Oxidoreductases, N-Demethylating

Publication Title: 
Proceedings of the National Academy of Sciences of the United States of America

Transcriptional dysregulation is an early feature of Huntington disease (HD). We observed gene-specific changes in histone H3 lysine 4 trimethylation (H3K4me3) at transcriptionally repressed promoters in R6/2 mouse and human HD brain. Genome-wide analysis showed a chromatin signature for this mark. Reducing the levels of the H3K4 demethylase SMCX/Jarid1c in primary neurons reversed down-regulation of key neuronal genes caused by mutant Huntingtin expression. Finally, reduction of SMCX/Jarid1c in primary neurons from BACHD mice or the single Jarid1 in a Drosophila HD model was protective.

Author(s): 
Vashishtha, Malini
Ng, Christopher W.
Yildirim, Ferah
Gipson, Theresa A.
Kratter, Ian H.
Bodai, Laszlo
Song, Wan
Lau, Alice
Labadorf, Adam
Vogel-Ciernia, Annie
Troncosco, Juan
Ross, Christopher A.
Bates, Gillian P.
Krainc, Dimitri
Sadri-Vakili, Ghazaleh
Finkbeiner, Steven
Marsh, J. Lawrence
Housman, David E.
Fraenkel, Ernest
Thompson, Leslie M.
Publication Title: 
Molecular Cell

Histone H3K4 demethylase LSD1 plays an important role in stem cell biology, especially in the maintenance of the silencing of differentiation genes. However, how the function of LSD1 is regulated and the differentiation genes are derepressed are not understood. Here, we report that elimination of LSD1 promotes embryonic stem cell (ESC) differentiation toward neural lineage. We showed that the destabilization of LSD1 occurs posttranscriptionally via the ubiquitin-proteasome pathway by an E3 ubiquitin ligase, Jade-2.

Author(s): 
Han, Xiao
Gui, Bin
Xiong, Cong
Zhao, Linnan
Liang, Jing
Sun, Luyang
Yang, Xiaohan
Yu, Wenhua
Si, Wenzhe
Yan, Ruorong
Yi, Xia
Zhang, Di
Li, Wanjin
Li, Lifang
Yang, Jianguo
Wang, Yan
Sun, Yi Eve
Zhang, Dai
Meng, Anming
Shang, Yongfeng
Publication Title: 
Drug and Alcohol Dependence

Induction of hepatic propoxyphene N-demethylase and aniline hydroxylase activities resulted following repeated oral administration of 25, 50 and 100 mg d-propoxyphene hydrochloride per kg daily in the mouse over a six-day period. A significant elevation in both enzyme activities was noted after a single dose of propoxyphene (100 mg/kg). A dose-related response characterized the observed induction of each microsomal enzyme activity.

Author(s): 
Masten, L. W.
Publication Title: 
British Journal of Clinical Pharmacology

AIMS: The study aimed to identify the specific human cytochrome P450 (CYP450) enzymes involved in the metabolism of artemisinin. METHODS: Microsomes from human B-lymphoblastoid cell lines transformed with individual CYP450 cDNAs were investigated for their capacity to metabolize artemisinin. The effect on artemisinin metabolism in human liver microsomes by chemical inhibitors selective for individual forms of CYP450 was investigated.

Author(s): 
Svensson, U. S.
Ashton, M.
Publication Title: 
European Journal of Clinical Pharmacology

OBJECTIVE: Cytochrome P450 2B6 (CYP2B6) is involved in the metabolism of artemisinin drugs, a novel series of antimalarials. Our aim was to analyze the prevalence of the most commonly observed CYP2B6 alleles in malaria-endemic populations of West Africa (WA) and Papua New Guinea (PNG). METHODS: Using a post-PCR ligation detection reaction-fluorescent microsphere assay, frequencies of CYP2B6*1A, *2, *3, *4, *5, *6, *7, and *9 were determined in WA (n=166) and PNG (n=174).

Author(s): 
Mehlotra, Rajeev K.
Ziats, Mark N.
Bockarie, Moses J.
Zimmerman, Peter A.
Publication Title: 
Drug Metabolism and Disposition: The Biological Fate of Chemicals

Artemether (AM) is one of the most effective antimalarial drugs. The elimination half-life of AM is very short, and it shows large interindividual variability in pharmacokinetic parameters. The aim of this study was to identify cytochrome P450 (P450) isozymes responsible for the demethylation of AM and to evaluate functional differences between 26 CYP2B6 allelic variants in vitro. Of 14 recombinant P450s examined in this study, CYP2B6 and CYP3A4 were primarily responsible for production of the desmethyl metabolite dihydroartemisinin.

Author(s): 
Honda, Masashi
Muroi, Yuka
Tamaki, Yuichiro
Saigusa, Daisuke
Suzuki, Naoto
Tomioka, Yoshihisa
Matsubara, Yoichi
Oda, Akifumi
Hirasawa, Noriyasu
Hiratsuka, Masahiro
Publication Title: 
Drug Metabolism and Disposition: The Biological Fate of Chemicals

Artemisinin drugs have become the first-line antimalarials in areas of multidrug resistance. However, monotherapy with artemisinin drugs results in comparatively high recrudescence rates. Autoinduction of cytochrome P450 (P450)-mediated metabolism, resulting in reduced exposure, has been supposed to be the underlying mechanism.

Author(s): 
Xing, Jie
Kirby, Brian J.
Whittington, Dale
Wan, Yakun
Goodlett, David R.
Publication Title: 
Carcinogenesis

The effects of ethanol on the metabolism of nitrosamines by rat liver microsomes have been studied. Treatment of rats with 10 or 15% ethanol in drinking water for 3 days causes a 4- to 5-fold enhancement in microsomal N-nitrosodimethylamine demethylase (NDMAd) activity and a 40-60% increase in gross P-450 content. The enhancement is mainly due to the induction of a low Km form (Km = 0.07 mM) of NDMAd. The treatment induces protein species with molecular weights between 50000 and 52000, some of which are believed to be P-450 isozymes with high affinity to NDMA.

Author(s): 
Peng, R.
Tu, Y. Y.
Yang, C. S.
Publication Title: 
Cancer Research

In order to elucidate the enzymic basis of nitrosamine metabolism, the in vitro metabolism of nitrosamines by rat liver microsomes and the effects of fasting on the microsomal enzymes have been studied. Fasting for 1 to 3 days causes a 2- to 3-fold enhancement of the reduced nicotinamide adenine dinucleotide phosphate-dependent nitrosodimethylamine demethylase (NDMAD) activity. The cytochrome P-450 content and the activities of reduced nicotinamide adenine dinucleotide phosphate-cytochrome P-450 reductase and benzphetamine demethylase, however, are only modestly increased.

Author(s): 
Tu, Y. Y.
Yang, C. S.
Publication Title: 
Chemico-Biological Interactions

The effects of acetone and isopropanol on the microsomal monooxygenase system have been investigated to study the role of this enzyme system in the metabolism of nitrosamines. Treatment of rats with acetone or isopropanol (2.5-5 ml/kg, i.g.) causes a 3-4.5-fold enhancement in the NADPH-dependent nitrosodimethylamine demethylase (NDMAd) activity. This is accompanied by only moderate increases in the gross cytochrome P-450 (P-450) content and NADPH-cytochrome c reductase activity.

Author(s): 
Tu, Y. Y.
Peng, R.
Chang, Z. F.
Yang, C. S.

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