Congenital methemoglobinemia is caused by NADH-methemoglobin reductase deficiency in more than half of the total reported cases. NADH-methemoglobin reductase deficiency is an uncommon hereditary disorder producing methemoglobinemia and cyanosis in the homozygous subject. A majority of the patients born with these abnormalities have only a cosmetic defect-asymptomatic cyanosis. Congenital methemoglobinemia due to NADH-methemoglobin reductase deficiency is an autosomal recessive disorder and classified into 4 types according to the pathophysiology of the disorder. In type I, the deficiency of NADH-methemoglobin reductase is restricted to erythrocytes of patients with mild cyanosis, and 7 missence mutations have been reported in the case of type I. We report the first Korean pediatric case of type I congenital methemoglobinemia due to NADH- methemoglobin reductase deficiency with a review of the literature.
Cyanosis ; Cytochrome-B(5) Reductase ; Erythrocytes ; Humans ; Methemoglobinemia* ; Oxidoreductases*

The activity of NADH-cytochrome b(5) reductase (b(5)R) and the levels of hydrogen peroxide in the thyroid of patients with Graves' disease (GD) and normal controls were measured with potassium ferricyanide as substrate and with the homovanillic acid fluorescence assay. The activity of b(5)R and the level of H2O2 in GD thyroid were definitely higher than those in normal control, but the activity of catalase in GD thyroid was not significantly different from that in normal thyroid. After addition of p-chloromercuribenzoate, a b(5)R inhibitor, the activity of b(5)R in GD and normal thyroid decreased by 85%, the level of H2O2 decreased by 50%, and protein-bound iodine (PBI) formation by 52%. There is a positive correlation between the level of H2O2 and the activity of b(5)R. Our data indicate that b(5)R participates in thyroid hydrogen peroxide biosynthesis, and is an important enzyme in the production of H2O2.
Case-Control Studies ; Cytochrome-B(5) Reductase ; metabolism ; Graves Disease ; metabolism ; Humans ; Hydrogen Peroxide ; metabolism ; Thyroid Gland ; enzymology

<b>BACKGROUNDb>Cytochrome b5 reductase 2 (CYB5R2) is a potential tumor suppressor that inhibits cell proliferation and motility in nasopharyngeal carcinoma (NPC). Inactivation of CYB5R2 is associated with lymph node metastasis in NPC. This study aimed to explore the mechanisms contributing to the anti-neoplastic effects of CYB5R2.

<b>METHODSb>Polymerase chain reaction (PCR) assays were used to analyze the transcription of 84 genes known to be involved in representative cancer pathways in the NPC cell line HONE1. NPC cell lines CNE2 and HONE1 were transiently transfected with CYB5R2, and data was validated by real-time PCR. A chick chorioallantoic membrane (CAM) embryo model was implanted with CYB5R2-expressing CNE2 and HONE1 cells to evaluate the effect of CYB5R2 on angiogenesis. An immunohistochemical assay of the CAM model was used to analyze the protein expression of vascular endothelial growth factor (VEGF).

<b>RESULTSb>In CYB5R2-transfected NPC cells, PCR assays revealed up-regulated mRNA levels of Fas cell surface death receptor (FAS), FBJ murine osteosarcoma viral oncogene homolog (FOS), phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1), integrin beta 3 (ITGB3), metastasis suppressor 1 (MTSS1), interferon beta 1 (IFNB1), and cyclin-dependent kinase inhibitor 2A (CDKN2A) and down-regulated levels of integrin beta 5 (ITGB5), insulin-like growth factor 1 (IGF1), TEK tyrosine kinase (TEK), transforming growth factor beta receptor 1 (TGFBR1), and VEGF. The angiogenesis in the CAM model implanted with CYB5R2-transfected NPC cells was inhibited. Down-regulation of VEGF by CYB5R2 in NPC cells was confirmed by immunohistochemical staining in the CAM model.

<b>CONCLUSIONb>CYB5R2 up-regulates the expression of genes that negatively modulate angiogenesis in NPC cells and down-regulates the expression of VEGF to reduce angiogenesis, thereby suppressing tumor formation.

Animals ; Carcinoma ; Cell Line, Tumor ; Cell Movement ; Cell Proliferation ; Chickens ; Cytochrome-B(5) Reductase ; Down-Regulation ; Gene Regulatory Networks ; Genes, Tumor Suppressor ; Humans ; Nasopharyngeal Neoplasms ; Neovascularization, Pathologic ; Oxidoreductases ; Real-Time Polymerase Chain Reaction ; Transfection ; Up-Regulation ; Vascular Endothelial Growth Factor A

<b>OBJECTIVEb>To establish a cell line with human NADH-cytochrome b5 reductase (b5R) deficiency via RNA interference (RNAi).

<b>METHODSb>Two siRNA expressing vectors targeting the b5R mRNA were designed and constructed. Hepatocellular carcinoma BEL-7402 cells were transiently transfected with the two recombinants by lipofectamine (TM) 2000, and semi-quantitative RT-PCR was carried out to analyze the suppression of b5R mRNA; BEL-7402 cells stably transfected with the two siRNA expressing vectors were selected in the media with G418. By analyses of the mRNA, enzymatic activity and protein level of b5R, several cell clones with deficiency of b5R were established. The cell growth curve of BEL-7402 cells with b5R deficiency was detected by MTT assay.

<b>RESULTSb>Two siRNA expressing vectors targeting b5R mRNA were obtained, namely pSib5R-1 and pSib5R-2. When BEL-7402 cells were transfected transiently with pSib5R-2, the expression of b5R mRNA was significantly suppressed with a suppression ratio of 68.3%, indicating that pSib5R-2 could trigger the degradation of b5R mRNA effectively. Eighteen clones stably integrated exogenous plasmids were obtained. In two clones from pSib5R-2 transfection, the expression of b5R mRNA was suppressed by up to 48.2% and 56.2%, and the enzymatic activity was inhibited by up to 54.6% and 63.5%, respectively. The protein levels also decreased significantly. The defect of b5R did not change the cell growth rate.

<b>CONCLUSIONb>The expression of b5R in BEL-7402 could be suppressed by vector-based RNA interference effectively. We established a cellular model with defect of b5R successfully, which can be used as a tool in investigation of the biological function of b5R and molecular mechanism of type II recessive congenital methemoglobinemia.

Cell Culture Techniques ; Cell Line, Tumor ; enzymology ; Cells ; enzymology ; Cytochrome-B(5) Reductase ; deficiency ; genetics ; Gene Expression ; drug effects ; Genetic Vectors ; Humans ; RNA Interference ; physiology ; RNA, Messenger ; metabolism ; RNA, Small Interfering ; pharmacology ; Transfection

This paper is aimed to study the metabolic kinetics of nicousamide in rat liver microsomes and cytosol and to identify the major metabolite and drug metabolizing enzymes involved in the metabolism of nicousamide in rat and human liver microsomes by selective inhibitors in vitro. The concentration of nicousamide was determined by HPLC-UV method. The metabolite of nicousamide in rat and human liver microsomes was isolated and identified by LC-MS/MS. The major metabolite of nicousamide in rat and human liver microsomes was identified to be 3-(3'-carboxy-4'-hydroxy-anilino-carbo-)-6-amino-7-hydroxy-8-methyl-coumarin (M1). The metabolite of nicousamide in rat plasma, urine, bile and liver was consistent with M1. The metabolism of nicousamide can be catalyzed by several reductases, including CYP450 reductases, cytochrome b5 reductases and CYP2C6 in rat liver microsomes, as well as xanthine oxidase and DT-diaphorase in rat liver cytosol.
Adenosine Monophosphate ; pharmacology ; Allopurinol ; pharmacology ; Aniline Compounds ; metabolism ; Animals ; Cimetidine ; pharmacology ; Coumarins ; metabolism ; Cytochrome P-450 Enzyme Inhibitors ; Cytochrome P450 Family 2 ; Cytochrome-B(5) Reductase ; antagonists & inhibitors ; Cytosol ; metabolism ; Dicumarol ; pharmacology ; Enzyme Inhibitors ; pharmacology ; Female ; Humans ; Liver ; cytology ; metabolism ; Male ; Microsomes, Liver ; metabolism ; Mitochondria, Liver ; metabolism ; NAD(P)H Dehydrogenase (Quinone) ; antagonists & inhibitors ; Propylthiouracil ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Steroid 21-Hydroxylase ; antagonists & inhibitors ; Xanthine Oxidase ; antagonists & inhibitors