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1.
Toxicol Lett ; 294: 37-43, 2018 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-29763686

RESUMO

Aldehyde reductase (Akr1a) has been reported to be involved in detoxification of reactive aldehydes as well as in the synthesis of bioactive compounds such as ascorbic acid (AsA). Because Akr1a is expressed at high levels in the liver and is involved in xenobiotic metabolism, our objective was to investigate the hepato-protective role of Akr1a in a thioacetamide (TAA)-induced hepatotoxicity model using Akr1a-deficient (Akr1a-/-) mice. Wild-type (WT) and Akr1a-/- mice were injected intraperitoneally with TAA and the extent of liver injury in the acute phase was assessed. Intriguingly, the extent of TAA-induced liver damage was less in the Akr1a-/- mice than in the WT mice. Biomarkers for the ER stress-induced apoptosis pathway were markedly decreased in the livers of Akr1a-/- mice, whereas AsA levels in plasma did not change significantly in any of the mice. In the liver, TAA is converted to reactive metabolites such as TAA S-oxide and then to TAA S, S-dioxide via the action of CYP2E1. In Akr1a-/- mice, CYP2E1 activity was relatively lower than WT mice at the basal level, leading to reactive TAA metabolites being produced at lower levels after the TAA treatment. The levels of liver proteins that were modified with these metabolites were also lower in the Akr1a-/- mice than the WT mice after the TAA treatment. Furthermore, after a lethal dose of a TAA challenge, the WT mice all died within 36 h, whereas almost all of the Akr1a-/- mice survived. These collective results suggest that Akr1a-/- mice are resistant to TAA-induced liver injury, and it follows that the absence of Akr1a might modulate TAA bioactivation.


Assuntos
Aldeído Redutase/metabolismo , Carcinógenos/toxicidade , Doença Hepática Induzida por Substâncias e Drogas/metabolismo , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Fígado/efeitos dos fármacos , Tioacetamida/toxicidade , Ativação Metabólica , Aldeído Redutase/genética , Animais , Apoptose/efeitos dos fármacos , Biomarcadores/sangue , Biomarcadores/metabolismo , Carcinógenos/metabolismo , Doença Hepática Induzida por Substâncias e Drogas/sangue , Doença Hepática Induzida por Substâncias e Drogas/etiologia , Doença Hepática Induzida por Substâncias e Drogas/patologia , Cruzamentos Genéticos , Citocromo P-450 CYP2E1/metabolismo , Resistência a Medicamentos , Fígado/metabolismo , Fígado/patologia , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Estresse Oxidativo/efeitos dos fármacos , Tioacetamida/metabolismo , Toxicocinética
2.
Toxicol Appl Pharmacol ; 291: 38-45, 2016 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-26701066

RESUMO

Obesity increases the risk of chronic liver diseases, including viral hepatitis, alcohol-induced liver disease, and non-alcoholic steatohepatitis. In this study, we investigated the effects of obesity in acute hepatic failure using a murine model of thioacetamide (TA)-induced liver injury. Genetically obese ob/ob mice, together with non-obese ob/+ littermates, were subjected to a single intraperitoneal injection of TA, and examined for signs of hepatic injury. ob/ob mice showed a significantly higher survival rate, lower levels of serum alanine aminotransferase and aspartate aminotransferase, and less hepatic necrosis and apoptosis, compared with ob/+ mice. In addition, ob/ob mice exhibited significantly lower levels of malondialdehyde and significantly higher levels of glutathione and antioxidant enzyme activities compared with their ob/+ counterparts. Bioactivation analyses revealed reduced plasma clearance of TA and covalent binding of [(14)C]TA to liver macromolecules in ob/ob mice. Together, these data demonstrate that genetically obese mice are resistant to TA-induced acute liver injury through diminished bioactivation of TA and antioxidant effects.


Assuntos
Doença Hepática Induzida por Substâncias e Drogas/genética , Doença Hepática Induzida por Substâncias e Drogas/prevenção & controle , Obesidade/genética , Tioacetamida/toxicidade , Animais , Doença Hepática Induzida por Substâncias e Drogas/metabolismo , Dose Letal Mediana , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Obesos , Obesidade/metabolismo , Tioacetamida/metabolismo
4.
J Mol Biol ; 426(20): 3442-53, 2014 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-24657767

RESUMO

Schistosomiasis, caused by the parasitic flatworm Schistosoma mansoni and related species, is a tropical disease that affects over 200 million people worldwide. A new approach for targeting eukaryotic parasites is to tackle their dynamic epigenetic machinery that is necessary for the extensive phenotypic changes during the life cycle of the parasite. Recently, we identified S. mansoni histone deacetylase 8 (smHDAC8) as a potential target for antiparasitic therapy. Here, we present results on the investigations of a focused set of HDAC (histone deacetylase) inhibitors on smHDAC8. Besides several active hydroxamates, we identified a thiol-based inhibitor that inhibited smHDAC8 activity in the micromolar range with unexpected selectivity over the human isotype, which has not been observed so far. The crystal structure of smHDAC8 complexed with the thiol derivative revealed that the inhibitor is accommodated in the catalytic pocket, where it interacts with both the catalytic zinc ion and the essential catalytic tyrosine (Y341) residue via its mercaptoacetamide warhead. To our knowledge, this is the first complex crystal structure of any HDAC inhibited by a mercaptoacetamide inhibitor, and therefore, this finding offers a rationale for further improvement. Finally, an ester prodrug of the thiol HDAC inhibitor exhibited antiparasitic activity on cultured schistosomes in a dose-dependent manner.


Assuntos
Antiparasitários/química , Proteínas de Helminto/química , Histona Desacetilases/química , Schistosoma mansoni/enzimologia , Tioacetamida/química , Animais , Antiparasitários/metabolismo , Antiparasitários/farmacologia , Apoptose/efeitos dos fármacos , Biocatálise/efeitos dos fármacos , Cristalografia por Raios X , Proteínas de Helminto/antagonistas & inibidores , Proteínas de Helminto/metabolismo , Inibidores de Histona Desacetilases/química , Inibidores de Histona Desacetilases/metabolismo , Inibidores de Histona Desacetilases/farmacologia , Histona Desacetilases/metabolismo , Humanos , Ácidos Hidroxâmicos/química , Ácidos Hidroxâmicos/metabolismo , Ácidos Hidroxâmicos/farmacologia , Concentração Inibidora 50 , Modelos Moleculares , Estrutura Molecular , Ligação Proteica , Estrutura Terciária de Proteína , Schistosoma mansoni/efeitos dos fármacos , Schistosoma mansoni/fisiologia , Esquistossomose mansoni/parasitologia , Tioacetamida/metabolismo , Tioacetamida/farmacologia , Vorinostat
5.
Chem Res Toxicol ; 25(9): 1955-63, 2012 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-22867114

RESUMO

The hepatotoxicity of thioacetamide (TA) has been known since 1948. In rats, single doses cause centrolobular necrosis accompanied by increases in plasma transaminases and bilirubin. To elicit these effects, TA requires oxidative bioactivation, leading first to its S-oxide (TASO) and then to its chemically reactive S,S-dioxide (TASO(2)), which ultimately modifies amine-lipids and proteins. To generate a suite of liver proteins adducted by TA metabolites for proteomic analysis and to reduce the need for both animals and labeled compounds, we treated isolated hepatocytes directly with TA. Surprisingly, TA was not toxic at concentrations up to 50 mM for 40 h. On the other hand, TASO was highly toxic to isolated hepatocytes as indicated by LDH release, cellular morphology, and vital staining with Hoechst 33342/propidium iodide. TASO toxicity was partially blocked by the CYP2E1 inhibitors diallyl sulfide and 4-methylpyrazole and was strongly inhibited by TA. Significantly, we found that hepatocytes produce TA from TASO relatively efficiently by back-reduction. The covalent binding of [(14)C]-TASO is inhibited by unlabeled TA, which acts as a "cold-trap" for [(14)C]-TA and prevents its reoxidation to [(14)C]-TASO. This in turn increases the net consumption of [(14)C]-TASO despite the fact that its oxidation to TASO(2) is inhibited. The potent inhibition of TASO oxidation by TA, coupled with the back-reduction of TASO and its futile redox cycling with TA, may help explain phenomena previously interpreted as "saturation toxicokinetics" in the in vivo metabolism and toxicity of TA and TASO. The improved understanding of the metabolism and covalent binding of TA and TASO facilitates the use of hepatocytes to prepare protein adducts for target protein identification.


Assuntos
Hepatócitos/metabolismo , Tioacetamida/análogos & derivados , Tioacetamida/metabolismo , Animais , Células Cultivadas , Citocromo P-450 CYP2E1/metabolismo , Inibidores do Citocromo P-450 CYP2E1 , Hepatócitos/efeitos dos fármacos , L-Lactato Desidrogenase/metabolismo , Masculino , Ratos , Ratos Sprague-Dawley , Tioacetamida/toxicidade
6.
Chem Res Toxicol ; 25(9): 1868-77, 2012 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-22667464

RESUMO

Thioacetamide (TA) is a well-known hepatotoxin in rats. Acute doses cause centrilobular necrosis and hyperbilirubinemia while chronic administration leads to biliary hyperplasia and cholangiocarcinoma. Its acute toxicity requires its oxidation to a stable S-oxide (TASO) that is oxidized further to a highly reactive S,S-dioxide (TASO(2)). To explore possible parallels among the metabolism, covalent binding, and toxicity of TA and thiobenzamide (TB), we exposed freshly isolated rat hepatocytes to [(14)C]-TASO or [(13)C(2)D(3)]-TASO. TLC analysis of the cellular lipids showed a single major spot of radioactivity that mass spectral analysis showed to consist of N-acetimidoyl PE lipids having the same side chain composition as the PE fraction from untreated cells; no carbons or hydrogens from TASO were incorporated into the fatty acyl chains. Many cellular proteins contained N-acetyl- or N-acetimidoyl lysine residues in a 3:1 ratio (details to be reported separately). We also oxidized TASO with hydrogen peroxide in the presence of dipalmitoyl phosphatidylenthanolamine (DPPE) or lysozyme. Lysozyme was covalently modified at five of its six lysine side chains; only acetamide-type adducts were formed. DPPE in liposomes also gave only amide-type adducts, even when the reaction was carried out in tetrahydrofuran with only 10% water added. The exclusive formation of N-acetimidoyl PE in hepatocytes means that the concentration or activity of water must be extremely low in the region where TASO(2) is formed, whereas at least some of the TASO(2) can hydrolyze to acetylsulfinic acid before it reacts with cellular proteins. The requirement for two sequential oxidations to produce a reactive metabolite is unusual, but it is even more unusual that a reactive metabolite would react with water to form a new compound that retains a high degree of chemical reactivity toward biological nucleophiles. The possible contribution of lipid modification to the hepatotoxicity of TA/TASO remains to be determined.


Assuntos
Muramidase/química , Fosfatidiletanolaminas/química , Tioacetamida/metabolismo , Animais , Células Cultivadas , Cromatografia em Camada Delgada , Hepatócitos/citologia , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Masculino , Espectrometria de Massas , Muramidase/metabolismo , Oxirredução , Fosfatidiletanolaminas/metabolismo , Ratos , Ratos Sprague-Dawley , Tioacetamida/análogos & derivados , Tioacetamida/química , Tioacetamida/toxicidade
7.
Eur J Clin Invest ; 42(6): 607-16, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22103576

RESUMO

BACKGROUND: We previously demonstrated that kaerophyllin, a lignan, isolated from a widely used traditional Chinese herb, Bupleurum scorzonerifolium, leading to the inhibition of hepatic stellate cells (HSCs) activation in vitro. This current study evaluated the in vivo role of kaerophyllin in protecting the liver against injury and fibrogenesis caused by thioacetamide (TAA) in rats and further explored the underlying mechanisms. MATERIALS AND METHODS: Liver fibrosis in Sprague-Dawley rats was induced by intraperitoneal injection of TAA (200 mg/kg) twice per week for 6 weeks. Animals were divided into five groups: vehicle control, TAA control, TAA + low dose kaerophyllin, TAA + high dose kaerophyllin and TAA + curcumin groups. Kaerophyllin (10 or 30 mg/kg) or curcumin (150 mg/mL) was given by gavage twice per day consecutively for 4 weeks starting 2 weeks after TAA injection. Rat HSCs were used to investigate the anti-inflammatory role of kaerophyllin against tumour necrosis factor α (TNF-α) in vitro. Peroxisome proliferator-activated receptor-γ (PPAR-γ) expression was knocked down in rat HSCs using PPAR-γ small interfering RNAs. RESULTS: Kaerophyllin significantly protected liver from injury by reducing serum aspartate transaminase and alanine transaminase levels and by improving the histological architecture and fibrosis score. In addition, kaerophyllin suppressed inflammation by reducing the mRNA of TNF-α, interleukin-1ß (IL-1ß) and monocyte chemoattractant protein-1 (MCP-1) genes. In HSCs, kaerophyllin elevated PPAR-γ activity and reduced TNF-α-stimulated mRNA levels of intracellular adhesion molecule-1 (ICAM-1), MCP-1 and IL-1ß genes, which were reversed by small interfering RNA knockdown of PPAR-γ gene. CONCLUSIONS: Our results demonstrated that kaerophyllin protected the rat liver from TAA-caused injury and fibrogenesis by suppressing hepatic inflammation and inhibiting HSC activation, possibly through upregulation of PPAR-γ expression.


Assuntos
Medicamentos de Ervas Chinesas/uso terapêutico , Células Estreladas do Fígado/efeitos dos fármacos , Lignanas/uso terapêutico , Cirrose Hepática/prevenção & controle , Fígado/efeitos dos fármacos , Tioacetamida/efeitos adversos , Alanina Transaminase/sangue , Animais , Aspartato Aminotransferases/sangue , Carcinógenos/metabolismo , Células Estreladas do Fígado/metabolismo , Fígado/metabolismo , Cirrose Hepática/induzido quimicamente , Cirrose Hepática/tratamento farmacológico , Masculino , Extratos Vegetais/metabolismo , Extratos Vegetais/uso terapêutico , Raízes de Plantas , Ratos , Ratos Sprague-Dawley , Tioacetamida/metabolismo
8.
Biochem Pharmacol ; 82(5): 556-65, 2011 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-21664898

RESUMO

BACKGROUND AND AIMS: Few drugs have been confirmed to be effective for fulminant hepatic failure (FHF). The purpose of this study was to prepare sterically stable liposomes (SSL) encapsulating hepatic stimulator substance (HSS) and determine their therapeutic effect on FHF. METHODS: HSS were encapsulated into SSL (HSS-SSL). FHF was induced in rats by thioacetamide (TAA) injection (400mg/kg, three times with a 24-h interval). The agents, including HSS-SSL, SSL, HSS, and sodium chloride (NS), were each injected intravenously 2h after the second and the third TAA injection. RESULTS: Freshly prepared HSS-SSL had a mean size of 93.59nm and the average encapsulation efficiency was 37.20%. HSS encapsulated in SSL showed a longer half life and more potent target to injured livers than free HSS. Twenty-four hours after the third TAA-injection, the survival rate of HSS-SSL-treated rats (80%) was significantly higher than that of rats treated with NS (20%), SSL (25%), or HSS (50%). Histopathologic examination showed that there was the least necrosis and inflammation in the livers of HSS-SSL-treated rats. The incidence of stage 3 or 4 hepatic encephalopathy in HSS-SSL-treated rats was significantly lower than that in rats treated with other agents. The serum pro-inflammatory cytokine levels and hepatic lipid peroxidation levels were both markedly reduced, while hepatocyte proliferative rate was markedly increased after HSS-SSL treatment. CONCLUSION: Encapsulation by SSL markedly improved the therapeutic effect of HSS on FHF in rats. Encapsulation by SSL may be an effective approach to enhance the therapeutic potency of drugs for FHF.


Assuntos
Falência Hepática Aguda/tratamento farmacológico , Peptídeos/administração & dosagem , Animais , Proliferação de Células/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Hepatócitos/patologia , Peptídeos e Proteínas de Sinalização Intercelular , Lipossomos , Falência Hepática Aguda/patologia , Masculino , Peptídeos/farmacocinética , Ratos , Ratos Sprague-Dawley , Tioacetamida/metabolismo , Tioacetamida/toxicidade , Distribuição Tecidual
9.
Chemosphere ; 83(9): 1201-7, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21489598

RESUMO

A novel coarsening route for extracellularly biosynthesized cadmium nanocrystals was investigated for the first time. In this process, the white rot fungus Coriolus versicolor was employed to take up cadmium ions and synthesize extracellular cadmium crystal particles. The coarsening of the particles was induced by thioacetamide under certain conditions. Scanning electron microscopy showed that the formed cadmium crystal particles were coarsened from about 100nm to 2-3µm. The corresponding energy-dispersive X-ray spectra confirmed the presence of proteins in the particles. The maximum removal efficiency of Cd(II) increased from 17% to 87%, and the corresponding sorption capacity of biomass increased from 4 to 24mgg(-1) with the completion of the coarsening process. The properties of the coarsened particles were also examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD analysis of fungal mycelial pellets embedded with the coarsened particles confirmed the formation of cubic crystalline cadmium sulfide particles. The TEM results suggest that the coarsened particles were composed of clusters of several smaller particles. The changes in the functional groups on the biomass surface were studied through Fourier transform infrared spectroscopy. Based on the results above, a possible mechanism for the formation and coarsening of cadmium crystal particle is also discussed.


Assuntos
Cádmio/metabolismo , Espaço Extracelular/metabolismo , Tioacetamida/metabolismo , Trametes/metabolismo , Cádmio/química , Cristalização , Microscopia Eletrônica de Transmissão , Tamanho da Partícula , Tioacetamida/química , Trametes/ultraestrutura , Difração de Raios X
10.
Biosci Biotechnol Biochem ; 74(4): 781-7, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20378990

RESUMO

Anoectochilus formosanus is used in traditional folk medicine as an hepatoprotective agent. The purpose of this study was to investigate the effects of a standardized aqueous extract of A. formosanus (SAEAF) on thioacetamide (TAA)-induced liver fibrosis. An in vitro study showed that the inhibitive effect of kinsenoside, a major component of SAEAF, on tumor necrosis factor alpha (TNF-alpha) secretion from Kupffer cells might be derived at least partly from downregulation of LPS-receptor Toll-like receptor 4 (TLR4) signaling. Hepatic fibrosis was produced by TAA (200 mg/kg, i.p.) 3 times per week for 12 weeks. Mice in the three TAA groups were treated daily with distilled water and SAEAF (1.0, 0.2 g/kg) via gastrogavage throughout the experimental period. The mice that received the SAEAF treatment had significantly reduced plasma alanine aminotransferase activity, relative liver weights, and hepatic hydroxyproline contents. A histological examination also confirmed that SAEAF reduced the degree of fibrosis caused by TAA treatment. RT-PCR analysis showed that SAEAF treatment reduced mRNA expression of collagen (alpha1)(I), lipopolysaccharide-binding protein, CD14, TLR4, and TNF receptor 1. An immunohistochemical examination also indicated that SAEAF reduced the number of CD68-positive cells (macrophages). In conclusion, oral administration of SAEAF significantly reduced TAA-induced hepatic fibrosis in mice, probably through inhibition of hepatic Kupffer cell activation.


Assuntos
Macrófagos do Fígado/metabolismo , Cirrose Hepática/patologia , Proteínas da Fase Aguda , Animais , Antígenos CD/metabolismo , Antígenos CD/farmacologia , Antígenos de Diferenciação Mielomonocítica/metabolismo , Proteínas de Transporte , Regulação para Baixo/efeitos dos fármacos , Hidroxiprolina/efeitos adversos , Hidroxiprolina/metabolismo , Lipopolissacarídeos/efeitos adversos , Lipopolissacarídeos/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Fígado/patologia , Cirrose Hepática/induzido quimicamente , Cirrose Hepática/metabolismo , Masculino , Medicina Tradicional , Glicoproteínas de Membrana , Camundongos , Camundongos Endogâmicos BALB C , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/efeitos dos fármacos , Tioacetamida/efeitos adversos , Tioacetamida/metabolismo , Tioacetamida/farmacologia , Receptor 4 Toll-Like/metabolismo , Fator de Necrose Tumoral alfa/metabolismo
11.
Peptides ; 31(1): 67-71, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19958806

RESUMO

Carnosine (beta-alanyl-L-histidine) is a dipeptide with antioxidant properties. Oxidative stress has been proposed to be involved in thioacetamide (TAA)-induced liver cirrhosis in rats, that is similar to human disease. In this study we aimed to investigate the role of carnosine on the development of TAA-induced cirrhosis. 200mg TAA/kg body weight has been given i.p. twice a week for three months to female wistar rats. Another group received same dose of TAA in the same pattern plus 2g carnosine/L of drinking water for three months. TAA administration resulted in hepatic fibrosis, significant increases in plasma transaminase activities as well as hepatic hydroxyproline and lipid peroxide levels, while liver glutathione (GSH) and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) protein expressions and activities decreased. Carnosine was found to behave as an antioxidant reducing malondialdehyde (MDA) and diene conjugate (DC) levels although it was not effective on increased transaminase activities and decreased antioxidants. It also did not affect the histopathological changes observed in TAA group. Thus our findings indicate that carnosine appears to attenuate peroxidation as an antioxidant itself but does not seem to prevent the development of TAA-induced cirrhotic process.


Assuntos
Antioxidantes/farmacologia , Carnosina/farmacologia , Cirrose Hepática/induzido quimicamente , Fígado/efeitos dos fármacos , Tioacetamida/toxicidade , Alanina Transaminase/metabolismo , Animais , Antioxidantes/metabolismo , Aspartato Aminotransferases/metabolismo , Carnosina/metabolismo , Feminino , Glutationa/metabolismo , Glutationa Peroxidase/metabolismo , Humanos , Fígado/citologia , Fígado/enzimologia , Fígado/patologia , Cirrose Hepática/metabolismo , Cirrose Hepática/patologia , Malondialdeído/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos Wistar , Superóxido Dismutase/metabolismo , Tioacetamida/administração & dosagem , Tioacetamida/metabolismo
12.
Toxicology ; 230(2-3): 105-16, 2007 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-17187915

RESUMO

Thioacetamide (TA) is bioactivated by CYP2E1 to TA sulfoxide (TASO), and to the highly reactive sulfdioxide (TASO(2)), which initiates hepatic necrosis by covalent binding. Previously, we have established that TA exhibits saturation toxicokinetics over a 12-fold dose range, which explains the lack of dose-response for bioactivation-based liver injury. In vivo and in vitro studies indicated that the second step (TASO-->TASO(2)) of TA bioactivation is less efficient than the first one (TA-->TASO). The objective of the present study was to specifically test the saturation of the second step of TA bioactivation by directly administering TASO, which obviates the contribution from first step, i.e. TA-->TASO. Male SD rats were injected with low (50mg/kg, ip), medium (100mg/kg) and high (LD(70), 200mg/kg) doses of TASO. Bioactivation-mediated liver injury that occurs in the initial time points (6 and 12h), estimated by plasma ALT, AST and liver histopathology over a time course, was not dose-proportional. Escalation of liver injury thereafter was dose dependent: low dose injury subsided; medium dose injury escalated upto 36h before declining; high dose injury escalated from 24h leading to 70% mortality. TASO was quantified in plasma by HPLC at various time points after administration of the three doses. With increasing dose (i.e., from 50 to 200mg/kg), area under the curve (AUC) and C(max) increased more than dose proportionately, indicating that TASO bioactivation exhibits saturable kinetics. Toxicokinetics and initiation of liver injury of TASO are similar to that of TA, although TASO-initiated injury occurs at lower doses. These findings indicate that bioactivation of TASO to its reactive metabolite is saturable in the rat as suggested by previous studies with TA.


Assuntos
Fígado/efeitos dos fármacos , Tioacetamida/análogos & derivados , Alanina Transaminase/sangue , Animais , Área Sob a Curva , Aspartato Aminotransferases/sangue , Doença Hepática Induzida por Substâncias e Drogas/etiologia , Doença Hepática Induzida por Substâncias e Drogas/metabolismo , Replicação do DNA/efeitos dos fármacos , Relação Dose-Resposta a Droga , Histocitoquímica , Fígado/patologia , Masculino , Microssomos Hepáticos/efeitos dos fármacos , Microssomos Hepáticos/metabolismo , Ratos , Ratos Sprague-Dawley , Tioacetamida/sangue , Tioacetamida/metabolismo , Tioacetamida/farmacocinética , Tioacetamida/toxicidade , Tioacetamida/urina , Timidina/metabolismo
13.
Appl Environ Microbiol ; 72(12): 7468-76, 2006 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-16997975

RESUMO

Information on bacterial thioamide metabolism has focused on transformation of the antituberculosis drug ethionamide and related compounds by Mycobacterium tuberculosis. To study this metabolism more generally, a bacterium that grew using thioacetamide as the sole nitrogen source was isolated via enrichment culture. The bacterium was identified as Ralstonia pickettii and designated strain TA. Cells grown on thioacetamide also transformed other thioamide compounds. Transformation of the thioamides tested was dependent on oxygen. During thioamide degradation, sulfur was detected in the medium at the oxidation level of sulfite, further suggesting an oxygenase mechanism. R. pickettii TA did not grow on thiobenzamide as a nitrogen source, but resting cells converted thiobenzamide to benzamide, with thiobenzamide S-oxide and benzonitrile detected as intermediates. Thioacetamide S-oxide was detected as an intermediate during thioacetamide degradation, but the only accumulating metabolite of thioacetamide was identified as 3,5-dimethyl-1,2,4-thiadiazole, a compound shown to derive from spontaneous reaction of thioacetamide and oxygenated thioacetamide species. This dead-end metabolite accounted for only ca. 12% of the metabolized thioacetamide. Neither acetonitrile nor acetamide was detected during thioacetamide degradation, but R. pickettii grew on both compounds as nitrogen and carbon sources. It is proposed that R. pickettii TA degrades thioamides via a mechanism involving consecutive oxygenations of the thioamide sulfur atom.


Assuntos
Ralstonia pickettii/metabolismo , Tioamidas/metabolismo , Cromatografia Líquida de Alta Pressão , Cromatografia Gasosa-Espectrometria de Massas , Genes de RNAr , Dados de Sequência Molecular , Oxigenases/metabolismo , RNA Ribossômico 16S/genética , Ralstonia pickettii/classificação , Ralstonia pickettii/genética , Ralstonia pickettii/crescimento & desenvolvimento , Análise de Sequência de DNA , Enxofre/metabolismo , Tioacetamida/metabolismo
14.
Chem Res Toxicol ; 18(4): 639-54, 2005 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15833024

RESUMO

We present here the potential of an integrated metabonomic strategy to deconvolute the biofluid metabolic signatures in experimental animals following multiple organ toxicities, using the well-known hepato- and nephrotoxin, thioacetamide. Male Han-Wistar rats were dosed with thioacetamide (150 mg/kg, n = 25), and urine, plasma, liver, and kidney samples were collected postdose for conventional NMR and magic angle spinning (MAS) NMR spectroscopy. These data were correlated with histopathology and plasma clinical chemistry collected at all time points. 1H MAS NMR data from liver and kidney were related to sequential 1H NMR measurements in urine and plasma using pattern recognition methods. One-dimensional 1H NMR spectra were data-reduced and analyzed using principal components analysis (PCA) to show the time-dependent biochemical variations induced by thioacetamide toxicity. From the eigenvector loadings of the PCA, those regions of the 1H NMR spectra, and hence the combinations of endogenous metabolites marking the main phase of the toxic episode, were identified. The thioacetamide-induced biochemical manifestations included a renal and hepatic lipidosis accompanied by hypolipidaemia; increased urinary excretion of taurine and creatine concomitant with elevated creatine in liver, kidney, and plasma; a shift in energy metabolism characterized by depleted liver glucose and glycogen; reduced urinary excretion of tricarboxylic acid cycle intermediates and raised plasma ketone bodies; increased levels of tissue and plasma amino acids leading to amino aciduria verifying necrosis-enhanced protein degradation and renal dysfunction; and elevated hepatic and urinary bile acids indicating secondary damage to the biliary system. This integrated metabonomic approach has been able to identify the tissue of origin for biomarkers present in the metabolic profiles of biofluids, following the onset and progression of a multiorgan pathology, and as such highlights its potential in the evaluation of embedded toxicity in novel drug candidates.


Assuntos
Rim/efeitos dos fármacos , Fígado/efeitos dos fármacos , Tioacetamida/toxicidade , Aminoácidos/metabolismo , Animais , Biomarcadores , Peso Corporal/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Rim/metabolismo , Rim/patologia , Metabolismo dos Lipídeos , Fígado/metabolismo , Fígado/patologia , Espectroscopia de Ressonância Magnética , Masculino , Nucleotídeos/metabolismo , Ratos , Ratos Wistar , Tioacetamida/metabolismo
15.
Mol Cell Biochem ; 211(1-2): 103-10, 2000 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11055553

RESUMO

The effect of thioacetamide (TA), an hepatotoxic and hepatocarcinogenic compound, on the expression and activity of the cytosolic enzyme glutathione-S-transferase (GST) was studied in rat liver. Four h following the administration of 14C-labeled thioacetamide (50 mg/Kg), several subunits of GST were found to be radioactively labeled. A single sublethal dose of TA (250 mg/Kg) decreased by three-fold the expression of class alpha GST at 24-48 h of treatment, but did not significantly affect the transcription of class mu GST. The activity of the enzyme toward 1-chloro-2,4-dinitrobenzene was mildly inhibited (66% of the control) by a 24 h TA treatment and gradually increased thereafter. It is proposed that the covalent binding of TA or its derivative to the GST subunits does not affect the activity of the enzyme. Nevertheless, GST activity inhibition is due to the deleterious effect of TA on GST transcription.


Assuntos
Glutationa Transferase/metabolismo , Fígado/efeitos dos fármacos , Fígado/enzimologia , Tioacetamida/farmacologia , África do Norte , Sequência de Aminoácidos , Animais , Radioisótopos de Carbono , Cromatografia em Gel , Citosol/enzimologia , Eletroforese em Gel de Poliacrilamida , Feminino , Glutationa Transferase/antagonistas & inibidores , Glutationa Transferase/genética , Dados de Sequência Molecular , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Alinhamento de Sequência , Tioacetamida/metabolismo , Fatores de Tempo , Transcrição Genética/efeitos dos fármacos
16.
Chem Biol Interact ; 124(2): 87-101, 2000 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-10670821

RESUMO

The ability of phenobarbital to induce the expression and activity of microsomal drug monooxygenases in the liver presents one of the most important issues in the field of chemical interactions and in the toxicity of xenobiotics. The model of rat liver injury induced by a single dose of thioacetamide (500 mg/kg intraperitoneally) was used to study the effect of phenobarbital (80 mg/kg/day intraperitoneally) for 5 days prior to thioacetamide. Serum parameters of liver injury such as aspartate aminotransferase activity, gamma-glutamyl transferase activity and the total bilirubin levels, as well as the activities of hepatic FAD and cytochrome P450 microsomal monooxygenases, were assayed in 2- and 12-month-old rats. Samples of blood and liver were obtained from controls (injected at 0 h with 0.5 ml of 0.9% NaCl) and at 12, 24, 48, 72 and 96 h of thioacetamide intoxication either to non-treated or phenobarbital pretreated rats. Potentiation of thioacetamide hepatotoxicity by phenobarbital pretreatment was demonstrated at morphological level, and by significant increases in the activities of serum aspartate aminotransferase and gamma-glutamyl transferase, and in the levels of total bilirubin. The extent of potentiation of thioacetamide-induced liver injury by phenobarbital pretreatment was similar in both age groups. Microsomal FAD monooxygenase activity, the enzyme responsible for thioacetamide biotransformation, was significantly enhanced (twofold) by phenobarbital pretreatment, and also underwent a further increase following thioacetamide, preceding the peak of necrosis. Cytochrome P450 monooxygenases were induced by phenobarbital pretreatment more than sixfold, and sharply decreased when phenobarbital was withdrawn and thioacetamide administered, showing at 48 h intoxication values close to basal. Phenobarbital pretreatment potentiated thioacetamide necrogenicity, and this potentiation was parallel to the induction of the microsomal FAD monooxygenase system, both by phenobarbital and by thioacetamide itself. The extent of thioacetamide-induced liver injury was significantly higher in 12-month-old rats, but the effect of phenobarbital pretreatment was similar in both age groups.


Assuntos
Fígado/efeitos dos fármacos , Fígado/enzimologia , Oxigenases/biossíntese , Fenobarbital/toxicidade , Tioacetamida/toxicidade , Fatores Etários , Animais , Aspartato Aminotransferases/sangue , Bilirrubina/sangue , Biotransformação , Sinergismo Farmacológico , Indução Enzimática/efeitos dos fármacos , Fígado/patologia , Masculino , Microssomos Hepáticos/efeitos dos fármacos , Microssomos Hepáticos/enzimologia , Necrose , Fenobarbital/administração & dosagem , Ratos , Ratos Wistar , Tioacetamida/administração & dosagem , Tioacetamida/metabolismo , gama-Glutamiltransferase/sangue
17.
Arch Biochem Biophys ; 349(2): 299-303, 1998 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-9448718

RESUMO

Jack bean urease catalyzes the hydrolysis of thiourea with a second-order rate constant (kcat/Km) of 1.6 (+/- 0.2) x 10(-3) M-1 S-1 at pH7, 25 degrees C. This value is lower than that for urea by a factor of 3 x 10(8). The corresponding substitution of S for O in acetamide reduces the kcat/Km value by only a factor of 33. This greater reactivity of the oxo compounds than of the corresponding thiono compounds, and the tighter binding of urea (Ks = 2.9 mM) than of either the guanidinium ion (Ki = 30 mM) or thiourea (Ki = 70 mM), suggests that the substrate chalcogen (S or O) is more likely to be stabilized in the transition state by coordination to the enzyme via a neutral hydrogen-bond donor (i.e., Brønsted acid catalysis) than by coordination via one of the active-site nickel ions (i.e., Lewis acid catalysis).


Assuntos
Fabaceae/enzimologia , Plantas Medicinais , Tioacetamida/metabolismo , Tioureia/metabolismo , Urease/metabolismo , Hidrólise , Cinética , Ligação Proteica , Especificidade por Substrato , Ureia/metabolismo
18.
Toxicology ; 31(1): 41-52, 1984 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-6729835

RESUMO

To evaluate the different contributions of either microsomal FAD-containing ( FADM ) or cytochrome P-450 dependent monooxygenases in the bioactivation and liver toxicity of thioacetamide-S-oxide ( TASO ) (a proximate metabolite of the liver toxin and carcinogen thioacetamide), this compound: (i) was given to rats pretreated with methimazole (a substrate and inhibitor of FADM ), SKF 525-A (an inhibitor of cytochrome P-450) and cobalt protoporphyrin IX (a synthetic porphyrin which induces a long-lasting depletion of the hepatic cytochrome P-450); and (ii) was added to liver microsomes performing oxidation of model FADM or cytochrome P-450 substrates. Whereas the prior administration of methimazole alleviated the TASO induced liver necrosis, SKF 525-A was almost ineffective. Also pretreatment with cobalt protoporphyrin IX prevented liver necrosis. However, this porphyrin derivative was found to depress both cytochrome P-450 dependent and the FADM dependent biotransformations. On the other hand, addition of TASO to liver microsomes in vitro induced changes in the kinetics of S-oxidation of thiobenzamide and of N-oxidation of dimethylaniline, whereas the O-deethylation of ethoxycoumarin was unchanged. The overall results show the necessity of TASO bioactivation by mixed-function monooxygenases for the toxic action to be apparent; at the same time, the findings suggest FADM as the system mainly involved in TASO metabolism.


Assuntos
Acetamidas/toxicidade , Fígado/efeitos dos fármacos , Oxigenases/fisiologia , Tioacetamida/toxicidade , Animais , Biotransformação , Sistema Enzimático do Citocromo P-450/fisiologia , Fígado/patologia , Masculino , Microssomos Hepáticos/enzimologia , Necrose , Proadifeno/farmacologia , Ratos , Ratos Endogâmicos , Tioacetamida/análogos & derivados , Tioacetamida/metabolismo
20.
Toxicol Lett ; 18(1-2): 127-31, 1983 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-6623535

RESUMO

Prior administration of chlorpromazine (CPZ), imipramine (IMP), mercaptoethylamine (MEA), 1-(1-naphthyl)2-thiourea (ANTU) or phenyl-thiocarbamide (PTC) but not 1,4-dithio-1-threitol (DTT), was able effectively to prevent most of thioacetamide (TAC) -induced liver necrosis. These and previous observations suggest that liver microsomal flavin-containing monooxygenase critically controls the process of activation of TAC to the ultimate necrogen.


Assuntos
Acetamidas/toxicidade , Fígado/efeitos dos fármacos , Tioacetamida/toxicidade , Animais , Biotransformação , Flavinas , Fígado/patologia , Masculino , Microssomos Hepáticos/enzimologia , Necrose , Ratos , Ratos Endogâmicos , Tioacetamida/metabolismo
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