Synthesis and antibacterial activity of novel and potent DNA gyrase inhibitors with azole ring

The 4-piperidyl moiety and the pyrazole ring in 1-(3-chlorophenyl)-5-(4-phenoxyphenyl)-3-(4-piperidyl)pyrazole 2, which has previously shown improved DNA gyrase inhibition and target-related antibacterial activity, were transformed to other groups and the in vitro antibacterial activity of the synthesized compounds was evaluated. The selected pyrazole, oxazole and imidazole derivatives showed moderate inhibition against DNA gyrase and topoisomerase IV with similar IC(50) values (IC(50)=9.4-25 microg/mL). In addition, many of the pyrazole, oxazole and imidazole derivatives synthesized in this study exhibited potent antibacterial activity against quinolone-resistant clinical isolates and coumarin-resistant laboratory isolates of Gram-positive bacteria with minimal inhibitory concentration values equivalent to those against susceptible strains.     

Synthesis and evaluation of 6-methylene-bridged uracil derivatives. Part 2: optimization of inhibitors of human thymidine phosphorylase and their selectivity with uridine phosphorylase

A series of novel 6-methylene-bridged uracil derivatives have been optimized for clinical use as the inhibitors of human thymidine phosphorylase (TP). We describe their synthesis and evaluation. Introduction of a guanidino or an amidino group enhanced the in vitro inhibitory activity of TP comparing with formerly reported inhibitor 1. Their selectivity for TP based on uridine phosphorylase inhibitory activity was also evaluated. Compound 2 (TPI) has been selected for clinical evaluation based on its strong TP inhibition and excellent modulation of 2'-deoxy-5-(trifluoromethyl)uridine (F(3)dThd) pharmacokinetics. As a result, TAS-102 (a combination of F(3)dThd and TPI) is currently in phase 1 clinical studies.     

Hydroxyl radical generation caused by the reaction of singlet oxygen with a spin trap, DMPO, increases significantly in the presence of biological reductants

Photosensitizers newly developed for photodynamic therapy of cancer need to be assessed using accurate methods of measuring reactive oxygen species (ROS). Little is known about the characteristics of the reaction of singlet oxygen (₁O₂) with spin traps, although this knowledge is necessary in electron spin resonance (ESR)/spin trapping. In the present study, we examined the effect of various reductants usually present in biological samples on the reaction of ₁O₂ with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The ESR signal of the hydroxyl radical (•OH) adduct of DMPO (DMPO-OH) resulting from ₁O₂-dependent generation of •OH strengthened remarkably in the presence of reduced glutathione (GSH), 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), ascorbic acid, NADPH, etc. A similar increase was observed in the photosensitization of uroporphyrin (UP), rose bengal (RB) or methylene blue (MB). Use of 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) as a spin trap significantly lessened the production of its •OH adduct (DEPMPO-OH) in the presence of the reductants. The addition of DMPO to the DEPMPO-spin trapping system remarkably increased the signal intensity of DEPMPO-OH. DMPO-mediated generation of •OH was also confirmed utilizing the hydroxylation of salicylic acid (SA). These results suggest that biological reductants enhance the ESR signal of DMPO-OH produced by DMPO-mediated generation of •OH from ₁O₂, and that spin trap-mediated •OH generation hardly occurs with DEPMPO.     

Caspase-1 and -3 mRNAs are differentially upregulated in motor neurons and glial cells in mutant SOD1 transgenic mouse spinal cord: a study using laser microdissection and real-time RT-PCR

Amyotrophic lateral sclerosis is characterized by selective motor neuron degeneration. An apoptotic pathway is thought to be involved. It is difficult, however, to analyze the molecular pathogenic mechanism in single motor neurons because of complexity in the neural tissue, which consists of multiple lineages of cells neighboring motor neurons. We quantified the caspase-1 and -3 mRNA in single motor neurons and neighboring glial cells isolated from the spinal ventral horn of mutant SOD1 transgenic (Tg) mice and littermates. Motor neurons and neighboring glial cells were isolated from spinal sections by laser microdissection, and the mRNAs were quantified by RT-PCR. In the Tg mice, caspase-1 mRNA was first upregulated in motor neurons and second in glial cells. The caspase-3 mRNA was increased in motor neurons following the caspase-1 mRNA. These results indicated that caspase-1 and -3 mRNAs are differentially upregulated in motor neurons and glial cells of the Tg mice, and that mRNAs in isolated cells can be accurately assessed using our procedures.     

Molecular cloning and expression of a second chondroitin N-acetylgalactosaminyltransferase involved in the initiation and elongation of chondroitin/dermatan sulfate

We identified a novel human chondroitin N-acetylgalactosaminyltransferase, designated chondroitin GalNAcT-2 after a BLAST analysis of the GenBank(TM) data base using the sequence of a previously described human chondroitin N-acetylgalactosaminyltransferase (chondroitin GalNAcT-1) as a probe. The new cDNA sequence contained an open reading frame encoding a protein of 542 amino acids with a type II transmembrane protein topology. The amino acid sequence displayed 60% identity to that of human chondroitin GalNAcT-1. Like chondroitin GalNAcT-1, the expression of a soluble form of the protein in COS-1 cells produced an active enzyme, which not only transferred beta1,4-N-acetylgalactosamine (GalNAc) from UDP-[(3)H]GalNAc to a polymer chondroitin representing growing chondroitin chains (beta-GalNAc transferase II activity) but also to GlcUA beta 1-3Gal beta 1-O-C(2)H(4)NHCbz, a synthetic substrate for beta-GalNAc transferase I that transfers the first GalNAc to the core tetrasaccharide in the protein-linkage region of chondroitin sulfate. In contrast, the tetrasaccharide serine (GlcUA beta 1-3Gal beta 1-3Gal beta 1-4Xyl beta 1-O-Ser) derived from the linkage region, which is an inert acceptor substrate for chondroitin GalNAcT-1, served as an acceptor substrate. The coding region of this enzyme was divided into seven discrete exons, which is similar to the genomic organization of the chondroitin GalNAcT-1 gene, and was localized to chromosome 10q11.22. Northern blot analysis revealed that the chondroitin GalNAcT-2 gene exhibited a ubiquitous but differing expression in human tissues, and the expression pattern differed from that of chondroitin GalNAcT-1. Thus, we demonstrated redundancy in the chondroitin GalNAc transferases involved in the biosynthetic initiation and elongation of chondroitin sulfate, which is important for understanding the biosynthetic mechanisms leading to the selective chain assembly of chondroitin/dermatan sulfate on the linkage region tetrasaccharide common to various proteoglycans containing chondroitin/dermatan sulfate and heparin/heparan sulfate chains.     

In vitro heparan sulfate polymerization: crucial roles of core protein moieties of primer substrates in addition to the EXT1-EXT2 interaction

Heparan, the common unsulfated precursor of heparan sulfate (HS) and heparin, is synthesized on the glycosaminoglycan-protein linkage region tetrasaccharide GlcUA-Gal-Gal-Xyl attached to the respective core proteins presumably by HS co-polymerases encoded by EXT1 and EXT2, the genetic defects of which result in hereditary multiple exostoses in humans. Although both EXT1 and EXT2 exhibit GlcNAc transferase and GlcUA transferase activities required for the HS synthesis, no HS chain polymerization has been demonstrated in vitro using recombinant enzymes. Here we report in vitro HS polymerization. Recombinant soluble enzymes expressed by co-transfection of EXT1 and EXT2 synthesized heparan polymers with average molecular weights greater than 1.7 x 105 using UDP-[3H]GlcNAc and UDP-GlcUA as donors on the recombinant glypican-1 core protein and also on the synthetic linkage region analog GlcUA-Gal-O-C2H4NH-benzyloxycarbonyl. Moreover, in our in vitro polymerization system, a part time proteoglycan, alpha-thrombomodulin, that is normally modified with chondroitin sulfate served as a polymerization primer for heparan chain. In contrast, no polymerization was achieved with a mixture of individually expressed EXT1 and EXT2 or with acceptor substrates such as N-acetylheparosan oligosaccharides or the linkage region tetrasaccharide-Ser, which are devoid of a hydrophobic aglycon, suggesting the critical requirement of core protein moieties in addition to the interaction between EXT1 and EXT2 for HS polymerization.     

Formation of superoxide anion during ferrous ion-induced decomposition of linoleic acid hydroperoxide under aerobic conditions

We studied the mechanism of formation of oxygen radicals during ferrous ion-induced decomposition of linoleic acid hydroperoxide using the spin trapping and chemiluminescence methods. The formation of the superoxide anion (O2*-) was verified in the present study. The hydroxyl radical is also generated through Fenton type decomposition of hydrogen peroxide produced on disproportionation of O2*-. A carbon-centered radical was detected using 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide (DEPMPO) as a spin trap. Alkoxyl radical formation is essential for the conversion of linoleic acid hydroperoxide into the peroxyl radical by ferrous ion. It is likely that the alkoxyl radical [R1CH(O*)R2] is converted into the hydroxylcarbon radical [R1C*(OH)R2] in water, and that this carbon radical reacts with oxygen to give the alpha-hydroxyperoxyl radical [R1R2C(OH)OO*], which decomposes into the carbocation [R1C+(OH)R2] and O2*-.     

Effects of recombinant cholera toxin B subunit on IL-1beta production by macrophages in vitro

Recombinant cholera toxin B subunit (rCTB) is a safe and potent mucosal adjuvant. As a clue to the mechanism of the adjuvant effect of rCTB, the profile of cytokines secreted in vitro by the mouse peritoneal macrophage (Mphi) treated with rCTB was examined. IL-1beta secretion, intracellular production, and expression of its mRNA of LPS-stimulated Mphi was greatly enhanced by treatment with rCTB. IL-1beta production in response to other microbial stimulators, such as Pansorbin, Sansorbin, insoluble peptidoglycan, and Taxol, was also potentiated by rCTB. Mphi pretreated with rCTB before 24 hr could maintain the ability to produce a high level of IL-1beta, suggesting that this ability may be involved in the adjuvant activity of rCTB on Mphi stimulation. The possibility of close association between rCTB and signal transduction of a Toll-like receptor family in Mphi is discussed.