AIMIn order to discover new inhibitors and enhancers of nitric oxide synthase (NOS), an in vitro assay to determine NOS activity was established for high throughput screening.

METHODSThe activity of NOS was detected based on the change of nicotinamide-adenine dinucleotide phosphate (NADPH) concentration in the reaction system by the fluorescence density. The enzyme was prepared from bovine brain by gradient centrifugation. The reaction performed in black 96 well micro-plate with a final volume of 90 microL. Every factor which would affect the results such as the concentration of NADPH, L-arginine (L-Arg, used as substrate) and enzyme protein was optimized in different conditions. At last, 5,600 samples (compounds and extracts) were screened by the method.

RESULTSThe test signal (fluorescence density) in the reaction system was influenced by many different factors such as temperature and concentration of substrates. The ideal system contains protein 1.50 mg.mL-1, L-Arg 1 mmol.L-1, NADPH 0.1 mmol.L-1 at 37 degrees C. In this method, there were about 2% samples which emit fluorescence, and about 0.5% samples which quench the fluorescence. So these samples were deleted from the sample library. The effects of these samples on activity of NOS were distributed in a normal manner. About 2% samples had potential effects on the NOS activity (including inhibitors and enhancers).

CONCLUSIONThe method can be performed by high throughput screening and gives the stable data, not only for inhibitors, but also for enhancers of NOS activity.

Animals ; Arginine ; pharmacology ; Cattle ; Drug Evaluation, Preclinical ; methods ; Enzyme Inhibitors ; isolation & purification ; pharmacology ; In Vitro Techniques ; NADP ; pharmacology ; Nitric Oxide Synthase ; antagonists & inhibitors ; metabolism ; Nitroarginine ; pharmacology

Reactive oxygen species such as superoxides, hydrogen peroxide (H2O2) and hydroxyl radicals have been suggested to be involved in the catalytic action of nitric oxide synthase (NOS) to produce NO from L-arginine. An examination was conducted on the effects of oxygen radical scavengers and oxygen radical-generating systems on the activity of neuronal NOS and guanylate cyclase (GC) in rat brains and NOS from the activated murine macrophage cell line J774. Catalase and superoxide dismutase (SOD) showed no significant effects on NOS or GC activity. Nitroblue tetrazolium (NBT, known as a superoxide radical scavenger) and peroxidase (POD) inhibited NOS, but their inhibitory actions were removed by increasing the concentration of arginine or NADPH respectively, in the reaction mixture. NOS and NO-dependent GC were inactivated by ascorbate/FeSO4 (a metal-catalyzed oxidation system), 2'2'-azobis-amidinopropane (a peroxy radical producer), and xanthine/xanthine oxidase (a superoxide generating system). The effects of oxygen radicals or antioxidants on the two isoforms of NOS were almost similar. However, H2O2 activated GC in a dose-dependent manner from 100 microM to 1 mM without significant effects on NOS. H2O2-induced GC activation was blocked by catalase. These results suggested that oxygen radicals inhibited NOS and GC, but H2O2 could activate GC directly.
Animal ; Antioxidants/pharmacology ; Brain/enzymology ; Catalase/pharmacology ; Cell Line ; Guanylate Cyclase/metabolism* ; Hydrogen Peroxide/pharmacology ; Macrophages/enzymology ; NADP/pharmacology ; Nitric-Oxide Synthase/metabolism* ; Nitroblue Tetrazolium/pharmacology ; Rats ; Rats, Sprague-Dawley ; Reactive Oxygen Species/metabolism* ; Signal Transduction ; Superoxide Dismutase/pharmacology

OBJECTIVE: To explore the role of Runt-related transcription factor 3 (RUNX3) in metabolic regulation of trastuzumab-resistant gastric cancer cells and investigate the mechanism of RUNX3 knockdown-mediated reversal of trastuzumab resistance. METHODS: We performed a metabolomic analysis of trastuzumab-resistant gastric cancer cells (NCI N87R) and RUNX3 knockdown cells (NCI N87R/RUNX3) using ultra performance liquid chromatography (UPLC) coupled with Q Exactive Focus Orbitrap mass spectrometry (MS). Multivariate combined with univariate analyses and MS/MS ion spectrums were used to screen the differential variables. MetaboAnalyst 5.0 database was employed for pathway enrichment analysis. Differential metabolites-genes regulatory relationships were constructed based on OmicsNet database. The changes in GSH/GSSG and NADPH/NADP ratios in NCI N87R/RUNX3 cells were measured using detection kits. RESULTS: The metabolic profile of NCI N87R cells was significantly altered after RUNX3 knockdown, with 81 differential metabolites identified to contribute significantly to the classification, among which 43 metabolites were increased and 38 were decreased (P < 0.01). In NCI N87R cells, RUNX3 knockdown resulted in noticeable alterations in 8 pathways involving glutamine metabolism, glycolysis, glycerophospholipid, nicotinate-nicotinamide and glutathione metabolism, causing also significant reduction of intracellular GSH/GSSG and NADPH/NADP ratios (P < 0.01). The differential metabolites-genes network revealed a regulatory relationship between the metabolic molecules and genes. CONCLUSION RUNX3 reverses trastuzumab resistance in gastric cancer cells by regulating energy metabolism and oxidation-reduction homeostasis and may serve as a potential therapeutic target for trastuzumab-resistant gastric cancer.
Chromatography, High Pressure Liquid ; Core Binding Factor Alpha 3 Subunit/genetics* ; Glutathione Disulfide ; Humans ; Metabolomics ; NADP ; Stomach Neoplasms/genetics* ; Tandem Mass Spectrometry ; Trastuzumab/pharmacology*

The xylose reductase of Pichia stipitis is one of the most important enzymes. It can be used to build up recombinant Saccharomyces cerevisiae strain for utilizing xylose and producing ethanol. Intercellular redox imbalance caused by NADPH preference over NADH for Pichia stipitis xylose reductase (PsXR) has been considered to be one of the main factors for poor ethanol productivity. Some key amino acids of PsXR, which affect the activity or coenzyme preference, were investigated in our previous study. In this study, Lys21 were rational designed for site-directed mutagenesis to alter coenzyme specificity of PsXR from NADPH and NADH into single NADH. The wild gene and mutagenesis genes were ligated into pET28b, and were transferred into E.coli BL21(DE3). After induced by IPTG, the xylose reductases were purified. Purified mutants K21A (Lys21-->Ala), K21R(Lys21-->Arg) were characterized by steady-state kinetic analysis. The results showed that the coenzyme dependence of K21A was completely reversed to NADH.
Aldehyde Reductase ; metabolism ; Amino Acid Substitution ; genetics ; Coenzymes ; pharmacology ; Escherichia coli ; genetics ; metabolism ; Ethanol ; pharmacology ; Lysine ; genetics ; Mutagenesis, Site-Directed ; NAD ; metabolism ; NADP ; metabolism ; Pichia ; chemistry ; genetics ; metabolism ; Recombinant Proteins ; biosynthesis ; genetics ; metabolism ; Recombination, Genetic ; Xylose ; pharmacology

OBJECTIVETo study the effect of Jianpi Liqi Recipe (JLR) on 5-fluorouracil (5-FU) relevant metabolic enzymes and CYP3A4 (the same enzyme of many chemotherapeutics) of mice with human gastric cancer transplanted tumor.

METHODSTotally 80 mice were randomly divided into the model group, the chemotherapy group, the JLR group, and the combination group (using chemotherapy combined JLR), 20 in each group. The human gastric cancer transplanted tumor mouse model was duplicated by hypodermic inoculating MKN-8 tumor cell suspension from the left armpit. Physiological saline or JLR was given to those in the model group or the JLR group at 0.25 mL each time, twice daily by gastrogavage from the 2nd day after transplantation. Mice in the chemotherapy group were given 0.25 mL physiological saline, twice daily by gastrogavage 2 days after transplantation, for 5 days in succession, and then they were peritoneal injected with 5-FU at the daily dose of 20 mg/kg, once daily for 5 days in succession from the 7th day of transplantation. Those in the combination were given 0.25 mL JLR, twice daily by gastrogavage, for 5 days in succession, and then they were peritoneal injected with 5-FU at the daily dose of 20 mg/kg, once daily for 5 days in succession from the 7th day of transplantation. The mRNA expressions of thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD), and CYP3A4 were detected using RT-PCR.

RESULTSCompared with the model group and the chemotherapy group, mRNA expressions of TP and CYP3A4 obviously increased, mRNA expression of DPD obviously decreased in the JLR group and the combination group (P < 0.01). There was no statistical difference in mRNA expressions of TP, DPD, and CYP3A4 between the JLR group and the combination group (P > 0.05).

CONCLUSIONJLR could promote the activation of 5-FU, suppress the decomposition and inactivation of 5-FU in the tumor tissue of mice, and improve the chemotherapeutic efficacy through up-regulating mRNA expressions of TP and CYP3A4, and suppressing the mRNA expression of DPD.

Animals ; Cytochrome P-450 CYP3A ; genetics ; Dihydrouracil Dehydrogenase (NADP) ; genetics ; Drugs, Chinese Herbal ; pharmacology ; Gene Expression Regulation, Neoplastic ; Humans ; Male ; Mice ; Mice, Inbred Strains ; RNA, Messenger ; genetics ; Stomach Neoplasms ; enzymology ; genetics ; Thymidine Phosphorylase ; genetics ; Xenograft Model Antitumor Assays

The metabolic characteristics of ligustrazin (TMPz) in liver microsomes were investigated in the present study. The reaction phenotyping of TMPz metabolism was also identified by in vitro assessment using recombinant human cytochrome P450 enzymes (CYP) and UDP glucuronosyltransferases (UGT). TMPz was incubated at 37 degrees C with human (HLM) and rat liver microsomes (RLM) in the presence of different co-factors. The metabolic stability and enzyme kinetics of TMPz were studied by determining its remaining concentrations with a LC-MS/MS method. TMPz was only metabolically eliminated in the microsomes with NADPH or NADPH+UDPGA. In the HLM and RLM with NADPH+UDPGA, t1/2, K(m) and V(max) of TMPz were 94.24 +/- 4.53 and 105.07 +/- 9.44 min, 22.74 +/- 1.89 and 33.09 +/- 2.74 micromol x L(-1), 253.50 +/- 10.06 and 190.40 +/- 8.35 nmol x min(-1) x mg(-1) (protein), respectively. TMPz showed a slightly higher metabolic rate in HLM than that in RLM. Its primary oxidative metabolites, 2-hydroxymethyl-3, 5, 6-trimethylpyrazine (HTMP), could undergo glucuronide conjugation. The CYP reaction phenotyping of TMPz metabolism was identified using a panel of recombinant CYP isoforms (rCYP) and specific CYP inhibitors in HLM. CYP1A2, 2C9 and 3A4 were found to be the major CYP isoforms involved in TMPz metabolism. Their individual contributions were assessed b) using the method of the total normalized rate to be 19.32%, 27.79% and 52.90%, respectively. It was observed that these CYP isoforms mediated the formation of HTMP in rCYP incubation. The UGT reaction phenotyping of HTMP glucuronidation was also investigated preliminarily by using a panel of 6 UGT isoforms (rUGT). UGT1A1, 1A4 and 1A6 were the predominant isoforms mediated the HTMP glucuronidation. The results above indicate that the metabolism of TMPz involves multiple enzymes mediated phase I and phase II reactions.
Animals ; Cytochrome P-450 CYP1A2 ; metabolism ; Cytochrome P-450 CYP2C9 ; metabolism ; Cytochrome P-450 CYP3A ; metabolism ; Cytochrome P-450 Enzyme Inhibitors ; Cytochrome P-450 Enzyme System ; metabolism ; Drug Interactions ; Glucuronosyltransferase ; metabolism ; Humans ; Ligusticum ; chemistry ; Microsomes, Liver ; enzymology ; NADP ; metabolism ; pharmacology ; Pyrazines ; metabolism ; pharmacokinetics ; Rats ; Uridine Diphosphate Glucuronic Acid ; metabolism ; pharmacology