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1.
Commun Biol ; 2: 378, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31633069

RESUMO

Metabolism is a major defense mechanism of the body against xenobiotic threats. Here we unravel a critical role of Bmal1 for circadian clock-controlled Cyp3a11 expression and xenobiotic metabolism. Bmal1 deficiency decreases the mRNA, protein and microsomal activity of Cyp3a11, and blunts their circadian rhythms in mice. A screen for Cyp3a11 regulators identifies two circadian genes Dbp and Hnf4α as potential regulatory mediators. Cell-based experiments confirm that Dbp and Hnf4α activate Cyp3a11 transcription by their binding to a D-box and a DR1 element in the Cyp3a11 promoter, respectively. Bmal1 binds to the P1 distal promoter to regulate Hnf4α transcriptionally. Cellular regulation of Cyp3a11 by Bmal1 is Dbp- and Hnf4α-dependent. Bmal1 deficiency sensitizes mice to toxicities of drugs such as aconitine and triptolide (and blunts circadian toxicity rhythmicities) due to elevated drug exposure. In summary, Bmal1 connects circadian clock and Cyp3a11 metabolism, thereby impacting drug detoxification as a function of daily time.

2.
Theranostics ; 9(18): 5122-5133, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31410205

RESUMO

Controlling bilirubin to a low level is necessary in physiology because of its severe neurotoxicity. Therefore, it is of great interest to understand the regulatory mechanisms for bilirubin homeostasis. In this study, we uncover a critical role for circadian clock in regulation of bilirubin detoxification and homeostasis. Methods: The mRNA and protein levels of Bmal1 (a core clock gene), metabolic enzymes and transporters were measured by qPCR and Western blotting, respectively. Luciferase reporter, mobility shift and chromatin immunoprecipitation were used to investigate transcriptional gene regulation. Experimental hyperbilirubinemia was induced by injection of bilirubin or phenylhydrazine. Unconjugated bilirubin (UCB) and conjugated bilirubin were assessed by ELISA. Results: We first demonstrated diurnal variations in plasma UCB levels and in main bilirubin-detoxifying genes Ugt1a1 and Mrp2. Of note, the circadian UCB levels were antiphase to the circadian expressions of Ugt1a1 and Mrp2. Bmal1 ablation abrogated the circadian rhythms of UCB and bilirubin-induced hepatotoxicity in mice. Bmal1 ablation also decreased mRNA and protein expressions of both Ugt1a1 and Mrp2 in mouse livers, and blunted their circadian rhythms. A combination of luciferase reporter, mobility shift, and chromatin immunoprecipitation assays revealed that Bmal1 trans-activated Ugt1a1 and Mrp2 through specific binding to the E-boxes in the promoter region. Further, Bmal1 ablation caused a loss of circadian time-dependency in bilirubin clearance and sensitized mice to chemical induced-hyperbilirubinemia. Moreover, bilirubin stimulated Bmal1 expression through antagonism of Rev-erbα, constituting a feedback mechanism in bilirubin detoxification. Conclusion: These data supported a dual role for circadian clock in regulation of bilirubin detoxification, generating circadian variations in bilirubin level via direct transactivation of detoxifying genes Ugt1a1 and Mrp2, and defending the body against hyperbilirubinemia via Rev-erbα antagonism. Thereby, our study provided a potential mechanism for management of bilirubin related diseases.

3.
Toxicol Lett ; 313: 188-195, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31284022

RESUMO

Brucine is one of the main bioactive and toxic constituents of the herb drug Semen Strychni. Here we aimed to determine dosing time-dependent hepatotoxicity of brucine, and to investigate the role of metabolism in generation of brucine chronotoxicity. Brucine was administered to wild-type or Npas2-/- (a clock disrupted model) mice at different circadian time points for toxicity and pharmacokinetic characterization. The hepatotoxicity was evaluated by plasma alanine aminotransferase and aspartate aminotransferase measurements and histopathological analysis. The role of Cyp3a11 in brucine metabolism was determined by chemical inhibition assays and Cyp3a11-overexpressing HEK293 cells. Hepatic circadian Cyp3a11 mRNA and protein levels were determined by qPCR and Western blotting, respectively. The toxicity of brucine was more severe in the light phase [Zeitgeber time (ZT) 2 and ZT8] than in the dark phase (ZT14 and ZT20). Chemical inhibition and substrate metabolism assays suggested Cyp3a11 as a significant contributor to brucine metabolism. The Cyp3a11 mRNA, protein and activity in the livers of wild-type mice displayed significant circadian fluctuations. Npas2 ablation markedly down-regulated Cyp3a11 mRNA, protein and activity, and abrogated their circadian rhythms. The circadian time differences in brucine pharmacokinetics and liver distribution were lost in Npas2-/- mice, so were the time differences in brucine hepatotoxicity. In conclusion, chronotoxicity of brucine was determined by circadian variations in Cyp3a11 metabolism. The findings have implications in improving brucine (and possibly Semen Strychni) efficacy via dosing time optimization.


Assuntos
Doença Hepática Induzida por Substâncias e Drogas/enzimologia , Ritmo Circadiano , Citocromo P-450 CYP3A/metabolismo , Fígado/efeitos dos fármacos , Fígado/enzimologia , Proteínas de Membrana/metabolismo , Fotoperíodo , Estricnina/análogos & derivados , Alanina Transaminase/sangue , Animais , Aspartato Aminotransferases/sangue , Fatores de Transcrição Hélice-Alça-Hélice Básicos/deficiência , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Doença Hepática Induzida por Substâncias e Drogas/sangue , Doença Hepática Induzida por Substâncias e Drogas/genética , Doença Hepática Induzida por Substâncias e Drogas/patologia , Ritmo Circadiano/genética , Cronoterapia Farmacológica , Células HEK293 , Humanos , Fígado/patologia , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microssomos Hepáticos/efeitos dos fármacos , Microssomos Hepáticos/enzimologia , Proteínas do Tecido Nervoso/deficiência , Proteínas do Tecido Nervoso/genética , Estricnina/administração & dosagem , Estricnina/metabolismo , Estricnina/farmacocinética , Estricnina/toxicidade
4.
Chem Biol Interact ; 308: 288-293, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31150629

RESUMO

Hypaconitine is an active and highly toxic constituent derived from Aconitum species. Here we aimed to determine the chronotoxicity of hypaconitine in mice, and to investigate a potential role of metabolism in hypaconitine chronotoxicity. Cardiac toxicity was assessed by measuring CK (creatine kinase) and LDH (lactate dehydrogenase) levels after hypaconitine administration to wild-type and Bmal1-/- (a clock disrupted model) mice at different times of day. The mRNA and protein levels of Cyp3a11 in mouse livers were determined by qPCR and western blotting, respectively. In vitro metabolism was assessed using liver microsomes. Pharmacokinetic study of hypaconitine was performed with wild-type mice. We observed injection time-dependent toxicity (i.e., a more severe toxicity during the light phase than the dark phase) for hypaconitine in mice. The chronotoxicity was attributed to a difference in systemic exposure of hypaconitine caused by time of day-dependent metabolism. Furthermore, circadian metabolism of hypaconitine was accounted for by the diurnal expression of Cyp3a11, a major enzyme for hypaconitine detoxification in the liver. Moreover, Bmal1 ablation in mice abolished the daily rhythm of Cyp3a11 expression and abrogated the time-dependency of hypaconitine toxicity. In conclusion, circadian Cyp3a11 metabolism contributed to chronotoxicity of hypaconitine in mice. This metabolism-based chronotoxicity would facilitate the formulation of best timing for drug administration.


Assuntos
Aconitina/análogos & derivados , Relógios Circadianos , Citocromo P-450 CYP3A/metabolismo , Fígado/efeitos dos fármacos , Proteínas de Membrana/metabolismo , Fatores de Transcrição ARNTL/deficiência , Fatores de Transcrição ARNTL/genética , Aconitina/metabolismo , Aconitina/farmacocinética , Aconitina/toxicidade , Animais , Creatina Quinase/sangue , Citocromo P-450 CYP3A/genética , Células HEK293 , Meia-Vida , Humanos , Fígado/metabolismo , Masculino , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microssomos Hepáticos/metabolismo , RNA Mensageiro/metabolismo
5.
Biomed Pharmacother ; 116: 108973, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31121485

RESUMO

Bilirubin is an endogenous substance derived from heme catabolism. In this study, we aimed to assess the anti-inflammatory activity of bilirubin, and to determine the mechanism thereof. The anti-inflammatory activity of bilirubin was evaluated using lipopolysaccharide (LPS)-treated peritoneal macrophages (PMs) and Raw264.7 cells, and mice with alum-induced peritonitis. The mRNA and proteins of NOD-like receptor family pyrin domain containing 3 (Nlrp3) and inflammatory cytokines were determined using qPCR and Western blotting, respectively. Distribution of phosphorylated (p) p65 [a NF-κB (nuclear factor-κB) subunit] in the cytoplasm and nucleus were evaluated by immunofluorescence analysis and electrophoretic mobility shift assay. Bilirubin prior to LPS treatment decreased protein expressions of Nlrp3, pro-interleukin (IL)-1ß and mature IL-1ß in PMs, whereas bilirubin post LPS treatment showed no effects. Bilirubin prior to LPS treatment dose-dependently repressed expressions of Nlrp3 and IL-1ß, and inhibited translocation of p-p65 to nucleus in Raw264.7 cells. Bilirubin treatment decreased myeloperoxidase activity and reduced the levels of inflammatory cytokines (i.e., IL-1ß, TNFα and IL-6) in lavage fluid in mice with alum-induced peritonitis. This was accompanied by a lower mortality rate. In addition, the mRNAs of Nlrp3 and IL-1ß in peritoneal exudates cells were decreased, and the levels of p-p65 and mature IL-1ß proteins were reduced. In conclusion, bilirubin acted on inflammation and alleviated alum-induced peritonitis through inactivation of Nlrp3 inflammasome.

6.
Nat Commun ; 9(1): 4246, 2018 10 12.
Artigo em Inglês | MEDLINE | ID: mdl-30315268

RESUMO

The roles of Rev-erbα and circadian clock in colonic inflammation remain unclarified. Here we show colon clock genes (including Rev-erbα) are dysregulated in mice with DSS-induced colitis. In turn, disruption of the circadian clock exacerbates experimental colitis. Rev-erbα-deficient mice are more sensitive to DSS-induced colitis, supporting a critical role of Rev-erbα in disease development. Further, Rev-erbα ablation causes activation of Nlrp3 inflammasome in mice. Cell-based experiments reveal Rev-erbα inactivates Nlrp3 inflammasome mainly at the priming stage. Rev-erbα directly represses Nlrp3 transcription through specific binding to the promoter region. Additionally, Rev-erbα represses p65 transcription and indirectly repressed Nlrp3 via the NF-κB pathway. Interestingly, Rev-erbα activation in wild-type mice by SR9009 attenuates DSS-induced colitis, whereas the protective effects are lost in Nlrp3-/- and Rev-erbα-/- mice. Taken together, Rev-erbα regulates experimental colitis through its repressive action on the NF-κB/Nlrp3 axis. Targeting Rev-erbα may represent a promising approach for prevention and management of colitis.

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