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  1. Article: MicroRNA-483-5p Inhibits Hepatocellular Carcinoma Cell Proliferation, Cell Steatosis, and Fibrosis by Targeting PPARα and TIMP2.

    Niture, Suryakant / Gadi, Sashi / Qi, Qi / Gyamfi, Maxwell Afari / Varghese, Rency S / Rios-Colon, Leslimar / Chimeh, Uchechukwu / Vandana / Ressom, Habtom W / Kumar, Deepak

    Cancers

    2023  Volume 15, Issue 6

    Abstract: MicroRNAs (miRNAs) are small non-coding RNA molecules that bind with the 3' untranslated regions (UTRs) of genes to regulate expression. Downregulation of miR-483-5p (miR-483) is associated with the progression of hepatocellular carcinoma (HCC). However, ...

    Abstract MicroRNAs (miRNAs) are small non-coding RNA molecules that bind with the 3' untranslated regions (UTRs) of genes to regulate expression. Downregulation of miR-483-5p (miR-483) is associated with the progression of hepatocellular carcinoma (HCC). However, the significant roles of miR-483 in nonalcoholic fatty liver disease (NAFLD), alcoholic fatty liver diseases (AFLD), and HCC remain elusive. In the current study, we investigated the biological significance of miR-483 in NAFLD, AFLD, and HCC in vitro and in vivo. The downregulation of miR-483 expression in HCC patients' tumor samples was associated with Notch 3 upregulation. Overexpression of miR-483 in a human bipotent progenitor liver cell line HepaRG and HCC cells dysregulated Notch signaling, inhibited cell proliferation/migration, induced apoptosis, and increased sensitivity towards antineoplastic agents sorafenib/regorafenib. Interestingly, the inactivation of miR-483 upregulated cell steatosis and fibrosis signaling by modulation of lipogenic and fibrosis gene expression. Mechanistically, miR-483 targets PPARα and TIMP2 gene expression, which leads to the suppression of cell steatosis and fibrosis. The downregulation of miR-483 was observed in mice liver fed with a high-fat diet (HFD) or a standard Lieber-Decarli liquid diet containing 5% alcohol, leading to increased hepatic steatosis/fibrosis. Our data suggest that miR-483 inhibits cell steatosis and fibrogenic signaling and functions as a tumor suppressor in HCC. Therefore, miR-483 may be a novel therapeutic target for NAFLD/AFLD/HCC management in patients with fatty liver diseases and HCC.
    Language English
    Publishing date 2023-03-10
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2527080-1
    ISSN 2072-6694
    ISSN 2072-6694
    DOI 10.3390/cancers15061715
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Pathogenesis of alcoholic liver disease: the role of nuclear receptors.

    Gyamfi, Maxwell Afari / Wan, Yu-Jui Yvonne

    Experimental biology and medicine (Maywood, N.J.)

    2010  Volume 235, Issue 5, Page(s) 547–560

    Abstract: Ethanol consumption causes fatty liver, which can lead to inflammation, fibrosis, cirrhosis and even liver cancer. The molecular mechanisms by which ethanol exerts its damaging effects are extensively studied, but not fully understood. It is now evident ... ...

    Abstract Ethanol consumption causes fatty liver, which can lead to inflammation, fibrosis, cirrhosis and even liver cancer. The molecular mechanisms by which ethanol exerts its damaging effects are extensively studied, but not fully understood. It is now evident that nuclear receptors (NRs), including retinoid x receptor alpha and peroxisome proliferator-activated receptors, play key roles in the regulation of lipid homeostasis and inflammation during the pathogenesis of alcoholic liver disease (ALD). Given their pivotal roles in physiological processes, NRs represent potential therapeutic targets for the treatment and prevention of numerous metabolic and lipid-related diseases including ALD. This review summarizes the factors that contribute to ALD and the molecular mechanisms of ALD with a focus on the role of NRs.
    MeSH term(s) Animals ; Disease Models, Animal ; Endocrine System/metabolism ; Ethanol/metabolism ; Humans ; Inflammation/complications ; Inflammation/pathology ; Liver Diseases, Alcoholic/complications ; Liver Diseases, Alcoholic/etiology ; Liver Diseases, Alcoholic/metabolism ; Liver Diseases, Alcoholic/pathology ; Receptors, Cytoplasmic and Nuclear/metabolism
    Chemical Substances Receptors, Cytoplasmic and Nuclear ; Ethanol (3K9958V90M)
    Language English
    Publishing date 2010-05-12
    Publishing country England
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Review
    ZDB-ID 4015-0
    ISSN 1535-3699 ; 1525-1373 ; 0037-9727
    ISSN (online) 1535-3699 ; 1525-1373
    ISSN 0037-9727
    DOI 10.1258/ebm.2009.009249
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: Mechanisms of resistance of hepatocyte retinoid X receptor alpha-null mice to WY-14,643-induced hepatocyte proliferation and cholestasis.

    Gyamfi, Maxwell Afari / Wan, Yu-Jui Yvonne

    The Journal of biological chemistry

    2009  Volume 284, Issue 14, Page(s) 9321–9330

    Abstract: Peroxisome proliferators, such as the lipid-lowering fibrates that function as agonists for peroxisome proliferator-activated receptor alpha (PPARalpha), induce liver tumors in rodents and may produce cholestasis in humans. Considerable attention has ... ...

    Abstract Peroxisome proliferators, such as the lipid-lowering fibrates that function as agonists for peroxisome proliferator-activated receptor alpha (PPARalpha), induce liver tumors in rodents and may produce cholestasis in humans. Considerable attention has focused on peroxisome proliferator-induced hepatocellular carcinoma, a phenomenon not noted in man, whereas limited studies examine fibrates and other therapeutic drugs that induce cholestasis, a common finding in humans. Moreover, the mechanisms by which fibrates induce hepatocyte proliferation and cholestasis are still not fully understood. We have examined the role of hepatocyte retinoid X receptor alpha (RXRalpha), an essential partner of PPARalpha, in modulating WY-14,643-induced hepatocyte proliferation and cholestasis. WY-14,643 treatment induced hepatomegaly in wild type (WT) mice that was also accompanied by induction of the expression of cyclins D1, D3, A2, and B1 and Cdc2 as well as inhibition of Wee 1. Such changes were either absent or greatly reduced in hepatocyte RXRalpha-null mice. Furthermore, neither WY-14,643 treatment nor RXRalpha deficiency affected apoptosis, indicating the importance of PPARalpha/RXRalpha in regulating Wee 1-mediated Cdc2/cyclin B1 expression for cells to enter into mitosis. WY-14,643 treatment also induced cholestasis and liver injury, which is evidenced by induction of alanine aminotransferase, alkaline phosphatase, and hepatic bile acid levels in WT mice. Hepatocyte RXRalpha deficiency protected the mice from WY-14,643-induced liver injury. WY-14,643-mediated induction of the small heterodimer partner, Mrp3, and Cyp3a11 levels was greater in hepatocyte RXRalpha-null than in WT mouse livers suggesting enhanced repression of bile acid synthesis and increased efflux of bile acids into blood for renal excretion as well as hydroxylation of bile acids because of hepatocyte RXRalpha deficiency. These data establish a crucial role of hepatocyte RXRalpha in regulating WY-14,643-mediated cell cycle progression as well as bile acid homeostasis.
    MeSH term(s) Animals ; Bile Acids and Salts/metabolism ; Cell Proliferation/drug effects ; Cholestasis/genetics ; Cholestasis/metabolism ; Cholestasis/pathology ; Cholesterol 7-alpha-Hydroxylase/metabolism ; Cytokines/genetics ; Cytokines/metabolism ; Gene Expression Regulation/drug effects ; Hepatocytes/cytology ; Hepatocytes/drug effects ; Hepatocytes/metabolism ; Hepatomegaly/chemically induced ; Hepatomegaly/pathology ; Mice ; Mice, Knockout ; Peroxisomes/metabolism ; Pyrimidines/pharmacology ; RNA, Messenger/genetics ; Receptors, Cytoplasmic and Nuclear/metabolism ; Retinoid X Receptor alpha/deficiency ; Retinoid X Receptor alpha/genetics ; Retinoid X Receptor alpha/metabolism ; Steroid 12-alpha-Hydroxylase/metabolism
    Chemical Substances Bile Acids and Salts ; Cytokines ; Pyrimidines ; RNA, Messenger ; Receptors, Cytoplasmic and Nuclear ; Retinoid X Receptor alpha ; nuclear receptor subfamily 0, group B, member 2 ; pirinixic acid (86C4MRT55A) ; Cholesterol 7-alpha-Hydroxylase (EC 1.14.14.23) ; Cyp7a1 protein, mouse (EC 1.14.14.23) ; Steroid 12-alpha-Hydroxylase (EC 1.14.18.8)
    Language English
    Publishing date 2009-01-27
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 2997-x
    ISSN 1083-351X ; 0021-9258
    ISSN (online) 1083-351X
    ISSN 0021-9258
    DOI 10.1074/jbc.M808861200
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Mechanisms of Resistance of Hepatocyte Retinoid X Receptor α-Null Mice to WY-14,643-induced Hepatocyte Proliferation and Cholestasis

    Gyamfi, Maxwell Afari / Wan, Yu-Jui Yvonne

    Journal of biological chemistry. 2009 Apr. 3, v. 284, no. 14

    2009  

    Abstract: Peroxisome proliferators, such as the lipid-lowering fibrates that function as agonists for peroxisome proliferator-activated receptor α (PPARα), induce liver tumors in rodents and may produce cholestasis in humans. Considerable attention has focused on ... ...

    Abstract Peroxisome proliferators, such as the lipid-lowering fibrates that function as agonists for peroxisome proliferator-activated receptor α (PPARα), induce liver tumors in rodents and may produce cholestasis in humans. Considerable attention has focused on peroxisome proliferator-induced hepatocellular carcinoma, a phenomenon not noted in man, whereas limited studies examine fibrates and other therapeutic drugs that induce cholestasis, a common finding in humans. Moreover, the mechanisms by which fibrates induce hepatocyte proliferation and cholestasis are still not fully understood. We have examined the role of hepatocyte retinoid X receptor α (RXRα), an essential partner of PPARα, in modulating WY-14,643-induced hepatocyte proliferation and cholestasis. WY-14,643 treatment induced hepatomegaly in wild type (WT) mice that was also accompanied by induction of the expression of cyclins D1, D3, A2, and B1 and Cdc2 as well as inhibition of Wee 1. Such changes were either absent or greatly reduced in hepatocyte RXRα-null mice. Furthermore, neither WY-14,643 treatment nor RXRα deficiency affected apoptosis, indicating the importance of PPARα/RXRα in regulating Wee 1-mediated Cdc2/cyclin B1 expression for cells to enter into mitosis. WY-14,643 treatment also induced cholestasis and liver injury, which is evidenced by induction of alanine aminotransferase, alkaline phosphatase, and hepatic bile acid levels in WT mice. Hepatocyte RXRα deficiency protected the mice from WY-14,643-induced liver injury. WY-14,643-mediated induction of the small heterodimer partner, Mrp3, and Cyp3a11 levels was greater in hepatocyte RXRα-null than in WT mouse livers suggesting enhanced repression of bile acid synthesis and increased efflux of bile acids into blood for renal excretion as well as hydroxylation of bile acids because of hepatocyte RXRα deficiency. These data establish a crucial role of hepatocyte RXRα in regulating WY-14,643-mediated cell cycle progression as well as bile acid homeostasis.
    Language English
    Dates of publication 2009-0403
    Size p. 9321-9330.
    Publishing place American Society for Biochemistry and Molecular Biology
    Document type Article
    ZDB-ID 2997-x
    ISSN 1083-351X ; 0021-9258
    ISSN (online) 1083-351X
    ISSN 0021-9258
    Database NAL-Catalogue (AGRICOLA)

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  5. Article: Antioxidant properties of Thonningianin A, isolated from the African medicinal herb, Thonningia sanguinea.

    Gyamfi, Maxwell Afari / Aniya, Yoko

    Biochemical pharmacology

    2002  Volume 63, Issue 9, Page(s) 1725–1737

    Abstract: The antioxidant properties of Thonningianin A (Th A), an ellagitannin, isolated from the methanolic extract of the African medicinal herb, Thonningia sanguinea were studied using the NADPH and Fe2+/ascorbate-induced lipid peroxidation (LPO), electron ... ...

    Abstract The antioxidant properties of Thonningianin A (Th A), an ellagitannin, isolated from the methanolic extract of the African medicinal herb, Thonningia sanguinea were studied using the NADPH and Fe2+/ascorbate-induced lipid peroxidation (LPO), electron spin resonance spectrometer and the deoxyribose assay. Th A at 10 microM inhibited both the NADPH and Fe2+/ascorbate-induced LPO in rat liver microsomes by 60% without inhibitory effects on cytochrome P450 activity. Th A was similar to the synthetic antioxidant, tannic acid, as an inhibitor of both the NADPH and Fe2+/ascorbate-induced LPO but potent than gallic acid, vitamin C and vitamin E. While Th A poorly scavenged the hydroxyl radical generated by the Fenton reaction it dose-dependently scavenged 1,1-diphenyl-2-picrylhydrazyl, superoxide anion and peroxyl radicals with IC50 of 7.5, 10 and 30 microM, respectively. Furthermore, Th A showed inhibitory effects on the activity of xanthine oxidase with an IC50 of 30 microM. In the deoxyribose assay both T. sanguinea and its methanolic component Th A showed only site-specific (Fe3+ + H2O2) but not non-site-specific (Fe3+ + EDTA + H2O2) hydroxyl radical scavenging suggesting chelating ability for iron ions. Spectroscopic studies showed that Th A enhanced absorbance in the visible region in the presence of Fe2+ ions. These results indicate that the antioxidant properties of Th A involve radical scavenging, anti-superoxide formation and metal chelation.
    MeSH term(s) Animals ; Antioxidants/isolation & purification ; Antioxidants/pharmacology ; Chelating Agents/isolation & purification ; Chelating Agents/pharmacology ; Edetic Acid/chemistry ; Free Radicals/metabolism ; Hydrolyzable Tannins ; Lipid Peroxidation/drug effects ; Male ; Medicine, African Traditional ; Microsomes, Liver/drug effects ; Microsomes, Liver/metabolism ; Molecular Conformation ; Plants, Medicinal/chemistry ; Rats ; Rats, Sprague-Dawley ; Reactive Oxygen Species/metabolism ; Tannins/isolation & purification ; Tannins/pharmacology
    Chemical Substances Antioxidants ; Chelating Agents ; Free Radicals ; Hydrolyzable Tannins ; Reactive Oxygen Species ; Tannins ; thonningianin A ; Edetic Acid (9G34HU7RV0)
    Language English
    Publishing date 2002-05-01
    Publishing country England
    Document type Journal Article
    ZDB-ID 208787-x
    ISSN 1873-2968 ; 0006-2952
    ISSN (online) 1873-2968
    ISSN 0006-2952
    DOI 10.1016/s0006-2952(02)00915-2
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article: The effect of ethanol, ethanol metabolizing enzyme inhibitors, and Vitamin E on regulating glutathione, glutathione S-transferase, and S-adenosylmethionine in mouse primary hepatocyte.

    Gyamfi, Maxwell Afari / Wan, Yu-Jui Yvonne

    Hepatology research : the official journal of the Japan Society of Hepatology

    2006  Volume 35, Issue 1, Page(s) 53–61

    Abstract: We studied changes in the antioxidant systems involved in hepatoprotection after ethanol exposure in primary culture of mouse hepatocytes. Ethanol decreased glutathione (GSH) levels and the S-adenosylmethionine (SAMe) to S-adenosylhomocysteine (SAH) ... ...

    Abstract We studied changes in the antioxidant systems involved in hepatoprotection after ethanol exposure in primary culture of mouse hepatocytes. Ethanol decreased glutathione (GSH) levels and the S-adenosylmethionine (SAMe) to S-adenosylhomocysteine (SAH) ratio by 53% and 22%, respectively. Cytosolic glutathione S-transferase (GST) activity was significantly lower in ethanol exposed hepatocytes, which was accompanied by an increase in GST activity in the culture medium. When specific substrates for mu- and pi-class GST were utilized, ethanol significantly decreased the mu- and pi-class GST activity by 53% and 13%, respectively. Lipid peroxidation (LPO), assessed by the thiobarbituric acid assay, increased to 221% of control by ethanol and was potentiated by cyanamide, an aldehyde dehydrogenase inhibitor. The changes in LPO, cytosolic GST activity, GSH levels and SAMe/SAH ratio in ethanol exposed hepatocytes were completely or partially reversed by either Vitamin E or 4-methylpyrazole, an alcohol dehydrogenase (ADH) inhibitor. Retinoid X receptor alpha-deficient (RXRalpha KO) mice, which are more susceptible to ethanol-induced liver toxicity, have decreased pi-class GST (56%), mu-class GST (28%), and glutathione peroxidase (35%) activities compared with wild type. Taken together, primary hepatocyte provides a valuable model to analyze ethanol-induced oxidative stress. The inhibition of mu-class GST activity by ethanol and the decreased pi-class GST activity in RXRalpha KO mice implicate the importance of these isozymes in ethanol detoxification process.
    Language English
    Publishing date 2006-03-15
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 1387041-5
    ISSN 1386-6346 ; 0928-4346
    ISSN 1386-6346 ; 0928-4346
    DOI 10.1016/j.hepres.2006.02.003
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: The pathogenesis of ethanol versus methionine and choline deficient diet-induced liver injury.

    Gyamfi, Maxwell Afari / Damjanov, Ivan / French, Samuel / Wan, Yu-Jui Yvonne

    Biochemical pharmacology

    2007  Volume 75, Issue 4, Page(s) 981–995

    Abstract: The differences and similarities of the pathogenesis of alcoholic (ASH) and non-alcoholic steatohepatitis (NASH) were examined. Mice (six/group) received one of four Lieber-Decarli liquid diets for 6 weeks: (1) paired-fed control diet; (2) control diet ... ...

    Abstract The differences and similarities of the pathogenesis of alcoholic (ASH) and non-alcoholic steatohepatitis (NASH) were examined. Mice (six/group) received one of four Lieber-Decarli liquid diets for 6 weeks: (1) paired-fed control diet; (2) control diet with ethanol (ethanol); (3) paired-fed methionine/choline deficient (MCD) diet; and (4) MCD plus ethanol (combination). Hepatotoxicity, histology, and gene expression changes were examined. Both MCD and ethanol induced macrovesicular steatosis. However, the combination diet produced massive steatosis with minor necrosis and inflammation. MCD and combination diets, but not ethanol, induced serum ALT levels by 1.6- and 10-fold, respectively. MCD diet, but not ethanol, also induced serum alkaline phosphatase levels suggesting bile duct injury. Ethanol increased liver fatty acid binding protein (L-FABP) mRNA and protein levels. In contrast, the combination diet decreased L-FABP mRNA and protein levels and increased hepatic free fatty acid and lipid peroxide levels. Ethanol, but not MCD, reduced hepatic S-adenosylmethionine (SAM) and GSH levels. Hepatic TNFalpha protein levels were increased in all treatment groups, however, IL-6, a hepatoprotective cytokine which promotes liver regeneration was increased in ethanol-fed mice (2-fold), but decreased in the combination diet-treated mice. In addition, the combination diet reduced phosphorylated STAT3 and Bcl-2 levels. While MCD diet might cause bile duct injury and cholestasis, ethanol preferentially interferes with the SAM-GSH oxidative stress pathway. The exacerbated liver injury induced by the combination diet might be explained by reduced L-FABP, increased free fatty acids, oxidative stress, and decreased IL-6 protein levels. The combination diet is an efficient model of steatohepatitis.
    MeSH term(s) Animals ; Body Weight/drug effects ; Choline Deficiency/complications ; Diet ; Ethanol/toxicity ; Fatty Liver/etiology ; Fatty Liver/metabolism ; Fatty Liver/pathology ; Fatty Liver, Alcoholic/etiology ; Fatty Liver, Alcoholic/metabolism ; Fatty Liver, Alcoholic/pathology ; Gene Expression/drug effects ; Liver/drug effects ; Liver/metabolism ; Liver/pathology ; Liver Function Tests ; Male ; Methionine/deficiency ; Mice ; Mice, Inbred Strains ; Organ Size/drug effects ; RNA, Messenger/genetics ; Reverse Transcriptase Polymerase Chain Reaction
    Chemical Substances RNA, Messenger ; Ethanol (3K9958V90M) ; Methionine (AE28F7PNPL)
    Language English
    Publishing date 2007-10-18
    Publishing country England
    Document type Comparative Study ; Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 208787-x
    ISSN 1873-2968 ; 0006-2952
    ISSN (online) 1873-2968
    ISSN 0006-2952
    DOI 10.1016/j.bcp.2007.09.030
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article: Selective suppression of cytochrome P450 gene expression by the medicinal herb, Thonningia sanguinea in rat liver.

    Gyamfi, Maxwell Afari / Tanaka, Tatsuo / Aniya, Yoko

    Life sciences

    2004  Volume 74, Issue 14, Page(s) 1723–1737

    Abstract: The effect of the administration of Thonningia sanguinea (T. S.) on the abundance of individual components of the cytochrome P450 monooxygenase enzyme was examined using Western blotting and competitive reverse-transcriptase-polymerase chain reaction (RT- ...

    Abstract The effect of the administration of Thonningia sanguinea (T. S.) on the abundance of individual components of the cytochrome P450 monooxygenase enzyme was examined using Western blotting and competitive reverse-transcriptase-polymerase chain reaction (RT-PCR). We also investigated the time-course of inhibition of T. S. on drug metabolizing enzymes. A single intraperitoneal dose of T. S. extract (5 ml/kg) suppressed CYP, cytochrome b5 and NADPH-CYP reductase activity by 45%, 34% and 22% respectively 24 h after T. S. administration. While T. S. did not have any significant effect on microsomal glutathione S-transferase activity, it inhibited p-nitrophenol hydroxylase (PNPH, CYP2E1) and 7-methoxyresorufin O-demethylase (MROD, CYP 1A2) activities by 37% and 32% respectively at 12 h post-T. S. administration. PNPH, erythromycin N-demethylase (ERDM, CYP 3A1/2) and MROD activities were inhibited by 28-36% 24 h after T. S. injection. Consistent with these observations, the levels of CYP2E1, CYP1A2 and CYP3A2 proteins were also suppressed 24 h post-T. S. administration. While CYP2E1 mRNA was unaffected by T. S. administration, CYP1A2 and CYP3A2 mRNAs were decreased by T. S. Cytosolic glutathione S-transferase activity was increased by 30%, 6 h after T. S injection. These data demonstrate that administration of T. S. differentially affect CYP isoforms in the liver of rats and that T. S. selectively suppresses CYP3A2 and CYP1A2 gene expression.
    MeSH term(s) Animals ; Balanophoraceae/chemistry ; Cytochrome P-450 Enzyme System/genetics ; Gene Expression Regulation, Enzymologic/drug effects ; Injections, Intraperitoneal ; Isoenzymes ; Liver/drug effects ; Liver/enzymology ; Male ; Microsomes, Liver/drug effects ; Microsomes, Liver/enzymology ; Plant Extracts/administration & dosage ; Plant Extracts/pharmacology ; RNA, Messenger/metabolism ; Rats ; Rats, Sprague-Dawley ; Reverse Transcriptase Polymerase Chain Reaction ; Time Factors
    Chemical Substances Isoenzymes ; Plant Extracts ; RNA, Messenger ; Cytochrome P-450 Enzyme System (9035-51-2)
    Language English
    Publishing date 2004-01-13
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 3378-9
    ISSN 1879-0631 ; 0024-3205
    ISSN (online) 1879-0631
    ISSN 0024-3205
    DOI 10.1016/j.lfs.2003.07.049
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Hepatic effects of a methionine-choline-deficient diet in hepatocyte RXRalpha-null mice.

    Gyamfi, Maxwell Afari / Tanaka, Yuji / He, Lin / Klaassen, Curtis D / Wan, Yu-Jui Yvonne

    Toxicology and applied pharmacology

    2009  Volume 234, Issue 2, Page(s) 166–178

    Abstract: Retinoid X receptor-alpha (RXRalpha) is an obligate partner for several nuclear hormone receptors that regulate important physiological processes in the liver. In this study the impact of hepatocyte RXRalpha deficiency on methionine and choline deficient ...

    Abstract Retinoid X receptor-alpha (RXRalpha) is an obligate partner for several nuclear hormone receptors that regulate important physiological processes in the liver. In this study the impact of hepatocyte RXRalpha deficiency on methionine and choline deficient (MCD) diet-induced steatosis, oxidative stress, inflammation, and hepatic transporters gene expression were examined. The mRNA of sterol regulatory element-binding protein (SREBP)-regulated genes, important for lipid synthesis, were not altered in wild type (WT) mice, but were increased 2.0- to 5.4-fold in hepatocyte RXRalpha-null (H-RXRalpha-null) mice fed a MCD diet for 14 days. Furthermore, hepatic mRNAs and proteins essential for fatty acid beta-oxidation were not altered in WT mice, but were decreased in the MCD diet-fed H-RXRalpha-null mice, resulting in increased hepatic free fatty acid levels. Cyp2e1 enzyme activity and lipid peroxide levels were induced only in MCD-fed WT mice. In contrast, hepatic mRNA levels of pro-inflammatory factors were increased only in H-RXRalpha-null mice fed the MCD diet. Hepatic uptake transporters Oatp1a1 and Oatp1b2 mRNA levels were decreased in WT mice fed the MCD diet, whereas the efflux transporter Mrp4 was increased. However, in the H-RXRalpha-null mice, the MCD diet only moderately decreased Oatp1a1 and induced both Oatp1a4 and Mrp4 gene expression. Whereas the MCD diet increased serum bile acid levels and alkaline phosphatase activity in both WT and H-RXRalpha-null mice, serum ALT levels were induced (2.9-fold) only in the H-RXRalpha-null mice. In conclusion, these data suggest a critical role for RXRalpha in hepatic fatty acid homeostasis and protection against MCD-induced hepatocyte injury.
    MeSH term(s) Animals ; Bile Acids and Salts/metabolism ; Blotting, Western ; Choline Deficiency/pathology ; Coloring Agents ; Cytochrome P-450 CYP2E1/biosynthesis ; Cytochrome P-450 CYP2E1/genetics ; Diet ; Fatty Acids/metabolism ; Hepatocytes/pathology ; Lipid Metabolism/genetics ; Lipid Metabolism/physiology ; Liver Cirrhosis/genetics ; Liver Cirrhosis/metabolism ; Liver Cirrhosis/pathology ; Liver Function Tests ; Methionine/deficiency ; Mice ; Mice, Knockout ; Multidrug Resistance-Associated Proteins/genetics ; Organic Anion Transporters, Sodium-Independent/genetics ; Oxidative Stress/physiology ; Retinoid X Receptor alpha/genetics ; Thiobarbituric Acid Reactive Substances/metabolism ; Up-Regulation/genetics
    Chemical Substances Abcc4 protein, mouse ; Bile Acids and Salts ; Coloring Agents ; Fatty Acids ; Multidrug Resistance-Associated Proteins ; Organic Anion Transporters, Sodium-Independent ; Retinoid X Receptor alpha ; Slco1b2 protein, mouse ; Thiobarbituric Acid Reactive Substances ; Methionine (AE28F7PNPL) ; Cytochrome P-450 CYP2E1 (EC 1.14.13.-)
    Language English
    Publishing date 2009-01-15
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ZDB-ID 204477-8
    ISSN 1096-0333 ; 0041-008X
    ISSN (online) 1096-0333
    ISSN 0041-008X
    DOI 10.1016/j.taap.2008.09.022
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article: Inhibition of glutathione S-transferases by thonningianin A, isolated from the African medicinal herb, Thonningia sanguinea, in vitro.

    Gyamfi, Maxwell Afari / Ohtani, Ikuko Ichiba / Shinno, Etsuki / Aniya, Yoko

    Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association

    2004  Volume 42, Issue 9, Page(s) 1401–1408

    Abstract: There is evidence that increased expression of glutathione S-transferase (EC: 2.5.1.18, GST) is involved in resistance of tumor cells against chemotherapeutic agents. In this study we investigated the inhibitory effects of thonningianin A (Th A), a novel ...

    Abstract There is evidence that increased expression of glutathione S-transferase (EC: 2.5.1.18, GST) is involved in resistance of tumor cells against chemotherapeutic agents. In this study we investigated the inhibitory effects of thonningianin A (Th A), a novel antioxidant isolated from the medicinal herb, Thonningia sanguinea on uncharacterized rat liver GST and human GST P1-1. Using 1-chloro-2,4-dinitrobenzene (CDNB) as substrate, rat liver cytosolic GST activity was inhibited by Th A in a concentration dependent manner with 50% inhibition concentration (IC50) of 1.1 microM. When Th A was compared with known potent GST inhibitors the order of inhibition was tannic acid>cibacron blue>hematin>Th A>ethacrynic acid with CDNB as substrate. Th A also exhibited non-competitive inhibition towards both CDNB and glutathione. Furthermore, using 1,2-dichloro-4-nitrobenzene, ethacrynic acid and 1,2-epoxy-3-(p-nitrophenoxy) propane as substrates Th A at 1.0 microM inhibited cytosolic GST by 2%, 12% and 36% respectively. Human GST P1-1 was also inhibited by Th A with an IC50 of 3.6 microM. While Th A showed competitive inhibition towards CDNB it exhibited non-competitive inhibition towards GSH of the human GST P1-1. These results suggest that Th A represents a new potent GST in vitro inhibitor.
    MeSH term(s) Animals ; Antioxidants/pharmacology ; Balanophoraceae/chemistry ; Cytosol/drug effects ; Cytosol/enzymology ; Dose-Response Relationship, Drug ; Enzyme Inhibitors/pharmacology ; Glutathione Transferase/antagonists & inhibitors ; Humans ; Hydrolyzable Tannins ; Inhibitory Concentration 50 ; Liver/drug effects ; Liver/enzymology ; Male ; Medicine, African Traditional ; Plants, Medicinal/chemistry ; Rats ; Rats, Sprague-Dawley ; Tannins/pharmacology
    Chemical Substances Antioxidants ; Enzyme Inhibitors ; Hydrolyzable Tannins ; Tannins ; thonningianin A ; Glutathione Transferase (EC 2.5.1.18)
    Language English
    Publishing date 2004-09
    Publishing country England
    Document type Journal Article
    ZDB-ID 782617-5
    ISSN 1873-6351 ; 0278-6915
    ISSN (online) 1873-6351
    ISSN 0278-6915
    DOI 10.1016/j.fct.2004.04.001
    Database MEDical Literature Analysis and Retrieval System OnLINE

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