Irreversible catalytic methylcyclohexane dehydrogenation by surface protonics at low temperature.

Liquid organic hydrides are regarded as promising for use as hydrogen carriers via the methylcyclohexane (MCH)-toluene-hydrogen cycle. Because of the endothermic nature of MCH dehydrogenation, the reaction is usually conducted at temperatures higher than 623 K. In this work, low-temperature catalytic MCH dehydrogenation was demonstrated over 3 wt% Pt/CeO2 catalyst by application of electric field across a fixed-bed flow reactor. Results show that a high conversion of MCH beyond thermodynamic equilibrium was achieved even at 423 K. Kinetic analyses exhibited a positive correlation of hydrogen to the reaction rates and an "inverse" kinetic isotope effect (KIE), suggesting that accelerated proton hopping with the H atoms of MCH promotes the reaction. Operando analyses and DFT calculation proved that the reverse reaction (i.e. toluene hydrogenation) was suppressed by the facilitation of toluene desorption in the electric field. The electric field promoted MCH dehydrogenation by surface proton hopping, even at low temperatures with an irreversible pathway.

Low-temperature selective catalytic dehydrogenation of methylcyclohexane by surface protonics.

The methylcyclohexane (MCH)-toluene cycle is a promising liquid organic hydride system as a hydrogen carrier. Generally, MCH dehydrogenation has been conducted over Pt-supported catalysts, for which it requires temperatures higher than 623 K because of its endothermic nature. For this study, an electric field was applied to Pt/TiO2 catalyst to promote MCH dehydrogenation at low temperatures. Selective dehydrogenation was achieved with the electric field application exceeding thermodynamic equilibrium, even at 423 K. With the electric field, "inverse" kinetic isotope effect (KIE) was observed by accelerated proton collision with MCH on the Pt/TiO2 catalyst. Moreover, Pt/TiO2 catalyst showed no methane by-production and less coke formation during MCH dehydrogenation. DRIFTS and XPS measurements revealed that electron donation from TiO2 to Pt weakened the interaction between catalyst surface and π-coordination of toluene. Results show that the electric field facilitated MCH dehydrogenation without methane and coke by-production over Pt/TiO2 catalyst.

Characterization of human cytochrome p450 enzymes involved in the metabolism of cilostazol.

Cilostazol (OPC-13013; 6-[4-(1-cyclohexl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)-quinolinone) is widely used as an antiplatelet vasodilator agent. In vitro, the hydroxylation of the quinone moiety of cilostazol to OPC-13326 [6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-4-hydroxy-2(1H)-quinolinone], is the predominant route, and the hydroxylation of the hexane moiety to OPC-13217 is the second most predominant route. This study was carried out to identify and kinetically characterize the human cytochrome P450 (P450) isozymes responsible for the formation of the two major metabolites of cilostazol, namely, OPC-13326 and OPC-13217 [3,4-dihydro-6-[4-[1-(cis-4-hydroxycyclohexyl)-1H-tetrazol-5-yl)butoxy]-2(1H)-quinolinone)]. In in vitro studies using 14 recombinant human P450 isozymes, CYP1A1, CYP1A2, CYP1B1, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP2J2, CYP3A4, CYP3A5, and CYP4A11, cilostazol was metabolized to OPC-13326 mainly by CYP3A4 (K(m) = 5.26 muM, intrinsic clearance (CL(int)) = 0.34 microl/pmol P450/min), CYP1B1 (K(m) = 11.2 microM, CL(int) = 0.03 microl/pmol P450/min), and CYP3A5 (K(m) = 2.89 microM, CL(int) = 0.05 microl/pmol P450/min) and to OPC-13217 mainly by CYP3A5 (K(m) = 1.60 microM, CL(int) = 0.57 microl/pmol P450/min), CYP2C19 (K(m) = 5.95 microM, CL(int) = 0.16 microl/pmol P450/min), CYP3A4 (K(m) = 5.35 microM, CL(int) = 0.10 microl/pmol P450/min), and CYP2C8 (K(m) = 33.8 microM, CL(int) = 0.009 microl/pmol P450/min). The present study showed that the two major metabolites of cilostazol in vitro, namely, OPC-13326 and OPC-13217, are mainly catalyzed by CYP3A4 and CYP3A5, respectively.

Molecular-based haplotype analysis of the beta 2-adrenergic receptor gene (ADRB2) in Japanese asthmatic and non-asthmatic subjects.

BACKGROUND: The beta2-adrenergic receptor gene (ADRB2) is a target molecule of beta2-agonists. Single nucleotide polymorphisms (SNPs) in the ADRB2 are related to the effectiveness of beta2-agonists. However, there are some discrepancies in the results of pharmacogenetic studies of ADRB2 among different ethnic groups. The aims of this study were to determine the ADRB2 haplotypes and diplotypes in Japanese asthmatic and non-asthmatic subjects and to examine their relation to asthma and to compare these results with previous studies done in other ethnic groups. METHODS: Complete sequences for 3 kb promoter and 1.2 kb structural regions of ADRB2 were analyzed in 48 Japanese asthmatics and 100 controls, and haplotypes and diplotypes of SNPs were analyzed. RESULTS: Fifteen SNPs including a novel one in -839 were observed. Allele frequencies for all SNPs were similar between asthmatics and controls. We also identified 42 haplotypes and 54 diplotypes of ADRB2 in a Japanese population. The frequencies were similar between the two groups. They were classified into 17 and 23 types, respectively, according to Drysdale's haplotype-organization system, and a significant ethnic difference was observed between the Japanese and Caucasian populations. CONCLUSIONS: The frequencies of SNPs and ADBR2 haplotypes in Japanese are different from those in Caucasians and African Americans. These divergences might imply the need for independent pharmacogenetic studies for ADBR2 in each ethnic group.

Helicobacter pylori infection influences expression of genes related to angiogenesis and invasion in human gastric carcinoma cells.

Infection with Helicobacter pylori (H. pylori) is considered a risk factor for gastric carcinoma. The purpose of this study was to clarify whether H. pylori infection plays a role in progression of gastric carcinoma. We examined the expression of genes encoding angiogenic factors and proteases by human gastric carcinoma cell lines (MKN-1 and TMK-1) co-cultured with or without H. pylori by cDNA microarray analysis. Co-culture with H. pylori increased expression of mRNAs encoding interleukin (IL)-8, vascular endothelial growth factor (VEGF), angiogenin, urokinase-type plasminogen activator (uPA), and metalloproteinase (MMP)-9 by gastric carcinoma cells. Up-regulation of these genes at the mRNA and protein levels was confirmed by Northern blot analysis, semi-quantitative RT-PCR analysis, and ELISA. In vitro angiogenic and collagenase activities of conditioned medium from the gastric carcinoma cells were also stimulated by co-culture with H. pylori. These results indicate that H. pylori infection may regulate angiogenesis and invasion of human gastric carcinoma.

Synergistic antiviral effect of a combination of mouse interferon-alpha and interferon-gamma on mouse hepatitis virus.

Although interferon (IFN)-alpha and IFN-gamma have been reported to exhibit a synergistic antiviral effect through the different signaling pathways in vitro, their therapeutic efficacy is not well defined in vivo. The current study was carried out to investigate the combined antiviral effect in a model of mouse hepatitis virus Type 2 (MHV-2) infection, in which fulminant hepatitis is developed. MHV-2 was injected intraperitoneally into 4-week-old ICR mice, IFN or the vehicle was administered intramuscularly for 5 days, and the antiviral effect was evaluated based on survival periods, liver histology, serum alanine transaminase (ALT) levels, and MHV-2 virus titers in the liver tissues. The animals in the group treated with a combination of IFN-alpha and IFN-gamma survived for longer periods than the groups treated with IFN-alpha alone and IFN-gamma alone (IFN-alpha 10(3) (IU/mouse)/-gamma 10(3) vs. IFN-alpha 10(3), P < 0.005; IFN-alpha 10(3)/-gamma 10(3) vs. IFN-gamma 10(3), P < 0.001). This is consistent with the lower levels of hepatocellular necrosis and serum ALT and the decreased titers of MHV-2 virus in the liver tissues (48 hr, P < 0.001; 72 hr, P < 0.001). These findings indicate that a combination of IFN-alpha and IFN-gamma exhibits a synergistic antiviral effect on MHV-2 infection. The biology of MHV-2 is quite different from that of human hepatitis viruses; however, these results suggest the beneficial combined therapy of IFN-alpha and IFN-gamma for the treatment of human viral hepatitis.