urinalysis were measured throughout the study. RESULTS: For grapefruit juice, mean Cmax and AUC0-24 h were significantly higher than those of water (P=0.0003 and 0.0005, respectively, ANOVA) with the ratios of log transformed values being 1.50 and 1.74, respectively. There were no differences in tmax and t1/2 between the juice and water treatments. A significant increase in heart rate (P=0.0240, ANOVA with repeated measurements) was observed in the juice treatment whereas there were no significant differences in systolic and diastolic blood pressure between the two treatments. For orange juice, a small decrease in mean Cmax was observed compared with water (P=0.0218, ANOVA) with the ratio being 0.86, but there was no significant difference in AUC0-24h between the two treatments. No marked differences were observed in tmax and t1/2. Oral pranidipine administration with orange juice did not affect heart rate, systolic and diastolic blood pressures or other parameters for safety evaluation. CONCLUSIONS: Oral co-administration with grapefruit juice and pranidipine was associated with increased bioavailability and changed the pharmacodynamics of pranidipine, particularly with regard to heart rate. Orange juice intake with pranidipine did not markedly affect the pharmacokinetics and no clinically significant changes were observed in the pharmacodynamics and safety evaluation.     

Influence of some quaternised 1,4-dihydropyridine derivatives on liposomes and erythrocyte membranes

1,4-Dihydropyridine derivatives possess various physiological activities but their mechanism of membranotropic action is not completely investigated yet. We have examined the membranotropic effects of 4-beta-pyridyl-1,4-Dihydropyridine derivatives containing different length alkyl chain substituent at N-quaternised 4-beta-pyridyl moiety. The results show the relation between incorporation of 1,4-dihydropyridine derivatives in the liposomal membranes and influence on bilayer fluidity. The compound with hexadecyl (C16H33) substituent in the 4-beta-pyridyl moiety possess the most pronounced incorporation ability and fluidizing effect. This compound causes the remarkable release of fluorescent probe calcein from liposomes and induces the hemolysis of human erythrocytes as well. The obtained results suggest that the length of alkyl chain at quaternized 4-beta-pyridyl moiety is significant for the expression of membranotropic effects of tested compounds.     

Cytotoxic and antitumor activity of MEN 10710, a novel alkylating derivative of distamycin

MEN 10710 is a new synthetic distamycin derivative possessing four pyrrole rings and a bis-(2-chloroethyl)aminophenyl moiety linked to the oligopyrrole backbone by a flexible butanamido chain. Its biological properties have been investigated in comparison with the structurally related compound, tallimustine (FCE24517), and the classical alkylating agent, melphalan (L-PAM). Cytotoxic potency of MEN 10710 was increased from 10- to 100-fold, as compared to tallimustine or L-PAM in murine L1210, human LoVo and MCF7 tumor cell lines. MEN 10710 was still active against L1210/L-PAM leukemic cells, while a partial cross-resistance was observed in LoVo/DX and in MCF7/DX cells selected for resistance to doxorubicin and expressing a MDR phenotype. Treatment with verapamil (VRP) reduced the resistance to tallimustine, but not to MEN 10710, in MCF7/DX cells. The cytotoxic effects reflect in vivo antitumor potency and toxicity in the treatment of human tumor xenografts. MEN 10710 was more effective in A2780/DDP, an ovarian carcinoma selected for resistance to cisplatin. On the other hand, the IC30 for inhibiting murine granulocyte/macrophage colony formation was 50 times higher for MEN 10710 than for tallimustine, suggesting a lower myelotoxic potential. In conclusion, the particular biological profile of MEN 10710 characterized by a marked cytotoxic potency, an interesting antitumor efficacy and a reduced in vitro myelosuppressive action may represent a further improvement in the rational design of a novel distamycin-related alkylating compound.     

Bimoclomol: a nontoxic, hydroxylamine derivative with stress protein-inducing activity and cytoprotective effects

Preservation of the chemical architecture of a cell or of an organism under changing and perhaps stressful conditions is termed homeostasis. An integral feature of homeostasis is the rapid expression of genes whose products are specifically dedicated to protect cellular functions against stress. One of the best known mechanisms protecting cells from various stresses is the heat-shock response which results in the induction of the synthesis of heat-shock proteins (HSPs or stress proteins). A large body of information supports that stress proteins--many of them molecular chaperones--are crucial for the maintenance of cell integrity during normal growth as well as during pathophysiological conditions, and thus can be considered "homeostatic proteins." Recently emphasis is being placed on the potential use of these proteins in preventing and/or treating diseases. Therefore, it would be of great therapeutic benefit to discover compounds that are clinically safe yet able to induce the accumulation of HSPs in patients with chronic disorders such as diabetes mellitus, heart disease or kidney failure. Here we show that a novel cytoprotective hydroxylamine derivative, [2-hydroxy-3-(1-piperidinyl) propoxy]-3-pyridinecarboximidoil-chloride maleate, Bimoclomol, facilitates the formation of chaperone molecules in eukaryotic cells by inducing or amplifying expression of heat-shock genes. The cytoprotective effects observed under several experimental conditions, including a murine model of ischemia and wound healing in the diabetic rat, are likely mediated by the coordinate expression of all major HSPs. This nontoxic drug, which is under Phase II clinical trials, has enormous potential therapeutic applications.     

Antitrypanosomal activity of a new triazine derivative, SIPI 1029, In vitro and in model infections

A recently developed diaminotriazine derivative [O,O'-bis(1, 2-dihydro-2,2-tetramethylene-4,6-diamino-S-triazin-1-yl)-1, 6-hexanediol dihydrochloride; T-46; SIPI 1029] was examined for activity against African trypanosomes in in vitro and in vivo model systems. In vitro, SIPI 1029 was 50% inhibitory for growth of bloodstream trypomastigotes of four strains of Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense at 0.15 to 2.15 nM (50% inhibitory concentrations). In in vivo mouse laboratory models of T. b. rhodesiense clinical isolate infections, SIPI 1029 was curative for 12 of 13 isolates at /=60% curative, and in six of these, a dose of /=60% cure rates. A number of these isolates were resistant to the standard trypanocide melarsoprol (Arsobal) and/or the diamidines diminazene aceturate (Berenil) and pentamidine. SIPI 1029 was also curative in combination with DL-alpha-difluoromethylornithine (Ornidyl) in a T. b. brucei central nervous system model infection. Some evidence of toxicity was found in dosage regimens of 10 mg/kg/day for 2 or 3 days in which deaths were observed in 6 of 65 animals given this dosage regimen. The activity of SIPI 1029 in this study indicates that this class of compounds (diaminotriazines) should be explored as leads for new human and veterinary trypanocides.     

Ceftezole, a new cephalosporin C derivative I. In vitro and in vivo antimicrobial activity

Ceftezole, a new cephalosporin antibiotic similar to cefazolin, has the following chemical structure: (6R,7R)-8-oxo-7[2-(1H-tetrazol-1-yl)acetamido]-3-[(1,3,4-thiadiazol-2-ylthio)methyl]-5-thia-1-azabicyclo[4.2.0]oct-2-ene-carboxylic acid. Ceftezole was found to be a broad-spectrum antibiotic, active in vitro against many species of gram-positive and gram-negative bacteria except Pseudomonas aeruginosa, Serratia marcescens and Proteus vulgaris. The activity of ceftezole against clinical isolates of Escherichia coli and Klebsiella spp. appeared to be nearly equal to that of cefazolin and higher than those of cephaloridine and cephalothin. Cross-resistance was observed between ampicillin and cephaloridine, but not between ampicillin and ceftezole, in susceptibility tests on clinical isolates of P. mirabilis. The in vitro activity was little affected by the inoculum size, the presence of human serum or the test medium. Ceftezole exhibited apparent bactericidal activity at the concentrations above the minimum inhibitory concentration (MIC) against both S. aureus and E. coli. The development in vitro of resistance by S. aureus 209p and E. coli NIHJ to ceftezole after 16 transfers was similar to or somewhat slower than that to other drugs tested. Ceftezole was relatively stable in nutrient broth and minimally degraded in the serum or tissue homogenates of rats. Ceftezole, in a single subcutaneous administration, exhibited somewhat less efficacy in mice against intraperitoneal infections with Streptococcus pyogenes, S. pneumoniae, E. coli, K. pneumoniae or P. mirabilis than either cephaloridine or cefazolin. However, ceftezole exhibited efficacy similar to that of cephaloridine or cefazolin when administered in three doses. Furthermore, ceftezole was as effective as cefazolin in the treatment of experimental abscesses in mice caused by subcutaneous inoculation with S. aureus.     

Identification of 1,4-dihydropyridine binding domains within the primary structure of the alpha 1 subunit of the skeletal muscle L-type calcium channel

Damage to the spinal cord in course of the treatment of diseases of the infrarenal aorta is a rare but calamitous complication. The reported incidence is about 0.2%. The neurological loss is usually complete flaccid paraplegia with high mortality and rare full or partial recovery. Between 1980 and 1991, 1070 reconstructive procedures of the infrarenal aorta were performed: 821 due to aneurysm (316 elective procedures [mortality 1.6%] and 505 emergency procedures [mortality 24.5%]) and 249 due to aorto-iliac occlusive disease. Damage to the spinal cord occurred in 2 patients (2/1070, 0.19%). One patient had incomplete paraparesis following repair of an unruptured abdominal aortic aneurysm with gradual return of all neurological symptoms to normal. The second patient developed complete paraplegia following repair of a ruptured infrarenal aneurysm. There war no recovery of the symptoms. The patient died from septicaemia 4 months later.     

Synthesis of a novel phosphate ester of a vitamin E derivative and its antioxidative activity

A novel phosphate ester containing a chromanol structure was synthesized from 1,2-diacyl-sn-glycero-3-phospho-2'-hydroxyethyl-2',5',7',8'-tetramethyl- 6' -hydroxychroman (PCh) by hydrolysis catalyzed by phospholipase C from Bacillus cereus. The structure of the product was found by spectral analyses to be 2-(2',5',7',8'-tetramethyl-6'-hydroxychromanyl)ethylphosphate++ + (Ch-P). Ch-P was highly soluble in the aqueous phase at neutral pH values and exerted higher antioxidative activity than alpha-tocopherol and PCh in the Fe(III)/ascorbic acid-catalyzed peroxidation of a fish oil emulsion and the autoxidation of a rat brain homogenate.     

Electrophysiological characterization of class III activity of a verapamil derivative in guinea-pig cardiac tissues

In isolated guinea-pig papillary muscle ([K+]o: 4.7 mmol/l, stimulation rate: 1 Hz) the verapamil derivative NN-bis-(3,4-dimethoxyphenethyl)-N-methylamine)-HCl (YS035; 0.3-100 mumol/l) increased the action potential duration measured at 90% repolarization level (APD90) up to 132% of control and enhanced the force of contraction (Fc) up to 125% of control while resting potential (RP) and the maximum upstroke velocity (Vmax) remained nearly unchanged. At 300 mumol/l YS 035, the membrane became depolarised and action potentials could no longer be elicited. These effects were reversed during wash-out. The increase of ADP90 was largest at 0.05 Hz, and the drug-induced effect continuously declined with an increase in stimulation frequency to 2 Hz. Control ADP90 was correlated to the absolute increase of ADP90 (r = 0.84). In atrial muscle the effect of YS 035 on APD90 was more pronounced than in papillary muscle. The Vmax of slow responses ([K+]o: 27 mmol/l, [Ba2+]o: 0.5 mmol/l) was not affected by concentrations as high as 30 mumol/l YS 035, whereas APD90 was enhanced. An increase in the stimulation rate (0.05 to 0.33 Hz) induced only a small decrease of Vmax at 100 mumol/l YS 035. According to this electrophysiological characterisation YS 035 shows Class III antiarrhythmic properties.     

In vitro and in vivo antipseudomonal activity, acute toxicity, and mode of action of a newly synthesized fluoroquinolonyl ampicillin derivative

Compounds N-(6,7-difluoroquinolonyl)-ampicillin (AU-1) and N-(6-fluoroquinolonyl)-ampicillin (FQ-1), synthesized by coupling of the carboxyl group of 6,7-difluoroquinolone (FP-3) and 6-fluoroquinolone (FP4), respectively, with the alpha-amino-group of ampicillin side chain, exhibit antipseudomonal activity similar to and lower acute toxicity than that of norfloxacin, whereas neither ampicillin nor the fluoroquinolone moieties, compound FP-3 or FP4, alone have such activity. Also, AU-1 and FQ-1 are active against tested clinical isolates of Pseudomonas aeruginosa that are highly resistant to norfloxacin, gentamicin, or both. The therapeutic efficacies of FQ-1 and norfloxacin were assessed and compared in neutropenic mice infected with a 90% lethal dose of P aeruginosa. Mice intraperitoneally administered FQ-1 (10 mg/kg) 4, 8, 24, and 48 hours after infection had survival rates as high as 80%, comparable to those of mice treated with norfloxacin at the same dosage and dosing schedule. The study of protoplast formation revealed that FQ-1 did not inhibit cell-wall biosynthesis but did induce cell filamentation of Bacillus subtilis at a level close to its minimal inhibition concentration. Both AU-1 and FQ-1 were able to intercalate into the double-stranded DNA. However, that FQ-1 lost such activity after it was treated with penicillinase suggests that the lactam-ring structure in ampicillin moiety of FQ-1 was hydrolyzed by penicillinase and that the hydrolyzed structure of FQ-1 does not own DNA-intercalation activity.     

Endotoxin and tumor necrosis factor alpha exert a similar proinflammatory effect in neonatal rat cardiomyocytes, but have different cardiodepressant profiles

Bolus application of endotoxin to healthy volunteers results in reversible hemodynamic alterations, such as observed in septic cardiomyopathy. Currently, endotoxin-induced cardiodepression is mainly attributed to the endotoxin-induced release of proinflammatory cytokines into the circulation, particularly of tumor necrosis factor alpha and interleukin-1, the serum levels of these cytokines being enhanced in sepsis and septic shock, and also in various heart diseases. In this study, we report a proinflammatory effect of endotoxin (1-10 micrograms/ml, 24-h incubation period) on neonatal rat cardiomyocytes in serum-free culture, evidenced by induction of inducible nitric oxide synthase, enhanced release of nitrite (protein synthesis-dependent) and interleukin-6 into the supernatant, as well as an increase in cell-associated interleukin-1 and a specific cardiodepressant profile: endotoxin disrupts beta-adrenoceptor-mediated increase in pulsation amplitude, but alpha-adrenoceptor-induced increase in pulsation amplitude and arrhythmias are not suppressed. In the presence of dexamethasone (0.1 microM), the endotoxin-mediated blockade of beta-adrenergic responsiveness, as well as induction of inducible nitric oxide synthase, enhanced nitrite release and interleukin-1/-6-production are inhibited. In contrast, tumor necrosis factor alpha at a low concentration (10 U/ml) depresses alpha- and beta-adrenergic responsiveness in the presence of dexamethasone in a nitric oxide-independent manner. These data suggest a stimulatory effect of endotoxin on the cardiomyocyte and a specific proinflammatory and nitric oxide-dependent cardiodepressant profile of endotoxin.     

Psammaplysin F, a new bromotyrosine derivative from a sponge, Aplysinella sp

A new member of the psammaplysin family, psammaplysin F (6) has been isolated from an undescribed species of Aplysinella sponge, along with the four known psammaplysins A-C (1-3) and E (5). The structure of psammaplysin F was determined by spectral analysis.     

Anticonvulsant activity of azirino[1,2-d][1,4]benzodiazepines and related 1,4-benzodiazepines in mice

The anticonvulsant properties of several 1,4-benzodiazepine and azirino[1,2-d][1,4]benzodiazepine (ABDZ) derivatives were studied after intraperitoneal (IP) administration in DBA/2 mice (a strain genetically susceptible to sound-induced seizures) and in Swiss mice. The anticonvulsant effects were evaluated on seizures evoked by means of auditory stimulation (109 dB, 12-16 kHz) in animals placed singly under a hemispheric Perspex dome or on seizures induced by administration of pentylenetetrazole. The 1,4-benzodiazepines were generally more potent than the related ABDZ derivatives. The rank order of potency for anticonvulsant activity was flunitrazepam > diazepam > pinazepam > ABDZ5 > ABDZ4 > prazepam > halazepam > ABDZ1 > ABDZ3 > camazepam > ABDZ6 > ABDZ2. The impairment of locomotor performance following IP administration of these derivatives was also evaluated by means of the rotarod test. The rank order of potency for impairment of coordinated motor movements was pinazepam > flunitrazepam > diazepam > ABDZ5 > prazepam > halazepam > ABDZ4 > ABDZ3 > ABDZ1 > camazepam > ABDZ2 = ABDZ6. The potency of various 1,4-benzodiazepines and ABDZs as inhibitors of specific [3H]flumazenil binding to membranes from cerebellum or cortex was evaluated. In general, ABDZs were active as anticonvulsants and inhibited [3H]flumazenil binding in the micromolar range. Radioligand binding studies carried out in stable cell lines demonstrated that none of the ABDZs tested showed a particular subtype specificity. The pharmacological actions of ABDZ4 and ABDZ5, which appeared to be the most potent ABDZs as anticonvulsants, were significantly reduced by treatment with flumazenil (8.24 mumol/kg IP), suggesting a clear involvement of benzodiazepine mechanisms in the anticonvulsant activity of these compounds or their metabolites. The anticonvulsant activity of ABDZ4 and ABDZ5 was also evaluated against seizures induced in DBA/2 mice by two beta-carbolines: methyl-beta-carboline-3-carboxylate (beta-CCM) and methyl-6,6-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM). Both ABDZ4 and ABDZ5 give better protection against seizures induced by beta-CCM than DMCM, suggesting a preferential action on the benzodiazepine receptor subtype BDZ1.     

Selective proteolytic activity of the antitumor agent kedarcidin

Kedarcidin is a potent antitumor antibiotic chromoprotein, composed of an enediyne-containing chromophore embedded in a highly acidic single chain polypeptide. The chromophore was shown to cleave duplex DNA site-specifically in a single-stranded manner. Herein, we report that in vitro, the kedarcidin apoprotein, which lacks any detectable chromophore, cleaves proteins selectively. Histones that are the most opposite in net charge to the apoprotein are cleaved most readily. Our findings imply that the potency of kedarcidin results from the combination of a DNA damaging-chromophore and a protease-like apoprotein.     

Garsubellin A, a novel polyprenylated phloroglucin derivative, increasing choline acetyltransferase (ChAT) activity in postnatal rat septal neuron cultures

Garsubellin A (1), a novel polyprenylated phloroglucin derivative, has been isolated from the wood of Garcinia subelliptica and its structure has been elucidated by spectroscopic analyses. Compound 1 could increase the ChAT activity at 10 microM in P10 rat septal neuron cultures.     

Nine L-type amino acid residues confer full 1,4-dihydropyridine sensitivity to the neuronal calcium channel alpha1A subunit. Role of L-type Met1188

Pharmacological modulation by 1,4-dihydropyridines is a central feature of L-type calcium channels. Recently, eight L-type amino acid residues in transmembrane segments IIIS5, IIIS6, and IVS6 of the calcium channel alpha1 subunit were identified to substantially contribute to 1,4-dihydropyridine sensitivity. To determine whether these eight L-type residues (Thr1066, Gln1070, Ile1180, Ile1183, Tyr1490, Met1491, Ile1497, and Ile1498; alpha1C-a numbering) are sufficient to form a high affinity 1,4-dihydropyridine binding site in a non-L-type calcium channel, we transferred them to the 1, 4-dihydropyridine-insensitive alpha1A subunit using site-directed mutagenesis. 1,4-Dihydropyridine agonist and antagonist modulation of barium inward currents mediated by the mutant alpha1A subunits, coexpressed with alpha2delta and beta1a subunits in Xenopus laevis oocytes, was investigated with the two-microelectrode voltage clamp technique. The resulting mutant alpha1A-DHPi displayed low sensitivity for 1,4-dihydropyridines. Analysis of the 1,4-dihydropyridine binding region of an ancestral L-type alpha1 subunit previously cloned from Musca domestica body wall muscle led to the identification of Met1188 (alpha1C-a numbering) as an additional critical constituent of the L-type 1,4-dihydropyridine binding domain. The introduction of this residue into alpha1A-DHPi restored full sensitivity for 1,4-dihydropyridines. It also transferred functional properties considered hallmarks of 1, 4-dihydropyridine agonist and antagonist effects (i.e. stereoselectivity, voltage dependence of drug modulation, and agonist-induced shift in the voltage-dependence of activation). Our gain-of-function mutants provide an excellent model for future studies of the structure-activity relationship of 1, 4-dihydropyridines to obtain critical structural information for the development of drugs for neuronal, non-L-type calcium channels.     

Hydrazine derivative modification of the activity of brain mitochondrial monoamine oxidases

Treatment of bovine brain stem mitochondria with hydrazine derivatives, which inhibited the monoamine oxidase activity (substrate: 5-hydroxytryptamine), was accompanied by appearance of the properties to deaminate histamine and cadaverine at a high rate. The same phenomenon was observed in vivo after treatment of mice with the hydrazine derivatives. The dramatic increase in histamine deaminating activity in brain was accompanied by a decrease in the tissue concentration of histamine. The hydrazine derivatives are considered as prooxidants stimulating via a free-radical mechanism lipid peroxidation in methyloleate solutions and in biomembranes (ref. 5) and causing qualitative alteration (transformation) in catalytic properties of monoamine oxidases of the tyre A, which acquire the histamine deaminating activity. A certain correlation was noted between the prooxidant effect of the hydrazine derivatives and the modification of catalytic properties of the membrane bound monoamine oxidases of brain mitochondria in vitro and in vivo.     

New substituted 1,4-benzoxazine derivatives with potential intracellular calcium activity

Substituted 1,4-benzoxazines bearing an amino side chain at the 2-position were prepared and were found to have a moderate activity on intracellular calcium. Of the compounds studied it was found that those which possess a homoveratrylamino moiety exhibited superior potency. The chain length and the nature of the amine (4-fluorophenylpiperazine, 4-fluorobenzhydryloxyethylamine, N-substituted homoveratrylamine) is discussed. The 4-benzyl-3, 4-dihydro-2-[3-[[2-(3,4-dimethoxyphenyl)ethyl]amino]propyl]-2H-1, 4-benzoxazine (3c) is the most potent derivative of the series with a ratio of IC50 values against PE (phenylephrine) and K+ of 2.1. Under these test conditions a ratio near 1 indicates potential intracellular calcium activity while a ratio greater than 100 an action on extracellular calcium influx.