ABSTRACT
To provide the profiles of metabolism of mitomycin C (MMC) by human liver microsomes in vitro, MMC was incubated with human liver microsomes, then the supernatant component was isolated and detected by HPLC. Types of metabolic enzymes were estimated by the effect of NADPH or dicumarol (DIC) on metabolism of MMC. Standard, reaction, background control (microsomes was inactivated), negative control (no NADPH), and inhibitor group (adding DIC) were assigned, the results were analyzed by Graphpad Prism 4. 0 software. Reaction group compared with background control and negative control groups, 3 NADPH-dependent absorption peaks were additionally isolated by HPLC after MMC were incubated with human liver microsomes. Their retention times were 10. 0, 14. 0, 14. 8 min ( named as Ml, M2, M3) , respectively. Their formation was kept as Sigmoidal dose-response and their Km were 0. 52 (95% CI, 0. 40 - 0.67) mmol x L(-1), 0. 81 (95% CI, 0. 59 - 1. 10) mmol x L(-1), 0. 54 (95% CI, 0. 41 -0. 71) mmol x L(-1) , respectively. The data indicated that the three absorption peaks isolated by HPLC were metabolites of MMC. DIC can inhibit formation of M2, it' s dose-effect fitted to Sigmoidal curve and it' s IC50 was 59. 68 (95% CI, 40. 66 - 87. 61) micromol x L(-1) , which indicated DT-diaphorase could take part in the formation of M2. MMC can be metabolized by human liver microsomes in vitro, and at least three metabolites of MMC could be isolated by HPLC in the experiment, further study showed DT-diaphorase participated in the formation of M2.
Subject(s)
Humans , Antibiotics, Antineoplastic , Metabolism , Chromatography, High Pressure Liquid , Methods , Dicumarol , Pharmacology , Dose-Response Relationship, Drug , Enzyme Inhibitors , Pharmacology , Microsomes, Liver , Metabolism , Mitomycin , MetabolismABSTRACT
This study is to evaluate the cytotoxicity of mitomycin C (MMC) and its analogue 5-(aziridin-1-yl)-3-hydroxymethyl-1-methylindole-4,7-dione (629) as well as the effect of transfection of constitutive androstane receptor (CAR) on their biological effects. HepG2 cells were transfected with the plasmids mCAR1/pCR3 mediated by liposome. Vector pCR3 was used as control. Transfected cells were screened by G418 resistance and limiting dilution. The expressions of plasmid mCAR1/pCR3 and CYP2B6 mRNA were detected by RT-PCR; Cytotoxicities of MMC and 629 in vitro were evaluated in g2car cells and HepG2 cells by MTT method under anaerobic and aerobic conditions. mRNA expression of CAR and CYP2B6 can not be detected in HepG2 cells and HepG2/pCR3 cells but can in g2car cells. It is shown that plasmid mCAR1/pCR3 was transfected into g2car cells successfully and target CYP2B6 was transactivated by CAR. To compare with aerobic and anaerobic, the cytotoxicities of MMC and 629 to HepG2 cells and g2car cells had significantly enhanced (P < 0.05), and transfect CAR gene can improve the cytotoxicity of MMC (P < 0.05), but not 629 (P > 0.05). Furthermore, CYP2B6 is one master enzyme for the metabolism of MMC and not 629. Transfection of CAR can increase expression of CYP2B6 mRNA in HepG2 cells, and can affect cytotoxicities of MMC and 629.
Subject(s)
Humans , Antibiotics, Antineoplastic , Pharmacology , Aryl Hydrocarbon Hydroxylases , Genetics , Aziridines , Pharmacology , Carcinoma, Hepatocellular , Metabolism , Pathology , Cell Death , Cell Hypoxia , Cell Line, Tumor , Cytochrome P-450 CYP2B6 , Indoles , Pharmacology , Inhibitory Concentration 50 , Liver Neoplasms , Metabolism , Pathology , Mitomycin , Pharmacology , Oxidoreductases, N-Demethylating , Genetics , Plasmids , RNA, Messenger , Metabolism , Receptors, Cytoplasmic and Nuclear , Genetics , Recombinant Proteins , Genetics , Transcription Factors , Genetics , TransfectionABSTRACT
<p><b>AIM</b>To examine the effect of inducible nitric oxide synthase (iNOS) on tumour cells chemosensitivity to mitomycin C (MMC) analogue 5-aziridinyl-3-hydroxyl-1-methylindole-4,7-dione (629) in vitro, and elucidate the possible role of iNOS in the metabolism of 629.</p><p><b>METHODS</b>Human sarcoma cells (HT1080) and its iNOS gene transfected clones (iNOS9, iNOS12) were exposed to 629 at concentrations of 1 nmol x L(-1) - 100 micromol x L(-1). 3-[4, 5-Dimethylthiazol-2-yl] -2,5-diphenyltetrazolium bromide (MTT) assay, agarose electrophoresis and flow cytometric analysis were used to determine cell sensitivity, deoxyribonucleic acid (DNA) damage and the change of cell cycle in above process, respectively. All experiments were performed both in air and under hypoxia parallelly.</p><p><b>RESULTS</b>629 was more toxic than MMC, and enhanced cytotoxicity under hypoxia, which resulted in cell necrosis. Sixteen hours after treated with 629, HT1080 cells and related iNOS-transfected clone cells were obviously blocked in G2/M phase.</p><p><b>CONCLUSION</b>iNOS plays dual roles in 629 metabolism, enhancing or decreasing the cytoxicity of 629 depending on the intracellular oxygen pressure P(O2), which caused higher cytotoxicity to hypoxia cells of 629 with the increasing of iNOS activity.</p>