Highly selective inhibitors of thromboxane (TX) A2 synthase were noted as a therapeutic agent for ischemic heart diseases, thromboembolic disorders, cerebral circulatory disorders, and asthma. The 1-substituted imidazoles and β-substituted pyridines showed high inhibitory potency on TXA2 synthase. The structure-activity relationships of the imidazole and pyridine derivatives as inhibitors of TXA2 synthase were investigated. Introduction of various substituents into the carboxy-bearing side chain of 1-(7-carboxyheptyl) imidazole and β-(7-carboxyheptyl) pyridine was found to increase the inhibitory potency. The length of the side chains with the phenylene group was optimum in the region of 8.5 to 10 Å for the inhibitory potency on TXA2 synthase. Amoung the tested imidazole and pyridine derivatives, (E)-4-(1-imidazolylmethyl) cinnamic acid (44) and (E)-3-[4-(3-pyridylmethyl) phenyl]-2-methylacrylic acid (56) showed the highest potency (IC50=1.1×10-8 and 3×10-9M). The inhibition by these derivatives was highly selective for TXA2 synthase, since other enzymes which are involved in the arachidonic acid cascade, such as fatty acid cyclooxygenase, 5-lipoxygenase, prostacyclin (PGI2) synthase, and PGE2 isomerase were not affected. On the basis of the results obtained from the pharmacological, physicochemical and toxicological studies on the two compounds (44 and 56), (E)-4-(1-imidazolylmethyl) cinnamic acid (44 ; OKY-046, ozagrel) was selected as the best compound of highly selective inhibitors of TXA2 synthase. The pharmacological properties of ozagrel are as follows. The inhibition of TXA2 synthase by ozagrel was more effective on human and rabbit enzymes than those of other species. Ozagrel increased 6-keto-PGF1a, one of stable metabolites of PGI2, in various isolated cells and tissues perhaps via accumulated PG endoperoxides resulted by the inhibition of TXA2 synthase. Such an increase in PGI2 production by ozagrel was also observed in various experimental animals. We obtained the suggestion that, by the reduction of TXA2 production and increment of PGI2 production, ozagrel inhibits the spasms of basilar artery and the decreases in regional cerebral blood flow in dogs which received autologous blood into cisterna magna, and inhibits the decreases in motor function and regional cerebral blood flow, and the formation of infarcted area in the animals of cerebral ischemic treatment. It was also suggested that ozagrel inhibits leukotriene-, platelet-activating factor-, and antigen-induced bronchoconstriction in guinea-pigs and inhibits the induction of airway hyperresponsiveness by various stimuli in several species of animals by both mechanisms. The summarized results of ADME, toxicological, and clinical studies were also described.
Chemistry of 1, 2, 3-triazines and their derivatives is described. This subject is focused on the authors' studies. Syntheses, structures, and electrophilic, nucleophilic, and nonionic reactions of 1, 2, 3-triazines are described. Syntheses and structures of their N-oxides and N-imines are also outlined.
The disposition of hydrophilic drugs in the central nervous system (CNS) was studied in relation to the transport properties across the brain capillaries which form the blood-brain barrier (BBB), and the choroidal epithelial cells which form the blood-cerebrospinal fluid (CSF) barrier, using β-lactam antibiotics as model compounds. The concentration profiles for cefodizime in the rat CNS were analyzed based on a pharmacokinetic model in which the physiological and anatomical aspects of the CNS were considered. The model analysis revealed that the drug penetration into the CSF after i.v. administration can be accounted for by permeation across the BBB and diffusion through the brain extracellular fluid and across the ependymal surface into the CSF. The drug molecules are eliminated from the CSF by the bulk flow and by the active transport system in the choroid plexus. In in situ and in vivo experiments, we found that the β-lactam antibiotics are transported across the BBB via a carrier-mediated mechanism. Comparison of kinetic parameters determined in vivo and in vitro experiments revealed (1) that the choroid plexus is the predominant site for the elimination of β-lactam antibiotics from the CSF and (2) that the isolated choroid plexus can be a useful tool to predict the in vivo elimination clearance. We also found that an anionic exchanger, at least in part, plays a role in the uphill transport of β-lactam antibiotics in the choroid plexus. Furthermore, the substrate specificity for the anion transporter was examined in the isolated choroid plexus. New quinolones (such as fleroxacin) are also transported by the mechanism shared by β-lactam antibiotics. Dideoxyinosine, a nucleoside derivative, can be a substrate for the transporter, whereas azidothymidine is recognized, but not transported by the transport system. Transport properties of cimetidine, a prototypic organic cation, in the choroid plexus was also characterized in vivo, in situ and in vitro experiments. An interaction was observed in the transport of cimetidine and that of organic anions. Molecular mechanisms for the CNS transport still remain to be clarified.
Neonates and leukopenic, immunosupressed patients are at high risk for severe infection of opportunistic pathogens despite of the availability of potent antimicrobial agents. In this study, antibody titers of immunoglobulin preparations (IVIG) were contrasted with the protective effect in mice against each of bacterial infection. Antibody titers were determined by ELISA. The antigens were 70-80 clinical isolates of Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus, respectively. Antibody titers of IVIG against these three gram-negative bacteria ranged 3200 to 102400. ICR mice were inoculated intraperitoneally with each of several strains against which IVIG showed various titers. IVIG showed rather high protective activities against well-reactive strains, while it showed little protective activities against poor-reactive strains. In the case of P. aeruginosa, statistical analysis of the results obtained with the antibody titer and efficacy showed a good correlation (p<0.01). On the other hand, IVIG showed a high and complicate antibody titer against S. aureus IVIG ranging 400000 to 12800000, since apparent titers contained non-specific binding of Fc portion of IgG with protein A on the cell wall. IVIG was active in mice, where protein A was less and specific binding was stronger. Bacterial cells have various components ; lipopolysaccharide, lipid A, capsule, flagella, pill, etc. that are responsive to specific antibodies. This study indicates that IVIG have such antibodies and that is associated with protective activity against bacterial infection in proportion to antibody titer.
The antiulcer activities of 59 methanol and aqueous extracts obtained from 59 crude drugs on the ethanol-HCl-induced ulceration in rats were investigated. Among them 15 extracts were selected and they were further examined for their effects on indomethacin-, aspirin- and the water-immersion stress-induced ulcer. From these results, the methanol extract of root of Iris germanica was found to show potent antiulcer activities. The above methanol extract was separated into 3 portions by solvent extration, and the ether soluble portion was fractionated into 5 fractions (1 to 5) by chromatography. Fractions 4 and 5 showed significant antiulcer activities. Fraction 4 was further purified and the obtained γ-irigermanal exhibited a potent antiulcer activity. However, further investigations are required to understand the mechanism.
It was found that γ-irigermanal, obtained from the methanol extract of root of Iris germanica, exhibited a potent antiulcer activity. Therefore, this compound was selected as a lead-compound, and related compounds were synthesized and tested for antiulcer activities. It was found that (±) ethyl 2-[2-(3-hydroxypropyl)-4-oxocyclohexylidene]-propionate (1) had excellent antiulcer activities. Then phenylpropanol derivatives, obtained by changing from cyclohexane ring of 1 to benzene ring, were synthesized and tested for antiulcer activities in order to study structure-activity relationships. As a result, (±) ethyl 2-[2-(3-hydroxypropyl)-4, 5-dimethoxyphenyl] propionate (2b) and (±) 3-[2-(3-hydroxypropyl)-4, 5-dimethoxyphenyl]-2-butanone (5) were shown to have antiulcer activities.
The sustained release mechanism of gentamicin (GM) from lactic acid/glycolic acid copolymer (PLGA) microspheres was investigated. The terminal free carboxyl group of polymer was proved to be necessary for GM to be highly incorporated into microspheres by comparing interactions with GM and two types of polymers ; free (ionized and non ionized) and the terminal esterified carboxyl group of polymer. The weight-average molecular weights (MWS) of component PLGAs of microspheres with an ionizable carboxyl group used here were approximately 4900 and 10000. The release pattern of GM was tested in phosphate buffered saline. The release rate of GM was dependent on the initial MW and surface form. The GM release continued for 20 and 30 d from PLGA 4900- and PLGA10000-microspheres, respectively. The changes of total weight of microspheres tended to decrease with time, and the molecular weight distribution of PLGA gradually shifted to lower distribution, indicating a decrease in MW. The changes and the shifts were dependent on the initial MWS of PLGAs but independent of their surface form. The half-times of wight loss of PLGA 4900- and PLGA10000-microspheres were about 10 and 20 d, respectively. From these results, the release profile of GM from PLGA microspheres was explained by the following three steps, i.e., 1) the release from the surface, 2) the relatively slow release caused by the obstruction of channels followed by the degradation of PLGA, 3) the release accompanied by the erosion of microspheres.
Using Staphylococcus aureus ISP447 strain, which shows inducible resistance to macrolide-lincosamide-streptogramin B (MLS) antibiotics, the extent of MLS-resistance induced by several macrolide antibiotics [erythromycin (EM), oleandomycin (OL), or roxithromycin (RXM)] was determined in terms of a relative ratio of a growth rate of the induced cells in the presence of a challenging drug, rokitamycin (RKM), to that of uninduced cells in the absence of RKM. The ratio was referred to as a relative inducibility (%). The inducibility was obtained at an optimum-induced condition by considering the following factors : (1) exponentially growing cells, (2) the optimum concentration of an inducer drug, i.e., 50, 150, and 150ng/ml for EM, OL, and RXM, respectively, (3) a 3-h previous incubation at 37°C in the presence of the inducer, and (4) 300 ng of RKM/ml, which is found to be optimum for induced cells to challenge, because of having no inducer activity. Using these qualification methods, inducibilities of EM, OL, and RXM as an inducer were 100.4, 27.9 and 81.1%, respectively. This method is allowed to be useful for the analysis of a structure-inducibility relationship.